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The management of non-small cell lung cancer (NSCLC), specifically targeting the anaplastic lymphoma kinase (ALK) with tyrosine kinase inhibitors (TKIs), is challenged by the emergence of therapeutic resistance. Resistance mechanisms to ALK TKIs can be broadly classified into ALK-dependent and ALK-independent pathways. Here, we present a case with lung adenocarcinoma (LUAD) harboring an ALK rearrangement. The patient had developed resistance to sequential ALK TKI therapies, with an acquired ETV6-NTRK3 (E4:N14) fusion as a potential mechanism of ALK-independent resistance to lorlatinib. Subsequently, the patient was treated with the combination of brigatinib plus entrectinib and demonstrated a positive response, achieving an 8-month progression-free survival. Our case provides a potential treatment option for LUAD patients with ALK rearrangements and highlights the utility of next-generation sequencing (NGS) in uncovering genetic alterations that can guide the selection of effective treatment strategies. [ABSTRACT FROM AUTHOR]

Simple Summary: Gene fusions produce chimeric fusion proteins with unpredictable properties, many of which function as oncogenic drivers. ETV6-NTRK3 produces a constitutively active fusion kinase, which is not membrane bound like the endogenous NTRK3 kinase. Several studies have investigated the interactions of ETV6-NTRK3 over the years with few interactors being reported and some interactors reportedly being lost compared to the endogenous NTRK3. We utilize proximity labeling to produce the first proteomics level study on ETV6-NTRK3 close protein milieu and analyze the interactomes of all the four known ETV6-NTRK3 variants with functional kinase domains. Existing clinical literature shows that these four ETV6-NTRK3 variants occur at differing frequencies and originate in different tissues, with a "canonical" variant being more frequent and is also reported in other tissues. The ETV6-NTRK3 variants were found to have both similarities and differences in interactors, which might explain differences in reported frequencies and tissue specificities of the variants. Chromosomal translocations creating fusion genes are common cancer drivers. The oncogenic ETV6-NTRK3 (EN) gene fusion joins the sterile alpha domain of the ETV6 transcription factor with the tyrosine kinase domain of the neurotrophin-3 receptor NTRK3. Four EN variants with alternating break points have since been detected in a wide range of human cancers. To provide molecular level insight into EN oncogenesis, we employed a proximity labeling mass spectrometry approach to define the molecular context of the fusions. We identify in total 237 high-confidence interactors, which link EN fusions to several key signaling pathways, including ERBB, insulin and JAK/STAT. We then assessed the effects of EN variants on these pathways, and showed that the pan NTRK inhibitor Selitrectinib (LOXO-195) inhibits the oncogenic activity of EN2, the most common variant. This systems-level analysis defines the molecular framework in which EN oncofusions operate to promote cancer and provides some mechanisms for therapeutics. [ABSTRACT FROM AUTHOR]

Infantile fibrosarcoma (IFS) is a rare tumor in childhood characterized by a single, localized, painless mass that grows rapidly but has a relatively indolent biological behavior and a favorable prognosis. Eighty-five percent of infantile fibrosarcomas are associated with t (12;15) (p13;25) chromosomal translocation resulting in ETV6-NTRK3 gene fusion, which provides the target for targeted therapy. Here, we report a case of IFS in a newborn with a mass in the left lower extremity confirmed by imaging, histopathological examination, tissue FISH testing, and high-throughput sequencing to detect gene rearrangement. Based on gene fusion targeted drug testing results, the patient was treated with standard doses of larotrectinib, resulting in significant mass shrinkage with no adverse effects, demonstrating the treatment effect of targeted therapy. This case provides a reference for using larotrectinib in newborns with IFS. [ABSTRACT FROM AUTHOR]

Abstract Background Secretory breast carcinoma (SBC) is a rare malignant breast neoplasm with distinct histological features, including solid, microcystic, tubular, and rarely papillary structures, traditionally characterized by a t (12;15) (p13:q25) translocation, which usually leads to ETV6-NTRK3 fusion, suggesting an early event in tumorigenesis. Due to the rarity of this disease, very few genome sequencing studies have been performed on a series of cases, especially progressive cases. Methods Seven lesions from 5 patients diagnosed at the Third Affiliated Hospital of Soochow University from 2007 to 2021 were included. Clinicopathological features and prognosis/survival data were collected. Next-generation DNA sequencing was performed on six of the seven lesions. Results In total, 3/7 (42.9%) lesions demonstrated estrogen receptor (ER) expression, including weak, moderate to strong staining, and no lesion demonstrated progesterone receptor (PR) expression. There were no cases of human epidermal growth factor (HER2) overexpression, and the Ki-67 index was low. S-100 and pan-TRK protein were diffusely positively expressed in all cases. All lesions were characterized by a t(12;15) (p13:q25) translocation, leading to ETV6-NTRK3 fusion confirmed by fluorescence in situ hybridization (FISH). The sequencing results showed that ETV6-NTRK3 fusion was the main driver of early tumorigenesis, while SBC with invasive biological behavior had more complex genomic variation in which TERT promoter mutation was detected. Conclusions Immunohistochemical staining of a biomarker panel, including ER, PR, HER2, Ki-67, S-100 and pan-TRK, can be used as an auxiliary diagnostic tool, and FISH detection can be used as a diagnostic tool. ETV6-NTRK3 gene fusion involving multiple sites may drive tumorigenesis, while mutations in the TERT promoter region may be a factor driving tumor progression.

NTRK fusions are validated oncogenic drivers of various adult and pediatric tumor types, including thyroid cancer, and serve as a therapeutic target. Recently, tropomyosin receptor kinase (TRK) inhibitors, such as entrectinib and larotrectinib, display promising therapeutic efficacy in NTRK-positive solid tumors. Although some NTRK fusion partners have been identified in thyroid cancer, the spectrum of NTRK fusion is not fully characterized. In this study, a dual NTRK3 fusion was identified by targeted RNA-Seq in a 47-year-old female patient with papillary thyroid carcinoma. The patient harbors a novel in-frame fusion between NTRK3 exon 13 and AJUBA exon 2, co-existing with a known inframe fusion between ETV6 exon 4 and NTRK3 exon 14. The dual NTRK3 fusion was validated by Sanger sequencing and fluorescence in situ hybridization (FISH) but lack TRK protein expression as defined by pan-TRK immunohistochemistry (IHC). We supposed the pan-TRK IHC result to be falsely negative. In conclusion, we present the first case of a novel NTRK3-AJUBA fusion co-existing with a known ETV6-NTRK3 fusion in thyroid cancer. These findings extend the spectrum of translocation partners in NTRK3 fusion, and the effect of dual NTRK3 fusion on TRK inhibitor therapy and prognosis needs long-term follow-up. [ABSTRACT FROM AUTHOR]

The development, registration, and further use of entrectinib and larotrectinib for the treatment of tumors resulting from oncogenic stimulation of chimeric neurotrophin receptors (TRK) attracted much interest to the mechanisms of tumor cells resistance to TRK inhibitors during treatment. In the presented study, a cell line carrying the chimeric gene ETV6-NTRK3 (HFF-EN) was created on the basis of human fibroblasts. The transcription level of the chimeric ETV6-NTRK3 gene in HFF-EN was comparable to the transcription level of the household ACTB gene, the expression of the ETV6-NTRKA protein was confirmed by immunoblotting. A comparison of the dose—effect curves of fibroblasts and HFF-EN cells showed a ~38-fold increase in the sensitivity of HFF-EN to larotrectinib. To obtain a cell model of the resistance to larotrectinib in NTRK-dependent cancer, we used cell passages with a gradually increasing concentration of larotrectinib and obtained six resistant clones. p.G623E c.1868G>A mutation was found in five clones, and p.R582W c.1744C>T mutation, previously not described as a resistance mutation, was found in one clone showing significantly less resistance. These results can be further used for more complete understanding of the mechanisms of the resistance to TRK inhibitors and for the development of new drugs. [ABSTRACT FROM AUTHOR]

Background: The efficacy of entrectinib, a potent inhibitor of tropomyosin receptor kinases, c‐ros oncogene 1, and anaplastic lymphoma kinase has been demonstrated in neurotrophic receptor tyrosine kinase fusion‐positive pediatric and adult solid tumors. However, real‐world data on entrectinib therapy for salivary gland malignancies are limited. Methods: We describe a multicenter case series of four consecutive patients with ETV6‐NTRK3 fusion‐positive metastatic salivary secretory carcinoma (SSC) treated with entrectinib. Results: All patients had a prior history of systemic therapy with cytotoxic chemotherapy or immune checkpoint inhibitors. All patients achieved durable radiographic complete response. Adverse events included weight gain, dizziness, increase in creatine kinase level, and withdrawal pain, but were manageable by the interruption and dose reduction of entrectinib. Conclusion: Durable complete response was achieved with entrectinib in patients with ETV6‐NTRK3 fusion‐positive metastatic SSC. The clinical benefit of entrectinib supports the importance of routine screening for NTRK gene fusion in patients with SSC. [ABSTRACT FROM AUTHOR]

Purpose: Genotyping is fundamental in papillary thyroid cancer (PTC) and helps to enhance diagnosis and prognosis and determine appropriate treatments. The phenotype-genotype association in PTC was previously studied, with BRAF V600E characterizing classic PTC and tall-cell PTC and RAS mutations characterizing follicular-variant PTC. In clinic, some non-classical histological subtypes of PTC were also identified, however, their genotype remains unclear. In this study, we collected samples of these non-classical PTC after the exclusion of classic phenotypes and examined their phenotypes, genotype and the relationship between phenotype and genotype. Methods: We screened out non-classical PTC by excluding classical PTC from 1,059 different thyroid samples, and a total of 24 cases was obtained and described from the morphological features, which is rare in differentiated PTC. DNA/RNA sequencing was performed using 18 available samples to describe the genetic features. Results: PTC with the non-classical phenotype were characterized cuboidal to low columnar tumor cells with subtle nuclear features of PTC and without discernible nuclear elongation, concurrently with dense microfollicles, delicate papillae or solid nodules with delicate fibrovascular cores. They were associated with lymphatic vessel invasion (P<0.001) but not with a worse prognosis (P=0.791). Gene fusions were identified in 14 of 18 (77.8%) cases, including eight fusions of NTRK and six fusions of RET. The high percentage of fusions in this papillary thyroid cancer subgroup suggested a correlation of gene fusions with the phenotype that does not belong to the BRAF V600E-mutant or RAS-mutant group. Conclusions: Our study retrospectively screened a large cohort of different thyroid tissue samples, and presented the histopathological and genetic features of a non-classical phenotype of PTC from 24 patients. It may contribute to diagnose in PTC, and patients of these non-classical phenotype may benefit from targeted therapy, compared to a natural patient cohort without selection. [ABSTRACT FROM AUTHOR]

Simple Summary: Wild-type GISTs are generally not sensitive to tyrosine kinase inhibitors. Tropomyosin receptor kinase inhibitors have been approved to be effective in multiple cancers with neurotrophic tyrosine receptor kinase (NTRK) fusions. Although NTRK fusions are rare in wild-type GISTs, the unambiguous diagnosis can bring clinical benefits to the patients. The immunohistochemistry staining of Pan-TRK, next-generation sequencing or fluorescence in situ hybridization have been used to screen NTRK fusions in a few cases of wild-type GIST, and each technique has its advantages and drawbacks. This study aimed to identify NTRK fusions in wild-type GISTs with the above three methods and explore the clinicopathological and genetic features of GISTs with NTRK functions based on our patients and the literature. The findings from this study provide new evidence to establish a clinical protocol for screening GISTs with NTRK fusions and an overall view of the clinicopathological characteristics of GISTs with NTRK fusions. The most common mutations in gastrointestinal stromal tumors (GISTs) are KIT or PDGFRA mutations. Recently, neurotrophic tyrosine receptor kinase (NTRK) fusions have been reported in WT GISTs, which increased interest in introducing tropomyosin receptor kinase (TRK) inhibitors as treatments for GISTs with NTRK fusions. Hence, we aimed to screen NTRK fusions in WT GISTs; we used fluorescence in situ hybridization (FISH), next-generation sequencing (NGS), and immunohistochemistry (IHC) to screen NTRK fusions in 46 WT GISTs and evaluate each method. We further reviewed NTRK fusion-positive GISTs from the literature and performed clinical and pathological analyses; two GISTs with an ETV6-NTRK3 fusion (5%) were identified, while only one (50%) was positive for Pan-TRK expression. On the other hand, among the six GISTs with Pan-TRK-positive expression, only one (17%) harbored NTRK fusion. The literature review revealed the strong consistency between FISH and NGS and the limited value of Pan-TRK IHC in screening NTRK fusions in GISTs. In addition, the clinical and pathological analysis showed that GISTs with NTRK rearrangement occurred less frequently in the stomach, were more frequently larger in size, and the epithelioid type presented with a higher risk of recurrence. The NTRK3 fusion has been more common than the NTRK1 fusion in GISTs to date; our study identified two ETV6-NTRK3 fusions in 46 WT GISTs. Compared with FISH and IHC, NGS is preferred for screening WT GISTs, including NTRK rearrangements. However, since GISTs with NTRK fusions are rare, further studies including more samples and mechanistic investigations should be conducted in the future. [ABSTRACT FROM AUTHOR]

Background: Secretory breast carcinoma (SBC) is a rare malignant breast neoplasm with distinct histological features, including solid, microcystic, tubular, and rarely papillary structures, traditionally characterized by a t (12;15) (p13:q25) translocation, which usually leads to ETV6-NTRK3 fusion, suggesting an early event in tumorigenesis. Due to the rarity of this disease, very few genome sequencing studies have been performed on a series of cases, especially progressive cases. Methods: Seven lesions from 5 patients diagnosed at the Third Affiliated Hospital of Soochow University from 2007 to 2021 were included. Clinicopathological features and prognosis/survival data were collected. Next-generation DNA sequencing was performed on six of the seven lesions. Results: In total, 3/7 (42.9%) lesions demonstrated estrogen receptor (ER) expression, including weak, moderate to strong staining, and no lesion demonstrated progesterone receptor (PR) expression. There were no cases of human epidermal growth factor (HER2) overexpression, and the Ki-67 index was low. S-100 and pan-TRK protein were diffusely positively expressed in all cases. All lesions were characterized by a t(12;15) (p13:q25) translocation, leading to ETV6-NTRK3 fusion confirmed by fluorescence in situ hybridization (FISH). The sequencing results showed that ETV6-NTRK3 fusion was the main driver of early tumorigenesis, while SBC with invasive biological behavior had more complex genomic variation in which TERT promoter mutation was detected. Conclusions: Immunohistochemical staining of a biomarker panel, including ER, PR, HER2, Ki-67, S-100 and pan-TRK, can be used as an auxiliary diagnostic tool, and FISH detection can be used as a diagnostic tool. ETV6-NTRK3 gene fusion involving multiple sites may drive tumorigenesis, while mutations in the TERT promoter region may be a factor driving tumor progression. [ABSTRACT FROM AUTHOR]

Abstract Background Secretory carcinoma (SC) of the salivary gland is a recently described malignant tumor harboring characteristic ETV6-NTRK3 gene fusion. SC generally has a favorable clinical course, and is currently regarded as a low-grade carcinoma. However, a small subset of SCs demonstrates aggressive clinical features with histologically high-grade transformed morphology, the molecular pathogenesis of which has not yet been elucidated. In this study, we performed a clinicopathological and molecular genetic study of patients with SC of the head and neck displaying various clinical characteristics to investigate the differences of pathological and molecular genetics between low-grade and high-grade components of SC. Case presentation Three cases with SC of the head and neck, including a conventional low-grade SC and two high-grade transformed SCs are described. High-grade transformed SCs with histological features such as nuclear polymorphism, distinctive nucleoli and increased mitotic activity developed locoregional recurrence and distant metastasis. Immunohistochemical analysis revealed that low- and high-grade components showed different expression patterns for S-100 protein and mammaglobin, whereas all examined components were positive for p-STAT5. p53-positive cell population was markedly higher in one case with high-grade transformed SC. The proliferative activity of high-grade components was markedly increased, with the Ki-67 labeling index ranging up to 30–32%. A fluorescence in situ hybridization study with an ETV6 (12p13) break apart probe revealed split signals in the nuclei in all 3 cases. A targeted next-generation sequencing-based fusion assay demonstrated that all 6 clinical samples from the 3 patients showed the presence of the ETV6-NTRK3 fusion transcripts. One patient with high-grade transformed SC showed a dramatic clinical response to the pan-TRK inhibitor, entrectinib, for the treatment of locoregional recurrence and pulmonary metastasis. Conclusions High-grade transformed SC showed aggressive clinical and pathological features with increased Ki-67 labeling index. Molecular genetic study of gene rearrangement appears to be beneficial treatment as the presence of ETV6-NTRK3 translocation may represent a therapeutic target in SC, particularly the high-grade transformed type.

BACKGROUND: Secretory carcinoma (SC) of the salivary gland is a rare entity with limited published literature on cytomorphology. The authors present the largest cohort to date of SC fine‐needle aspiration (FNA) cases. METHODS: FNA cases of histologically confirmed SC were retrospectively retrieved from 12 academic institutions in the United States, Italy, Finland, and Brazil. The collated data included patient demographics, imaging findings, cytopathologic diagnoses according to the Milan System for Reporting Salivary Gland Cytopathology, cytomorphologic characteristics, and immunohistochemical/molecular profiles. RESULTS: In total, 40 SCs were identified (male‐to‐female ratio, 14:26) in patients with a mean age of 52 years (age range, 13‐80 years). Ultrasound imagining revealed a hypoechoic, ovoid, poorly defined, or lobulated mass. The most common primary site was the parotid gland (30 of 40 tumors). Regional lymph node metastasis (9 patients) and distant metastasis (4 patients; brain, liver, lungs, and mediastinum) were noted. Two patients died of disease. FNA smears were cellular and demonstrated mainly large, round cells with intracytoplasmic vacuoles or granules and round‐to‐oval nuclei with smooth nuclear contour, minimal irregularities, and prominent nucleoli arranged predominantly in clusters, papillary formations, and single cells. The background was variable and contained inflammatory cells, mucin, or proteinaceous material. The diagnoses were malignant (19 of 38 tumors; 50%), suspicious for malignancy (10 of 38 tumors; 26%), salivary gland neoplasm of uncertain malignant potential (7 of 38 tumors; 18%), and atypia of undetermined significance (2 of 38 tumors; 6%) according to the Milan System for Reporting Salivary Gland Cytopathology. Two malignant cases (2 of 40 tumors; 5%) were metastases. The neoplastic cells were immunoreactive for S100 (23 of 24 tumors), mammaglobin (18 of 18 tumors), GATA‐3 (13 of 13 tumors), AE1/AE3 (7 of 7 tumors), and vimentin (6 of 6 tumors). ETV6‐NTRK3 fusion was detected in 32 of 33 tumors by fluorescence in situ hybridization (n = 32) and next‐generation sequencing (n = 1). CONCLUSIONS: Familiarity with cytomorphologic features and the immunohistochemical/molecular profile of SC can enhance diagnostic accuracy.; Secretory carcinoma of the salivary gland, which may manifest with diverse cytomorphology, mammaglobin expression, and ETV6 rearrangement or ETV6‐NTRK3 fusion, was investigated along with cytomorphologic features to facilitate an accurate diagnosis. The results indicated that familiarity with these features and with the immunohistochemical/molecular profile of secretory carcinoma of the salivary gland enhanced diagnostic accuracy. [ABSTRACT FROM AUTHOR]

Abstract Background Secretory breast carcinoma is an uncommon subset of breast cancer that usually has a favorable outcome. Although initially described in children, it also occurs in adults where it may metastasize, possibly resulting in death. To date, only 20 cases of secretory breast carcinoma with distant metastases have been described. Case presentation A 42-year-old female presented with liver metastasis after modified radical mastectomy of the left breast in 2008 at 34 years of age. The liver metastasis was morphologically similar to the primary tumor. Pan-TRK and Fluorescence in situ hybridization showed a rearrangement in the ETV6 gene. She subsequently underwent adjuvant chemotherapy with a fatal outcome. Conclusions Although secretory breast carcinoma is usually associated with favorable outcomes, our study and reviews provide a novel insight into the genetic spectrum and treatment of secretory breast carcinoma showing reduced expression of hormone receptors, abnormal genomic profiles, and possible poor prognosis. Targeted therapy may curb clinically aggressive cases. Additional molecular investigations are needed to determine the links between specific mutations and poor prognosis.

INTRODUCTION: Primary renal fibrosarcoma is a relatively uncommon tumor in the urinary system of adults, in fact only 6 cases have been reported in the English literature so far worldwide. The etiology of renal fibrosarcoma is incompletely understood. It is still lacking in simple and specific tissue-based biomarkers to assist the diagnosis of renal fibrosarcoma. Among the previously reported cases in the literature, the ETV6-NTRK3 gene fusion could be detected in the congenital (or infantile) fibrosarcoma, and this rearrangement may play a vital role in initiation of congenital fibrosarcoma. However, the ETV6-NTRK3 expression has not been reported in adult-type fibrosarcoma in the literature so far. CASE PRESENTATION: A 66-year-old male patient admitted to our hospital because of chills, fever, and a right indwelling percutaneous nephrostomy catheter. Compared to normal kidney, the right renal had a thinner cortex and no function. After a week of anti-infective treatment, the patient underwent retroperitoneal laparoscopic right nephrectomy. The postoperative pathological result was fibrosarcoma of the right kidney. CONCLUSIONS: Aberrant expression of EVT6-NTRK3 may contribute to the development of renal fibrosarcoma. [ABSTRACT FROM AUTHOR]

Solid tumors resulting from oncogenic stimulation of neurotrophin receptors (TRK) by chimeric proteins are a group of rare tumors of various localization that respond to therapy with targeted drugs entrectinib and larotrectinib. The standard method for detecting chimeric TRK genes in tumor samples today is considered to be next generation sequencing with the determination of the prime structure of the chimeric transcripts. We hypothesized that expression of the chimeric tyrosine kinase proteins in tumors can determine the specific transcriptomic profile of tumor cells. We detected differentially expressed genes allowing distinguishing between TRK-dependent tumors papillary thyroid cancer (TC) from other molecular variants of tumors of this type. Using PCR with reverse transcription (RT-PCR), we identified 7 samples of papillary TC carrying a EVT6-NTRK3 rearrangement (7/215, 3.26%). Using machine learning and the data extracted from TCGA, we developed of a recognition function for predicting the presence of rearrangement in NTRK genes based on the expression of 10 key genes: AUTS2, DTNA, ERBB4, HDAC1, IGF1, KDR, NTRK1, PASK, PPP2R5B, and PRSS1. The recognition function was used to analyze the expression data of the above genes in 7 TRK-dependent and 10 TRK-independent thyroid tumors obtained by RT-PCR. On the test samples from TCGA, the sensitivity was 72.7%, the specificity — 99.6%. On our independent validation samples tested by RT-PCR, sensitivity was 100%, specificity — 70%. We proposed an mRNA profile of ten genes that can classify TC in relation to the presence of driver NTRK-chimeric TRK genes with acceptable sensitivity and specificity. [ABSTRACT FROM AUTHOR]

Secretory carcinoma of the thyroid gland is histologically and genetically similar to its mammary and salivary gland counterparts. Unlike differentiated thyroid carcinomas of follicular cell origin, thyroid SC is not a thyroglobulin-producing tumor and would not be amenable to radioactive iodine therapy. Instead, these carcinomas may respond to targeted therapy with TRK inhibitors, which further emphasizes the importance of their recognition among morphologically similar thyroid entities. Based on eleven cases reported to date, most primary thyroid SC tend to present as locally advanced malignancies and are characterized by frequent recurrences and long-term survival. High-grade histologic features, increased mitotic count and necrosis have been described but their impact on clinical course and outcome remains unclear. We hereby report the case of a primary SC with high-grade features arising in the thyroid of a 49-year-old man, who was treated with Larotrectinib for his second recurrence. The patient achieved a durable response that lasted for 18 months but then he continued to progress and died of disease 181 months after the diagnosis. [ABSTRACT FROM AUTHOR]

Secretory carcinoma (SC) of salivary gland, previously known as mammary analogue secretory carcinoma, is a rare low-grade malignancy harboring a diagnostic ETV6-NTRK3 gene fusion. SC of salivary gland shares histopathological, immunohistochemical and genetic characteristics with SC of the breast. There are several previous cytomorphological characterizations of SC of salivary gland reported in the literature. The most commonly reported patterns are of epithelial clusters with papillary architectural features, or of single dispersed epithelial cells on a background of abundant histiocytes. Tumor cells exhibit vacuolated eosinophilic cytoplasm and round to oval nuclei with regular nuclear contours and inconspicuous or small nucleoli. The cytomorphology of SC may closely mimic that of acinic cell carcinoma or low-grade mucoepidermoid carcinoma. Moreover, when cohesive epithelial clusters do not appear on the smears, it may be very difficult to distinguish dispersed tumor cells from histiocytes. In this article, we review the literature pertaining to SC cytomorphology and we report a fine needle aspiration biopsy case of SC in salivary gland showing well-defined intracytoplasmic hyaline globules, a feature that has not been previously reported. This novel cytomorphological feature may be helpful in distinguishing the tumor cells of SC from histiocytes and from other low-grade salivary gland tumors. [ABSTRACT FROM AUTHOR]

BackgroundAbout 10-15% of adult, and most pediatric, gastrointestinal stromal tumors (GIST) lack mutations in KIT, PDGFRA, SDHx, or RAS pathway components (KRAS, BRAF, NF1). The identification of additional mutated genes in this rare subset of tumors can have important clinical benefit to identify altered biological pathways and select targeted therapies.MethodsWe performed comprehensive genomic profiling (CGP) for coding regions in more than 300 cancer-related genes of 186 GISTs to assess for their somatic alterations.ResultsWe identified 24 GIST lacking alterations in the canonical KIT/PDGFRA/RAS pathways, including 12 without SDHx alterations. These 24 patients were mostly adults (96%). The tumors had a 46% rate of nodal metastases. These 24 GIST were more commonly mutated at 7 genes: ARID1B, ATR, FGFR1, LTK, SUFU, PARK2 and ZNF217. Two tumors harbored FGFR1 gene fusions (FGFR1-HOOK3, FGFR1-TACC1) and one harbored an ETV6-NTRK3 fusion that responded to TRK inhibition. In an independent sample set, we identified 5 GIST cases lacking alterations in the KIT/PDGFRA/SDHx/RAS pathways, including two additional cases with FGFR1-TACC1 and ETV6-NTRK3 fusions.ConclusionsUsing patient demographics, tumor characteristics, and CGP, we show that GIST lacking alterations in canonical genes occur in younger patients, frequently metastasize to lymph nodes, and most contain deleterious genomic alterations, including gene fusions involving FGFR1 and NTRK3. If confirmed in larger series, routine testing for these translocations may be indicated for this subset of GIST. Moreover, these findings can be used to guide personalized treatments for patients with GIST. Trial registration NCT 02576431. Registered October 12, 2015.

NTRK-rearranged thyroid carcinomas (NRTC) are rare. They are characterized by aggressive clinical behavior and distinct morphology. The presence of mucinous component in this subset of thyroid carcinomas is a finding that has never been described before. We report a 44-year-old female patient, who presented with a progressive enlarging anterior neck swelling for four months duration. Histopathologic examination of the resected thyroid gland demonstrated extensive infiltration of the left thyroid lobe by a carcinoma exhibiting dual morphology, partly composed of dilated glands filled with mucin and lined by mucous secreting cells, while other areas showed classical papillary thyroid carcinoma (PTC). Next Generation Sequencing (NGS) revealed a fusion between exon 4 of ETV6 gene and exon 14 of NTRK3 gene. Although rare, NRTCs should be correctly identified as they carry an actionable biomarker for emerging targeted therapies. Our case represents the first case of ETV6-NTRK3 translocated thyroid carcinoma with extensive mucinous features.

Secretory carcinoma (SC), previously known as mammary analogue secretory carcinoma, is a rare salivary gland neoplasm that typically presents as a slow-growing painless lesion in the head and neck. SC occurs mainly in adults but has been described in children with the youngest reported patient diagnosed at five years of age. In children the gender distribution has been reported as female to male ratio of 1:1.2. SC is generally considered a low-grade malignancy with characteristic morphological features and immunological profile. SC also harbors ETV6-NTRK3 fusion (t(12;15)(p13:q25)). Surgical resection with or without lymph node dissection is the standard treatment, with generally favorable clinical outcomes. Here we present a single institution case series of six patients (ages 9-21) with SC and a review of the previously described pediatric cases. Our small series showed male predominance in pediatric patients with predominantly low-grade and stage tumors. All cases underwent complete surgical resections and when follow up is available there was no evidence of recurrences or metastases. To the best of our knowledge, this is the only SC case series comprised exclusively of pediatric and youth patients. [ABSTRACT FROM AUTHOR]

Background: Secretory carcinoma (SC) of the salivary gland is a recently described malignant tumor harboring characteristic ETV6-NTRK3 gene fusion. SC generally has a favorable clinical course, and is currently regarded as a low-grade carcinoma. However, a small subset of SCs demonstrates aggressive clinical features with histologically high-grade transformed morphology, the molecular pathogenesis of which has not yet been elucidated. In this study, we performed a clinicopathological and molecular genetic study of patients with SC of the head and neck displaying various clinical characteristics to investigate the differences of pathological and molecular genetics between low-grade and high-grade components of SC. Case presentation: Three cases with SC of the head and neck, including a conventional low-grade SC and two high-grade transformed SCs are described. High-grade transformed SCs with histological features such as nuclear polymorphism, distinctive nucleoli and increased mitotic activity developed locoregional recurrence and distant metastasis. Immunohistochemical analysis revealed that low- and high-grade components showed different expression patterns for S-100 protein and mammaglobin, whereas all examined components were positive for p-STAT5. p53-positive cell population was markedly higher in one case with high-grade transformed SC. The proliferative activity of high-grade components was markedly increased, with the Ki-67 labeling index ranging up to 30–32%. A fluorescence in situ hybridization study with an ETV6 (12p13) break apart probe revealed split signals in the nuclei in all 3 cases. A targeted next-generation sequencing-based fusion assay demonstrated that all 6 clinical samples from the 3 patients showed the presence of the ETV6-NTRK3 fusion transcripts. One patient with high-grade transformed SC showed a dramatic clinical response to the pan-TRK inhibitor, entrectinib, for the treatment of locoregional recurrence and pulmonary metastasis. Conclusions: High-grade transformed SC showed aggressive clinical and pathological features with increased Ki-67 labeling index. Molecular genetic study of gene rearrangement appears to be beneficial treatment as the presence of ETV6-NTRK3 translocation may represent a therapeutic target in SC, particularly the high-grade transformed type. [ABSTRACT FROM AUTHOR]

Background. High-grade gliomas are characterized by a wide range of genetic abnormalities. The heterogeneous genomic landscape of pediatric high-grade gliomas allows identifying distinct subgroups of the disease in children and young adults. Most importantly, these subgroups differ by clinical course and prognosis, as well as treatment response to standard therapy.Objective: to assess the profile of molecular genetic markers of high-grade gliomas in children.Materials and methods. In the current study, we examine the frequency of H3F3A, Hist1H3B, BRAF, IDH1 / 2 mutations, the copy number alterations of CDKN2A / 2B genes and the expression of ETV6‑NTRK3 fusion gene in a cohort of 53 pediatric high-grade gliomas.Results. Driver mutations and CDKN2A / 2B deletions were observed in 24 (45 %) and 15 (28 %) of 53 tumors, respectively. Overall, the studied high-grade gliomas harbored 41 genetic aberrations including 24 (58.5 %) somatic missense mutations, 1 (2.4 %) genetic variant of unknown clinical significance, 1 (2.4 %) oncogenic fusion gene and 15 (36.6 %) deletions of the tumor suppressor genes.Conclusion. These findings point to the importance of molecular profiling of tumors for the optimal clinical care and development of new approaches to treatment aimed at molecular targets for personalized anticancer therapies.

Abstract Background While ETV6- NTRK3 fusion is common in infantile fibrosarcoma, NTRK1/3 fusion in pediatric tumors is scarce and, consequently, not well known. Herein, we evaluated for the presence of NTRK1/3 fusion in pediatric mesenchymal tumors, clinicopathologically and immunophenotypically. Methods We reviewed nine NTRK fusion-positive pediatric sarcomas confirmed by fluorescence in situ hybridization and/or next-generation sequencing from Seoul National University Hospital between 2002 and 2020. Results One case of TPR-NTRK1 fusion-positive intracranial, extra-axial, high-grade undifferentiated sarcoma (12-year-old boy), one case of LMNA-NTRK1 fusion-positive low-grade infantile fibrosarcoma of the forehead (3-year-old boy), one case of ETV6-NTRK3 fusion-positive inflammatory myofibroblastic tumor (IMT) (3-months-old girl), and six cases of ETV6-NTRK3 fusion-positive infantile fibrosarcoma (median age: 2.6 months, range: 1.6–5.6 months, M: F = 5:1) were reviewed. The Trk immunopositivity patterns were distinct, depending on what fusion genes were present. We observed nuclear positivity in TPR-NTRK1 fusion-positive sarcoma, nuclear membrane positivity in LMNA-NTRK1 fusion-positive sarcoma, and both cytoplasmic and nuclear positivity in ETV6-NTRK3 fusion-positive IMT and infantile fibrosarcomas. Also, the TPR-NTRK1 fusion-positive sarcoma showed robust positivity for CD34/nestin, and also showed high mitotic rate. The LMNA-NTRK1 fusion-positive sarcoma revealed CD34/S100 protein/nestin/CD10 coexpression, and a low mitotic rate. The IMT with ETV6-NTRK3 fusion expressed SMA. Six infantile fibrosarcomas with ETV6-NTRK3 fusion showed variable coexpression of nestin (6/6)/CD10 (4/5)/ S100 protein (3/6). Conclusions All cases of NTRK1 and NTRK3 fusion-positive pediatric tumors robustly expressed the Trk protein. A Trk immunopositive pattern and CD34/S100/nestin/CD10/SMA immunohistochemical expression may suggest the presence of NTRK fusion partner genes. LMNA-NTRK1 fusion sarcoma might be a low-grade subtype of infantile fibrosarcoma. Interestingly, more than half of the infantile fibrosarcoma cases were positive for S100 protein and CD10. The follow-up period of TPR-NTRK1 and LMNA-NTRK1 fusion-positive tumors are not enough to predict prognosis. However, ETV6-NTRK3 fusion-positive infantile fibrosarcomas showed an excellent prognosis with no evidence of disease for an average of 11.7 years, after gross total resection of the tumor.

Mammary analogue secretory carcinoma (MASC) of the salivary gland is a rare salivary cancer, histologically resembling to secretory carcinoma of the breast. In 2017 World Health Organization reported MASC is a new salivary cancer subtype. The aim of this article is to collect and analyze data about MASC, particularly clinical, histological and molecular profile, to evaluate targeted therapy effects. We discuss a case report of dramatic and durable response with entrectinib and the development of acquired resistance in an NTRK3-fusion positive salivary cancer, detected by next-generation sequencing. Next-generation sequencing as a comprehensive molecular profiling, that helps to investigate molecular profile of rare tumors and gives an opportunity to use an effective therapeutic options. Identifying ETV6-NTRK3 positive MASC provides a better prognosis for metastatic disease by using a novel effective targeted therapy with tyrosine kinase inhibitors (entrectinib, larotrectinib). Despite a durable and dramatic response, we showed an interesting case of the development of acquired resistance to tyrosine kinase inhibitors mediated by the appearance of a novel NTRK3 G623R mutation. Finally, we believe in great perspectives of comprehensive molecular profiling and targeted therapy for rare malignancies with NTRK gene fusions, including second-generation tyrosine kinase inhibitors.

The molecular signatures of many thyroid tumors have been uncovered. These discoveries have translated into clinical practice and are changing diagnostic and tumor classification paradigms. Here, the findings of recent studies are presented with special emphasis on how molecular insights are impacting the understating of RAS mutant thyroid nodules, Hürthel cell neoplasms, and unusual thyroid tumors, such as hyalinizing trabecular tumor, secretory carcinoma of the thyroid, and sclerosing mucoepidermoid carcinoma with eosinophilia. In addition, the utility of detecting actionable molecular alterations by immunohistochemistry in advanced and aggressive thyroid cancer is also discussed., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Infantile/congenital fibrosarcoma (IFS) is the most common soft tissue tumor in children less than one year of age. The most common anatomic site of IFS is in the extremities or trunk, and rarely in the abdomen or retroperitoneum. Approximately 70-90% of cases are characterized by a distinct t(12;15)(p13;q25) translocation resulting in an ETV6-NTRK3 gene fusion. As such, TRK inhibitors are considered frontline therapy in TRK-fusion positive IFS. The ETV6-NTRK3 fusion is also detected in congenital mesoblastic nephroma (CMN) and less frequently in myeloid leukemias, secretory breast carcinoma, and mammary-type secretory carcinoma of the skin and salivary glands. Infrequently, cases of tumors with IFS-like morphology without the characteristic ETV6-NTRK3 gene fusion have been identified. Herein, an ETV6-NTRK3 fusion negative spindle cell sarcoma with IFS-like morphology subjected to genomic profiling revealed a PDE10A-BRAF fusion, a fusion event that has been detected previously in an isolated case of undifferentiated infantile sarcoma. [ABSTRACT FROM AUTHOR]

Background: Secretory breast carcinoma is an uncommon subset of breast cancer that usually has a favorable outcome. Although initially described in children, it also occurs in adults where it may metastasize, possibly resulting in death. To date, only 20 cases of secretory breast carcinoma with distant metastases have been described. Case presentation: A 42-year-old female presented with liver metastasis after modified radical mastectomy of the left breast in 2008 at 34 years of age. The liver metastasis was morphologically similar to the primary tumor. Pan-TRK and Fluorescence in situ hybridization showed a rearrangement in the ETV6 gene. She subsequently underwent adjuvant chemotherapy with a fatal outcome. Conclusions: Although secretory breast carcinoma is usually associated with favorable outcomes, our study and reviews provide a novel insight into the genetic spectrum and treatment of secretory breast carcinoma showing reduced expression of hormone receptors, abnormal genomic profiles, and possible poor prognosis. Targeted therapy may curb clinically aggressive cases. Additional molecular investigations are needed to determine the links between specific mutations and poor prognosis. [ABSTRACT FROM AUTHOR]

We offer a case of a 22‐year‐old woman who presented with a painless breast mass. Physical examination of the breast was unrevealing other than a palpable mass in close proximity to the nipple areolar region. No lymphadenopathy was noticed in the axilla or supraclavicular region. Sonographic assessment was performed and the findings were classified as Breast Imaging Reporting and Data System category 4. Because of the proximity of the mass to the skin surface, an excisional biopsy was performed. Final pathology disclosed a 5‐mm invasive carcinoma. On pathologic examination, histopathology and immunophenotyping supported the diagnosis of secretory carcinoma; however, whether the origin was from the breast parenchyma or skin tissue was not clearly discernable. Therefore, the patient was scheduled for sentinel lymph node biopsy with plans for axillary dissection if positive. While the overall prognosis for secretory carcinoma is good, with a low chance of metastasis, any ambiguity in breast mass diagnosis should be discussed in a multidisciplinary tumor board and should be treated aggressively particularly in younger patients. [ABSTRACT FROM AUTHOR]

Secretory carcinoma (SC) is an uncommon salivary gland neoplasm of the oral cavity that microscopically may mimic acinic cell carcinoma (ACC) and mucoepidermoid carcinoma (MEC). This study describes a series of SC in minor glands with a literature review. We performed a retrospective search for oral SC, within the archives of the University of Florida, Oral Pathology and Surgical Pathology Biopsy services from 2010 to 2018. A total of 10 SCs were identified in the oral and maxillofacial region, four of which were in the minor salivary glands. The demographic, clinical, histological, and molecular findings were aggregated for all 4 cases. Patient age varied from 30 to 60 years, with an average of 45 years. Two cases each were in female and male patients. Two cases presented on the labial mucosa, and one each on the hard and soft palate. Immunohistochemical (IHC) staining showed mammaglobin positivity in all cases, GATA3 positivity in two cases, S100 positivity in three cases, and SOX10 positivity in only one case. Fluorescence in situ hybridization demonstrated positivity for ETV6-NTRK3 fusion in 4 cases. Although oral SC is rare, pathologists should be aware of the histologic overlap between the SC and other salivary gland neoplasms such as ACC and MEC. A judicious application of IHC staining would aid in diagnosis. SC should be considered in the differential diagnosis for intraoral salivary gland tumors. [ABSTRACT FROM AUTHOR]

• Novel 'ETV6-NTRK3 translocation-associated low-grade mucinous bronchial adenocarcinoma' • Biological behavior and response of this tumor type to NTRK targeted therapy is unknown • We advocate the use of molecular techniques in peribronchial tumors of uncertain type NTRK fusion genes have been found in several solid tumors, among which NSCLC and sarcoma. Novel NTRK translocation-related tumors are still being discovered. We report a 49-year-old patient with a mass in the left lower lung lobe that was resected. This specimen was analyzed and sequenced using targeted DNA next generation sequencing (NGS) and anchored-multiplex-PCR (AMP) targeted RNA NGS. On pathological evaluation, a peribronchial mucinous neoplasm with a unique morphology was found. RNA NGS analysis showed an ETV6-NTRK3 translocation in a low-grade mucinous bronchial adenocarcinoma. This entity represents a novel subtype of non-small cell lung cancer, which we would like to term ' ETV6-NTRK3 translocation-associated low-grade mucinous bronchial adenocarcinoma'. [ABSTRACT FROM AUTHOR]

Secretory carcinoma or mammary analog secretory carcinoma is an entity of salivary gland carcinoma that is characterized by the ETV6‐NTRK3 gene fusion. Although it is generally considered to be a low‐grade malignancy, some cases of secretory carcinoma with high‐grade transformation (SCHG) have been reported. We herein describe a case of SCHG composed almost exclusively of the high‐grade component. The patient presented with a growing mass in the buccal mucosa and underwent surgery. Tumor cells showing high‐grade nuclear atypia were arranged in solid or cribriform nests with comedo‐like necrosis. A differential diagnosis included high‐grade salivary gland carcinoma, such as salivary duct carcinoma. Immunohistochemically, tumor cells were focally positive for S‐100 and negative for mammaglobin and showed nuclear positivity for pan‐Trk. A reverse transcription polymerase chain reaction assay showed that the tumor harbored the ETV6‐NTRK3 gene fusion. A histological review of microscopic slides of the tumor did not reveal a typical secretory carcinoma component, except for a very focal area. We ultimately diagnosed this tumor as SCHG. This case underscores the importance of recognizing the histological spectrum of SCHG and the utility of pan‐Trk immunohistochemistry to detect secretory carcinoma, which may be targeted by tyrosine kinase inhibitors. [ABSTRACT FROM AUTHOR]

Abstract Background Secretory breast carcinoma is an exceptionally rare type of breast carcinoma. Only 5 cases of pure secretory carcinoma in situ have been reported in English literature. Herein, we reported a rare case of pure secretory breast carcinoma in situ. Case presentation The patient is a 38-year-old female with bloody discharge from the left nipple. Microscopically, the terminal-duct lobular units were enlarged and filled with tumor cells. The tumor cells were arranged in cystic, microcystic, solid and papillary pattern and formed a honeycomb-like appearance. The presence of intracellular and extracellular eosinphilic PAS-positive material was the most remarkable feature. Immunohistochemically, myoepithelial markers highlighted the complete presence of myoepithelial cells around the tumour nests. Tumour cells were strongly positive for S-100 and CK5/6, negative for ER, PR and HER2. Fluorescence in situ hybridization analysis showed ETV6-NTRK3 fusion. Conclusion Secretory carcinoma in situ shares the same morphological, immunohistochemical and molecular features with invasive secretory carcinoma except that the papillary growth pattern is more common in the introductal components. Cautions should be taken to distinguish secretory carcinoma in situ from other introductal lesions. Our report is an important supplement to the morphology spectrum of secretory breast carcinoma.

Secretory carcinoma (SC) of the salivary gland is a relatively newly described disease, separate from acinic cell carcinoma (ACC), which frequently displays ETV6-NTRK3 gene fusion. However, the differences between SC and ACC remain unclear. Here, histological reevaluation of 12 formerly diagnosed ACC cases was performed, which yielded a new diagnosis of SC in four cases due to a lack of obvious acinar-like cells. Immunohistochemically, phosphorylated signal transducer and activator of transcription 5 (p-STAT5) was expressed in SC but not in ACC, whereas discovered on GIST-1 (DOG1) was expressed in ACC but not in SC. Molecular analysis was possible in three SC cases, of which two showed the ETV6-NTRK3 fusion transcript on reverse-transcription polymerase chain reaction, as well as breaks in the ETV6 gene on fluorescence in situ hybridization. However, the remaining SC cases did not show this fusion transcript. Recently, several reports have suggested that SC might not be adequately diagnosed if the focus is placed solely on the ETV6-NTRK3 fusion gene due to genetic diversity. In this regard, immunohistochemistry of p-STAT5 and DOG1 is expected to be a useful alternative diagnostic tool to discriminate SC from ACC. [ABSTRACT FROM AUTHOR]

Secretory carcinoma (SC) is a rare salivary gland tumor that was first specified in the 2017 classification of head and neck cancers by the World Health Organization. Most SCs arise in the parotid gland and rarely in the minor salivary glands. We report a clinical case of SC under the buccal mucosa that was initially considered to be a benign tumor. The patient had noticed the mass under the buccal mucosa 2 months earlier. It was clinically diagnosed as a benign tumor and excised under local anesthesia. Histopathological examination revealed that tumor cells had eosinophilic cytoplasm without zymogen granules and proliferated in the form of micropapillary or cribriform. Immunohistochemical study revealed that tumor cells were positive for S-100, mammaglobin, and vimentin. Fluorescence in situ hybridization (FISH) revealed split of the ETV6 gene in tumor cells. These results confirmed that the tumor was a SC. No additional treatment was performed because the tumor was small and no residual tumor was observed. No recurrence or metastasis was observed during the 1.5 years of postoperative follow-up duration. [ABSTRACT FROM AUTHOR]

Secretory carcinoma (SC), previously described as mammary analogue secretory carcinoma, is a new subtype of salivary gland cancer that was added to the World Health Organization's classification of head and neck tumors in 2017. Although salivary gland cancer in the minor salivary glands is relatively rare, this disease is difficult to diagnose because of its various pathological tissue images and subtypes. In this report, we describe an SC tumor that occurred in the buccal mucosa and originated in the minor salivary glands. The patient was a 53-year-old man who noticed a mass in his right buccal mucosa. The lesion was initially clinically diagnosed as a benign tumor, but was later surgically excised from the patient under local anesthesia at another hospital. The tumor was pathologically diagnosed as malignant and some of the tumor remained following the initial surgery and the patient was referred to our department for additional surgical treatment. After surgical resection under general anesthesia, histopathological examination of the tumor suggested it was SC. Immunohistochemical staining revealed strongly positive staining for S100, vimentin, and mammaglobin and negative staining for DOG-1 and identify of the ETV6-NTRK3 gene fusion in the tumor cells. Although no subsequent local recurrence or metastasis was observed three years post-operation in this case, standardized treatment protocols and diagnostic methods are generally still lacking for SC. Salivary gland cancers in the minor salivary glands are relatively rare, but differential and accurate diagnosis is important. [ABSTRACT FROM AUTHOR]

Objectives: To identify oncogenic driver mutations in congenital mesoblastic nephroma (CMN) cases lacking ETV6-NTRK3 fusion and discuss their diagnostic value. Design: The institutional pathology database was queried for cases with a morphologic diagnosis of CMN. Cases positive for ETV6 rearrangement or with unavailable blocks were excluded. Four cases met the inclusion criteria and were sequenced by next-generation sequencing. Three additional cases were contributed by our collaborators. Results: Three of four internal cases harbor an EGFR kinase domain duplication (KDD), which is known to be oncogenic yet exceedingly rare in other histologies. All three outside cases are positive for EGFR alterations, including KDD in two and a splicing site mutation in one. The splicing site mutation is predicted to be EGFR activating. One of the outside cases was a retroperitoneal mass without a clear site of origin. A diagnosis of CMN is suggested based on exclusion of differential diagnoses by expert consultation and detection of EGFR KDD. Conclusions: EGFR activation, predominantly via EGFR KDD, is a common recurrent genetic alteration in CMN lacking NTRK3 fusions. CMN can be molecularly classified into NTRK3 fusion type, EGFR activation type and others.

Secretory carcinoma of the salivary gland is a newly recognized entity that morphologically resembles breast secretory carcinoma and has a characteristic t(12;15)(p13;q25) ETV6-NTRK3 translocation. Fluorescence in situ hybridization (FISH) or reverse transcription polymerase chain reaction (RT-PCR) analyses can detect the ETV6-NTRK3 fusion; however, both tests are expensive and not widely available. In this study, we aimed to determine whether pan-Trk immunohistochemistry (IHC) could detect ETV6-NTRK3 fusions as reliably as RT-PCR and FISH. We performed pan-Trk IHC in 70 salivary gland cancer samples, including secretory carcinomas, acinic cell carcinomas, and hybrid carcinomas. Nineteen tumors exhibited positive pan-Trk staining, including 16 secretory carcinomas, 2 hybrid carcinomas with a secretory carcinoma component, and 1 acinic cell carcinoma. Pan-Trk IHC staining was localized in the nucleus in 16 (84.2%) cases and in the cytoplasm and/or membrane in 3 (15.8%) cases. RT-PCR analysis for the ETV6-NTRK3 transcript was conducted in 45 samples; the fusion transcript was present in 11 of 12 secretory carcinomas and absent in 32 acinic cell carcinomas and 1 mucoepidermoid carcinoma. Pan-Trk IHC was positive in 10 of 11 salivary tumors that were positive for ETV6-NTRK3 by RT-PCR and negative in all 34 tumors that were negative for the fusion by RT-PCR. Therefore, in comparison with RT-PCR, pan-Trk IHC had a sensitivity of 90.9% and specificity of 100%. In conclusion, our data showed that pan-Trk IHC is a reasonable screening test for diagnosing secretory carcinoma of the salivary gland. [ABSTRACT FROM AUTHOR]

• ETV6::NTRK gene fusion in lung carcinoid cancer (AC) is firstly reported. • Biological behavior and response of AC to NTRK targeted therapy is unknown. • This report found that AC patients with NTRK gene fusion respond well to repotrectinib. Chromosomal rearrangements involving the neurotrophin kinase (NTRK) genes NTRK1, NTRK2 and NTRK3 with different fusion partners occur in non-small cell lung cancers (NSCLCs) and other solid tumors. Novel NTRK rearrangement-related tumors are still being discovered. Herin, we describe a male patient with a mass in the left upper lobe that was biopsied by bronchoscopy. This case was diagnosed with stage Ⅳ lung atypical carcinoid (AC) harboring the ETV6::NTRK3 gene fusion. He received 1st line treatment with everolimus lasting for 4 months. After chemotherapy failure, he received 3rd treatment with VC004 in a phase 1/2 study and achieved stable disease, but he stopped taking it due to intolerance. He subsequently received repotrectinib treatment and achieved a partial response of more than ten months. To the best of our knowledge, we reported the first case demonstrating anti-tumor activity of repotrectinib in a patient with AC carring an ETV6-NTRK3 gene fusion, indicating that repotrectinib may be an efficient therapeutic option for tumors with NTRK gene rearrangements. [ABSTRACT FROM AUTHOR]

Abstract Recent advances in molecular biology have revolutionized the concept of KIT/PDGFRA wild type (WT) gastrointestinal stromal tumors (GIST) than the past. Indeed, from being defined as GIST without KIT or PDGFRA mutations, we are now faced with the opposite scenario, where KIT/PDGFRA WT GIST are “positively” defined according to their specific molecular alterations. In particular, if until recently KIT/PDGFRA GIST without abnormalities of KIT, PDGFRA, SDH, and the RAS signaling pathway were referred as quadruple WT GIST, today also this small subset of GIST is emerging out as a group of heterogeneous distinct entities with multiple different molecular alterations. Therefore, given this still growing and rapidly evolving scenario, the progressive molecular fragmentation may inevitably lead over the time to the disappearance of KIT/PDGFRA WT GIST, destined to be singularly defined by their molecular fingerprint.

Aims: Secretory carcinoma of the breast (SCB) is a rare histological type of breast carcinoma with a generally indolent clinical behaviour. We aim to elucidate the clinical, pathological and molecular findings of SCB cases and identify characteristics associated with aggressive clinical courses. Methods and results: Fourteen patients with SCB were identified, including 12 women and two men, with a median age of 56 years (range = 8–81 years). Clinical data, histological diagnosis, molecular findings and follow‐up were reviewed. Eight patients presented with palpable masses and four patients with radiographic abnormalities. All cases were unilateral. Surgical procedures included excisional biopsies and ipsilateral mastectomies. In 10 cases, oestrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) results were obtained, with six cases positive for ER and three positive for PR. All cases lacked HER2 overexpression. Sentinel lymph node biopsy was performed in 10 cases, and two patients had axillary lymph node metastasis. Follow‐up ranged from 21 to 212 months (median = 70 months). Two patients developed distant metastasis of SCB. Molecular analysis of these aggressive tumours revealed amplification of the 16p13.3 locus, a TERT promotor mutation and loss of 9p21.3 locus. Review of the literature for SCB cases with distant metastasis was performed. Conclusions: Although SCBs are generally associated with a favourable prognosis, our study and review demonstrate that a subset of SCBs may develop distant metastases. Further studies are warranted to identify markers predictive of more aggressive clinical behaviour in this rare breast cancer subtype. [ABSTRACT FROM AUTHOR]

In the era of precision medicine, the identification of several predictive biomarkers and the development of innovative therapies have dramatically increased the request of tests to identify specific targets on cytological or histological samples, revolutionizing the management of the tumoral biomaterials. The Food and Drug Administration (FDA) has recently approved a selective neurotrophic tyrosine receptor kinase (NTRK) inhibitor, larotrectinib. Contemporarily, the development of multi-kinase inhibitors with activity in tumors carrying TRK fusions is ongoing. Chromosomal translocations involving the NTRK1, NTRK2, and NTRK3 genes result in constitutive activation and aberrant expression of TRK kinases in numerous cancer types. In this context, the identification of tumors harboring TRK fusions is crucial. Several methods of detection are currently available. We revise the advantages and disadvantages of different techniques used for identifying TRK alterations, including immunohistochemistry, fluorescence in situ hybridization, reverse transcriptase polymerase chain reaction, and next generation sequencing-based approaches. Finally, we propose a diagnostic algorithm based on histology and the relative frequency of TRK fusions in each specific tumor, considering also the economic feasibility in the clinical practice.

Objectives: E26 transformation-specific variant 6 gene (ETV6) is one of the most consistently rearranged genes in acute leukaemia. It encodes a principal hematopoietic transcription factor. Methods: We performed a systematic review focusing on the mechanisms responsible for etv6 acquisition, and its effect on the development of AML. We also review the Characteristics of ETV6 mutations and its fusion genes. Finally, for using ETV6 as a molecular target, we discuss future therapeutic approaches available to mitigate the associated disease. Results: ETV6 rearrangements often accompany other molecular mutations. Thirty-three distinct partner bands of ETV6 that contain various fusion genes were detected which plays a vital role in obtaining information about leukaemia genesis. RXDX-101 and PKC412 were reported to be inhibitors of ETV6-NTRK3. Discussion: Future researches are needed to explain how ETV6 mutations act within the microenvironment of leukemic cells and how it affects the progression of leukaemia. [ABSTRACT FROM AUTHOR]

Objectives: In 2010, a new subtype of salivary gland cancer (SGC), (mammary analogue) secretory carcinoma (SC), was defined, characterized by the ETV6-NTRK3 fusion gene. As clinical behavior and outcome data of this histological subtype tumor are still sparse, we aimed to describe the clinicopathological course and outcome of a series of translocation positive SC patients.Patient and Methods: We re-evaluated the pathological diagnosis of a subset of SGCs, diagnosed in 4 of 8 Dutch head and neck centers. Subsequently, tumors with a morphological resemblance to SC were tested for the ETV6-NTRK3 fusion gene using RT-PCR. Furthermore, patients prospectively diagnosed with SC were included. The clinical characteristics and outcomes were retrieved from the patient files.Results: Thirty-one patients with ETV6-NTRK3 fusion gene positive SC were included. The median age was 49 years, 17 patients (55%) were male. Eighteen tumors (58%) arose in the parotid gland. One patient presented with lymph node metastasis. All patients underwent tumor resection and 4 patients had a neck dissection. Four patients had re-resection and 15 patients (48%) received postoperative radiotherapy. One patient developed a local recurrence, no regional recurrences or distant metastases were observed. After a median follow-up of 49 months the 5- and 10-year overall survival were 95%, the 5- and 10-year disease free survival were 89%.Conclusion: The clinical course of SC is favorable with a low rate of locoregional recurrence and excellent survival. Given the low incidence of nodal metastases, elective neck treatment, i.e. surgery and/or radiotherapy, does not seem to be indicated. [ABSTRACT FROM AUTHOR]

Secretory carcinoma (SC) of the salivary gland is a new entity that shares the unique morphologic features and cytogenetic characteristics of the ETV6-NTRK3 fusion gene with its breast counterpart. Before identification of SC of the salivary gland, it was most frequently diagnosed as acinic cell carcinoma (AciCC). We retrospectively reviewed our own database of salivary gland tumors harboring microcystic and papillary architecture and/or secretory features that were originally diagnosed as AciCC. We selected nine cases of AciCC showing diffuse S-100 expression on immunohistochemistry (IHC). A recently diagnosed case of SC was included in the study as a reference sample. We performed IHC of S-100 and mammaglobin and ETV6 gene fluorescence in situ hybridization (FISH) in all cases. Seven cases were positive for both S-100 and mammaglobin, while five of the seven (71.4%) demonstrated ETV6 gene translocation by FISH. In the cases which did not co-express either S-100 or mammaglobin on IHC, ETV6 gene rearrangement was not shown on FISH. In conclusion, if a salivary gland tumor has morphologic features of SC with co-expression of S-100 and mammaglobin, ETV6 FISH can be performed to confirm the diagnosis of SC of the salivary gland. [ABSTRACT FROM AUTHOR]

Salivary gland-type tumors have been rarely described in the thyroid gland. Mammary Analog Secretory Carcinoma (MASC) is a recently defined type of salivary gland carcinoma characterized by a t(12;15)(p13;q25) resulting in an ETV6- NTRK3 fusion gene. We report 3 cases of MASC involving the thyroid gland without clinical evidence of a salivary gland or breast primary; the clinico-pathologic characteristics are reviewed. Assessment for rearrangement of the ETV6 (12p13) locus was conducted by fluorescence in situ hybridization (FISH) on representative FFPE sections using an ETV6 break apart probe (Abbott Molecular, Des Plaines, IL, USA). The patients were two females (52 and 55 years-old) and 1 male (74 years-old). The tumors were poorly circumscribed solid white tan nodules involving the thyroid. Histologically, they were invasive and showed solid, microcystic, cribriform, and tubular growth patterns composed of variably bland polygonal eosinophilic cells with vesicular nuclear chromatin and conspicuous nucleoli. All three cases showed metastasis to lymph nodes; one case showed lateral neck involvement. The tumor cells were positive for S100 and mammaglobin. GATA-3 and PAX-8 were positive in 2 cases, one of which only focally so. All three cases were negative for TTF-1 and thyroglobulin. Rearrangement of the ETV6 locus was confirmed in all cases and a diagnosis of MASC rendered for each case. A site of origin distinct from the thyroid gland was not identified, with a median follow up of 24 months. MASC may rarely involve the thyroid gland. The origin of these lesions is unknown; while an origin from ectopic salivary gland-type cells is entertained, a metastatic origin from an occult primary cannot be definitively excluded at this time. Given the histologic (follicular-like microcystic pattern with colloid-like secretions and papillary pattern), immunophenotypic (PAX-8), and even molecular overlap, MASC can be mistaken for papillary thyroid carcinoma and should be considered in the differential diagnosis of a thyroid mass. [ABSTRACT FROM AUTHOR]