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Oncocytic renal neoplasms are a major source of diagnostic challenge in genitourinary pathology; however, they are typically nonaggressive in general, raising the question of whether distinguishing different subtypes, including emerging entities, is necessary. Emerging entities recently described include eosinophilic solid and cystic renal cell carcinoma (ESC RCC), low-grade oncocytic tumor (LOT), eosinophilic vacuolated tumor (EVT), and papillary renal neoplasm with reverse polarity (PRNRP). A survey was shared among 65 urologic pathologists using SurveyMonkey.com (Survey Monkey, Santa Clara, CA, USA). De-identified and anonymized respondent data were analyzed. Sixty-three participants completed the survey and contributed to the study. Participants were from Asia (n = 21; 35%), North America (n = 31; 52%), Europe (n = 6; 10%), and Australia (n = 2; 3%). Half encounter oncocytic renal neoplasms that are difficult to classify monthly or more frequently. Most (70%) indicated that there is enough evidence to consider ESC RCC as a distinct entity now, whereas there was less certainty for LOT (27%), EVT (29%), and PRNRP (37%). However, when combining the responses for sufficient evidence currently and likely in the future, LOT and EVT yielded > 70% and > 60% for PRNRP. Most (60%) would not render an outright diagnosis of oncocytoma on needle core biopsy. There was a dichotomy in the routine use of immunohistochemistry (IHC) in the evaluation of oncocytoma (yes = 52%; no = 48%). The most utilized IHC markers included keratin 7 and 20, KIT, AMACR, PAX8, CA9, melan A, succinate dehydrogenase (SDH)B, and fumarate hydratase (FH). Genetic techniques used included TSC1/TSC2/MTOR (67%) or TFE3 (74%) genes and pathways; however, the majority reported using these very rarely. Only 40% have encountered low-grade oncocytic renal neoplasms that are deficient for FH. Increasing experience with the spectrum of oncocytic renal neoplasms will likely yield further insights into the most appropriate work-up, classification, and clinical management for these entities. [ABSTRACT FROM AUTHOR]

Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm known to occur at various soft tissue and visceral locations. Kidney is a rarely reported site for these tumors. Most of the SFTs described in the kidney exhibit a classical CD34-positive patternless spindle cell histology. Focal round cell morphology is seldom reported. Herein, we describe a 48-year-old male patient with renal SFT. This tumor had pure round cell morphology with a CD34−/STAT6+ immunophenotype. Fluorescent in situ hybridization and a multiplexed sequencing assay performed on an Illumina® HiSeq 4000 platform revealed NAB2 and STAT6 gene rearrangement. Renal tumors with round cell morphology are diagnostically challenging and SFT is not often considered in the differential diagnosis of a round cell tumor of the kidney. Moreover, a CD34-negative profile can be rather confounding while diagnosing such lesions. In such scenarios, a strong nuclear STAT6 immunostaining is extremely helpful in clinching the diagnosis. SFT should always be considered in the differential diagnosis of round cell tumors of the kidney due to significant diagnostic and therapeutic implications. [ABSTRACT FROM AUTHOR]

Background. Spindle cell/sclerosing rhabdomyosarcoma is a rare neoplasm and has an aggressive clinical course. Because of its rarity, we performed a multi-institutional collaboration to comprehend the overarching clinical, histopathological, and immunohistochemical characteristics of a cohort of spindle cell/sclerosing rhabdomyosarcoma. Materials and Methods. Forty-five patients with spindle cell/sclerosing rhabdomyosarcoma were identified. Demographics, clinical, histopathological, and immunohistochemistry data were reviewed and recorded. Results. The patients' age ranged from 1 to 85 years with a male to female ratio of 1.2:1. There were 15 children/adolescents and 30 adults. Eighteen (40%) tumors were located in the head and neck region. Twenty-four (53%) tumors displayed a bimorphic cellular arrangement with hypercellular areas having short, long, and sweeping fascicular and herringbone pattern, and hypocellular areas with stromal sclerosis and associated hyalinized and/or chondromyxoid matrix. Histomorphological differentials considered were leiomyosarcoma, malignant peripheral nerve sheath tumor, fibrosarcoma, nodular fasciitis, liposarcoma, synovial sarcoma, sarcomatoid carcinoma, solitary fibrous tumor, dermatofibrosarcoma protuberans, and schwannoma. Six tumors exhibited marked stromal sclerosis. The myogenic nature was confirmed by immunohistochemistry. Positivity for at least one skeletal muscle-associated marker (MyoD1 and/or myogenin) was observed. Conclusion. Spindle cell/sclerosing rhabdomyosarcoma diagnosis can be challenging as a number of malignant spindle cell neoplasm mimic this entity. Thus a correct diagnosis requires immunohistochemical work up with a broad panel of antibodies. In view of rarity of this neoplasm, further studies on a large cohort of patients with clinical follow-up data are needed for a better understanding of this tumor. [ABSTRACT FROM AUTHOR]

Objectives. : Accurate diagnosis of neuroblastoma may be challenging, especially with limited or inadequate specimen and at the metastatic sites due to overlapping imaging, histopathologic, and immunohistochemical (immunohistochemistry [IHC]; infidelity among various lineage-associated transcription factors eg FLI1, transducin-like enhancer 1, etc) features. GATA3 and ISL1 have recently been described as markers of neuroblastic differentiation. This study aims at determining the diagnostic utility of GATA3 and ISL1 in differentiating neuroblastoma from other pediatric malignant small round blue cell tumors. Methods. : We evaluated GATA3 and ISL1 expression in 74 pediatric small round blue cell tumors that included 23 NMYC -amplified neuroblastomas, 11 EWSR1 -rearranged round cell sarcomas, 7 SYT::SSX1 -rearranged synovial sarcomas, 5 embryonal rhabdomyosarcomas, 10 Wilms tumors (nephroblastomas), 7 lymphoblastic lymphoma, 7 medulloblastoma, and 4 desmoplastic small round cell tumor. Results. : All 23 neuroblastomas (moderate to strong staining in >50% of the tumor cells), 5 T-lymphoblastic lymphomas (moderate to strong staining in 40%-90% of the tumor cells), and 2 desmoplastic small round cell tumors (weak to moderate staining in 20%-30% of the tumor cells) expressed GATA3, while other tumors were negative. ISL1 immunoreactivity was observed in 22 (96%) neuroblastomas (strong staining in in >50% of the tumor cells, n = 17; moderate to strong staining in 26%-50% of the tumor cells, n = 5), 3 embryonal rhabdomyosarcoma (moderate to strong staining in 30%-85% of the tumor cells), 1 synovial sarcoma (weak staining in 20% of the tumor cells), and 7 medulloblastoma (strong staining in 60%-90% of the tumor cells). Other tumors were negative. Overall, GATA3 showed 86% specificity, 100% sensitivity, and 90% accuracy for neuroblastoma, with a positive predictive value (PPV) and negative predictive value (NPV) of 77% and 100%, respectively. ISLI showed 72% specificity, 96% sensitivity, and 81% accuracy for neuroblastoma, with a PPV and NPV of 67% and 97%, respectively. After the exclusion of T-lymphoblastic lymphoma and desmoplastic small round cell tumors, GATA3 had 100% specificity, sensitivity, accuracy, and PPV and NPV for neuroblastoma. Similarly, in pediatric small round blue cell tumors, ISL1 had 100% specificity, sensitivity, accuracy, PPV, and NPV for neuroblastoma, after embryonal rhabdomyosarcoma, synovial sarcoma, and medulloblastoma were excluded. Conclusions: GATA3 and ISL1 may be valuable in the diagnostic work-up of neuroblastoma and may reliably be used to support the neuroblastic lineage of pediatric small round blue cell tumors. Furthermore, dual positivity helps in challenging scenarios, when there is equivocal imaging, overlapping IHC features, limited specimen, and the lack of facility for a molecular work up. [ABSTRACT FROM AUTHOR]

Objectives Penile squamous cell carcinomas (PCs) are rare malignancies with a dismal prognosis in a metastatic setting; therefore, novel immunotherapeutic modalities are an unmet need. One such modality is the immune checkpoint molecule programmed cell death ligand 1 (PD-L1). We sought to analyze PD-L1 expression and its correlation with various clinicopathologic parameters in a contemporary cohort of 134 patients with PC. Methods A cohort of 134 patients with PC was studied for PD-L1 immunohistochemistry. The PD-L1 expression was evaluated using a combined proportion score with a cutoff of 1 or higher to define positivity. The results were correlated with various clinicopathologic parameters. Results Overall, 77 (57%) patients had positive PD-L1 expression. Significantly high PD-L1 expression was observed in high-grade tumors (P =.006). We found that 37% of human papillomavirus (HPV)–associated subtypes and 73% of other histotype tumors expressed PD-L1, while 63% of HPV-associated tumors and 27% of other histotype tumors did not (odds ratio, 1.35; P =.002 when compared for HPV-associated groups vs all others). Similarly, PD-L1–positive tumors had a 3.61-times higher chance of being node positive than PD-L1–negative tumors (P =.0009). In addition, PD-L1 high–positive tumors had a 5-times higher chance of being p16ink4a negative than PD-L1 low–positive tumors (P =.004). The PD-L1–positive tumors had a lower overall survival and cancer-specific survival than PD-L1–negative tumors. Conclusions Overall, PD-L1 expression is associated with high-grade and metastatic tumors. Lower PD-L1 expression is observed more frequently in HPV-associated (warty or basaloid) subtypes than in other, predominantly HPV-independent types. As a result, PD-L1 positivity, including higher expression, portends lower overall and cancer-specific survival. These data provide a rational for further investigating PD-L1–based immunotherapeutics in PC. [ABSTRACT FROM AUTHOR]

Primary renal synovial sarcoma is a rare aggressive mesenchymal neoplasm of the kidney that accounts for less than 1% of renal sarcomas. Herein, we describe the clinicopathologic and molecular findings of 14 renal synovial sarcoma patients in one of the largest case series to date and to our knowledge, the only renal synovial sarcoma series to use novel SS18-SSX IHC. Clinicopathologic, IHC, molecular, management, and follow-up data were reviewed and analyzed. Macroscopically, the tumors had either homogeneous, tan-white, and solid (n = 10), variegated and solid (n = 3), or variegated and solid-cystic (n = 1) cut surfaces. Spindle cell (n = 10), round cell (n = 3), and round to epithelioid morphologies (n = 1) were observed. SS18-SSX IHC was positive in all 14 tumors (diffuse, n = 10; multifocal, n = 2; focal, n = 2). All the tumors harbored SS18::SSX1/2 gene rearrangement. Metastases to the liver, brain, and lung (n = 1); liver and bone (n = 1); liver and diaphragm (n = 1) were identified. Adjuvant chemotherapy was administered in 11/12 patients. Follow-up was available for 10 patients (time period range: 5 to 24 months). Four patients died of disease, and six patients are alive with no recurrence or metastasis. As SS18-SSX IHC showed an excellent concordance with the FISH results, this may reliably be used in the IHC panel of spindle/round cell sarcomas of the kidney and as a molecular surrogate for renal synovial sarcoma, particularly in a resource-limited setting. Also, the tumors with focal SS18-SSX expression had lower break apart signals in the FISH assay (19% and 23% in two tumors with focal SS18-SSX IHC positivity). [ABSTRACT FROM AUTHOR]

Lipogenic differentiation in ependymoma is an infrequent occurrence with very few reported cases. The grading was done solely based on the histomorphology and molecular subtyping was not described in such ependymomas. New molecular classification divided ependymomas in nine different subgroups, of which supratentorial location tumor usually exhibits C11orf95-RELA, YAP1-MAMLD1, and YAP1-FAM118B fusion proteins. A 46-year-old female presented with headache and right-sided parapresis. Radilogy revealed a large intraxial left parietooccipital mass lesion, which histologically and immuohistochemically confirmed as anaplastic ependymoma with extensive lipogenic changes. The ependymal origin of the tumor was corroborated by the immunohistochemistry and ultrastructural studies. Molecular studies for C11orf95-RELA, YAP1-MAMLD1, and YAP1-FAM118B fusion proteins were negative. This is the first documentation of fusion negative supratentorial anaplastic ependymoma with lipogenic differentiation. This novel finding needs further reinforcement by similar studies to identify its impact on the disease outcome. [ABSTRACT FROM AUTHOR]

Meningeal Rosai-Dorfman disease, a type of sporadic Rosai-Dorfman disease, is a rare occurrence. A few cases are reported in the English literature with an adequate immunohistochemical workup. This entity clinically and radiologically mimics either a meningeal or a parenchymal neoplasm with meningeal extension, warranting a thorough histopathologic evaluation. A broad histologic differential necessitates a detailed immunohistochemical characterization to render a correct diagnosis that has significant therapeutic and prognostic implications. Herein, we report a case of isolated meningeal Rosai-Dorfman disease in a 50-years-old human immunodeficiency virus-positive male patient with an emphasis on the histopathology, immunoprofile, and differential diagnoses. [ABSTRACT FROM AUTHOR]

Low-grade oncocytic tumour (LOT) of the kidney has recently emerged as a potential novel tumour type. Despite similarity to oncocytoma or eosinophilic chromophobe renal cell carcinoma, it shows diffuse keratin 7 immunohistochemistry (IHC) and negative KIT (CD117), which differs from both. We aimed to identify the molecular characteristics of these tumours. Seventeen tumours (one male, 16 female, nine previously published) fitting the original description of this entity (solid eosinophilic cell morphology, often with areas of tumour cells loosely stretched in oedematous stroma, and the above IHC features) were analysed with a next-generation sequencing panel of 324 cancer-associated genes from formalin-fixed, paraffin-embedded tissue. All tumours harboured at least one alteration in either TSC1 (n = 7, 41%), TSC2 (n = 2, 12%), MTOR (n = 5, 29%) or PIK3CA (n = 4, 24%). Four tumours harboured a second alteration, including two NF2, one each in conjunction with MTOR and TSC2 alterations, one PTEN with TSC1 alteration and one tumour with both MTOR and TSC1 alterations. No other renal cancer Low-grade oncocytic tumour (LOT) of the kidney has recently emerged as a potential novel tumour type. Despite similarity to oncocytoma or eosinophilic chromophobe renal cell carcinoma, it shows diffuse keratin 7 immunohistochemistry (IHC) and negative KIT (CD117), which differs from both. We aimed to identify the molecular characteristics of these tumours. Seventeen tumours (one male, 16 female, nine previously published) fitting the original description of this entity (solid eosinophilic cell morphology, often with areas of tumour cells loosely stretched in oedematous stroma, and the above IHC features) were analysed with a next-generation sequencing panel of 324 cancer-associated genes from formalin-fixed, paraffin-embedded tissue. All tumours harboured at least one alteration in either TSC1 (n = 7, 41%), TSC2 (n = 2, 12%), MTOR (n = 5, 29%) or PIK3CA (n = 4, 24%). Four tumours harboured a second alteration, including two NF2, one each in conjunction with MTOR and TSC2 alterations, one PTEN with TSC1 alteration and one tumour with both MTOR and TSC1 alterations. No other renal cancer [ABSTRACT FROM AUTHOR]

Low‐grade oncocytic tumour (LOT) of the kidney has recently emerged as a potential novel tumour type. Despite similarity to oncocytoma or eosinophilic chromophobe renal cell carcinoma, it shows diffuse keratin 7 immunohistochemistry (IHC) and negative KIT (CD117), which differs from both. We aimed to identify the molecular characteristics of these tumours. Seventeen tumours (one male, 16 female, nine previously published) fitting the original description of this entity (solid eosinophilic cell morphology, often with areas of tumour cells loosely stretched in oedematous stroma, and the above IHC features) were analysed with a next‐generation sequencing panel of 324 cancer‐associated genes from formalin‐fixed, paraffin‐embedded tissue. All tumours harboured at least one alteration in either TSC1 (n = 7, 41%), TSC2 (n = 2, 12%), MTOR (n = 5, 29%) or PIK3CA (n = 4, 24%). Four tumours harboured a second alteration, including two NF2, one each in conjunction with MTOR and TSC2 alterations, one PTEN with TSC1 alteration and one tumour with both MTOR and TSC1 alterations. No other renal cancer‐related or recurring gene alterations were identified. In addition to the previously described IHC findings, 16 of 16 were positive for GATA3. Eleven patients with follow‐up had no metastases or recurrent tumours. Recurrent tuberous sclerosis/MTOR pathway gene alterations in LOT support its consideration as a distinct morphological, immunohistochemical and genetic entity. PIK3CA is another pathway member that may be altered in these tumours. Further study will be necessary to determine whether tumour behaviour or syndromic associations differ from those of oncocytoma and chromophobe carcinoma, warranting different clinical consideration. [ABSTRACT FROM AUTHOR]

Objectives: Solitary fibrous tumor (SFT) is a mesenchymal neoplasm that can arise at various anatomic locations. It is characterized by inv12(q13q13)-derived NAB2::STAT6 fusion, resulting in the nuclear expression of STAT6. Primary SFT of the adrenal gland is rare. We launched a multi-institutional collaboration to comprehend the overarching demographics, clinical and follow-up, macroscopic, microscopic, IHC, and FISH features of 9 patients with SFT of the adrenal gland.Methods: We added a series of 9 patients to the collection of adrenal SFTs where the clinicopathologic parameters, including clinical presentation, imaging, histopathology, IHC, molecular profiles, and management and follow-up data, were analyzed comprehensively. A modified 4-variable risk stratification model, including age, tumor size, and necrosis, was applied.Results: Our series consisted of 6 male and 3 female patients, ranging in age from 19 to 64 years (mean, 49.3 years). Abdominal pain (4) and fever with abdominal pain (1) were the presenting symptoms in 5 patients. In the remaining 4 patients, the tumors were detected by abdominal imaging for hypertension and diabetes. The size of the tumor ranged from 2 cm to 10.5 cm in maximum dimension. All tumors exhibited the morphology of a spindle cell SFT with a patternless architecture; 3 had a focal storiform arrangement. STAT6 positivity was observed in all tumors, and 7 were positive for CD34. Surgical resection was the primary modality of treatment. No adjuvant therapy was administered. Follow-up ranging from 7 months to 23 months was available for 7 patients. All were alive without disease recurrence or metastasis. Risk stratification placed 8 (88.9%) patients into a low-risk category and 1 into an intermediate-risk category.Conclusions: This series is the largest of adrenal SFTs to date. These tumors of the adrenal gland are predominantly spindle cell neoplasms with indolent behavior, with a wide age distribution and a slight male preponderance. Combining our cohort with the previously published cases, the majority of tumors fall into the low-risk category for the propensity to develop metastases. Owing to the rarity and age distribution associated with these tumors, the differential diagnosis is wide and requires a systematic approach for ruling out key differential diagnoses aided by STAT6 IHC. [ABSTRACT FROM AUTHOR]

Background: Choroid plexus carcinoma (CPC) is a predominately pediatric CNS tumor with a variety of histologic features, with hyaline globules only reported once previously. Case report: A two-year-old male child presented with headaches, vomiting, and lower limb weakness. Radiological examination revealed a right temporoparietal intra-axial tumor. On histology, it showed features of CPC containing multiple eosinophilic intracytoplasmic and extracellular hyaline globular structures, which were PAS-positive, diastase resistant, and immunoreactive for alpha-fetoprotein (AFP). Conclusion: CPC can occasionally show AFP immune-positive hyaline globules. [ABSTRACT FROM AUTHOR]

Background: A five-tiered reporting system for effusion fluid cytology has been published by the Indian Academy of Cytologists (IAC). Only a single study has evaluated the applicability of this system in routine reporting. Aims: We intend to evaluate the practical utility of this system in routine reporting of ascitic fluid cytology. Materials And Methods: Nine hundred and sixty-one cases of ascitic fluid cytology were included in this study. The clinical, radiological, cytomorphological, and follow-up data of these cases were reviewed. All cases were recategorized according to the proposed IAC system, and the risk of malignancy (ROM) for each category was estimated. Results: Age of the patients ranged from 1 to 92 years, and fluid volume ranged from 10 ml to 3 l. The number of cases included in each category and their respective ROM were as follows: category 1: 41, 21.42%; category 2: 805, 14.9%; category 3: 5, 33.3%; category 4: 31, 90%; and category 5:79, 96.4%. Conclusions: The new IAC guidelines for the serous fluid is representative, informative, and could be easily applied at our institutional level. We used the recommended diagnostic categories for reclassifying the ascitic fluid samples based on their cytosmear findings and conclude that the system has enormous utility at each level starting from the collection of fluid samples till the delivery of the report. [ABSTRACT FROM AUTHOR]

Phyllodes tumor is a paradigm of fibroepithelial neoplasm that accounts for <1% of the breast neoplastic lesions usually detected in females and uncommonly in the male breast. The World Health Organization classifies the tumor into benign, borderline, and malignant based on the predefined morphological criteria. Squamous differentiation in phyllodes tumor is epithelial metaplasia, which has been occasionally documented in English literature. We report the first undocumented case of a recurrent borderline phyllodes tumor with cystic squamous metaplastic change in a 32-year-old male patient. The histology was that of a fibroepithelial neoplasm with the typical leaf-like projections and cystic spaces lined by squamous epithelium containing keratin debris. The purpose of presenting this case is to elucidate the pathogenesis and discuss other malignant and benign breast lesions that may be included in the differential diagnosis when evaluating a breast lesion with squamous metaplasia, particularly in the context of fine-needle aspirates. [ABSTRACT FROM AUTHOR]

Osteoid osteoma (OO) affecting the spine is one of the common causes of painful scoliosis in the growing age group. The involvement is usually in the posterior elements involving the lumbar and cervical spine. We report a case of OO affecting the body of the thoracic vertebral body. A 15‑year‑old male presented with painful left thoracolumbar scoliosis. Computed tomography (CT) and magnetic resonance imaging (MRI) and MRI showed a lucent area with central dense focus (nidus) suggesting OO. Surgical excision was done under image intensifier and void filled with a mesh cage having bone graft reinforced posteriorly with pedicle screws. Postoperatively, the patient was relieved of his diffuse pain and CT scan revealed complete excision of the lesion . At the follow‑up, the patient has an active, unconstrained life. OO in the spine presents as scoliosis which can be painful or painless. The diagnosis can be missed on a plain radiograph and complete radiographic evaluation includes a CT scan and MRI. Spinal management includes curettage or radiofrequency ablation. Recurrence is a known but rare complication. [ABSTRACT FROM AUTHOR]

Urothelial carcinoma with villoglandular differentiation (UCVGD) is a rare aggressive variant of urothelial carcinoma. It is usually associated with high-grade urothelial carcinoma or rarely adenocarcinoma. There is only one other previous report of UCVGD associated with small cell neuroendocrine carcinoma of urinary bladder. We report the second case of UCVGD with small cell neuroendocrine carcinoma of urinary bladder in a 74-year-old non-smoker male patient. The mass was muscle invasive and also invaded the prostate. This entity needs to be confidently diagnosed due to its prognostic and therapeutic implications. [ABSTRACT FROM AUTHOR]

Benign tumours of the tonsils are rare. Majority of these lesions are diagnosed as squamous papilloma. Hamartoma is a benign tumor-like malformation. Hamartoma in tonsils is unique and only a few anecdotal cases are reported until now. Tonsillar hamartoma usually presents as unilateral or bilateral polyp with clinical features of dysphagia or foreign body sensation. Histopathologically, normal tissues are noted in a haphazard or disorganised way. We hereby present a case of 31-year-old male patient with tonsillar hamartomatous polyp presenting with the symptom of a foreign body sensation in the throat. The diagnosis of this entity and its distinction from other clinico-pathological mimickers require histopathological examination and awareness. A complete surgical excision is curative without any evidence of disease recurrence. [ABSTRACT FROM AUTHOR]