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Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare subtype of RCC classified as a molecularly defined RCC in the fifth edition of the WHO. Most gene alterations in patients with SDH-deficient RCC involve the SDHB subunit, with less involvement of the SDHC, SDHA, and SDHD subunits. Four cases of SDHA-deficient RCC have been reported in the literature, of which one case was associated with an NF2 gene mutation. Herein, we report six novel SDHA-deficient RCC cases, including two cases with NF2 gene mutations. In contrast to the typical morphology of SDH-deficient RCC, the six tumors mainly displayed glandular, sheet-like, or papillary growth patterns with prominent nucleoli (Grades 2–3), among which two cases with NF2 mutations had prominent nucleoli (Grade 3), large transparent vacuoles in the cytoplasm, and a large number of lymphocytes in the stroma. Six tumors showed negative immunohistochemical staining for SDHA and SDHB, and three cases presented with high expression of PD-L1. Second-generation sequencing revealed novel pathogenic somatic SDHA gene mutation and NF2 gene mutations in six and two tumors, respectively. Follow-up data were collected for the six patients with a follow-up time ranging from 7 to 268 months, and all six patients have survived to date. One patient received targeted therapy for tumor metastasis to the lungs after seven months, and another patient with an NF2 gene mutation received immunotherapy for lymph node metastasis revealed during surgery. SDHA-deficient RCCs with NF2 gene mutations have the ability to metastasize but might respond well to immunotherapy. For the first time, we report the largest number of SDHA-deficient RCC cases and comprehensively investigate their clinicopathological and molecular features to provide important guidance for diagnosis and clinical immunotherapy. • SDHA-deficient RCCs displayed solid sheet, glandular or papillary growth distinct from typical SDH RCC. • SDHA-deficient RCCs with NF2 gene mutation presented pleomorphic nuclei, large vacuoles and high PD-L1 expression. • SDHA-deficient RCCs with NF2 gene mutation might exhibit unfavorable prognosis but good immunotherapy effect. [ABSTRACT FROM AUTHOR]

Aims Anaplastic lymphoma kinase ( ALK)-rearranged renal cell carcinoma ( RCC) is a rare subtype of RCC reported in recent years, with eight cases so far. The aims of the present study were to screen ALK-rearranged cases from a large cohort of RCCs in China to determine the frequency of ALK rearrangement and investigate the clinicopathological features and outcomes. Methods and results Tissues from a total of 477 RCC patients in China were embedded into tissue microarrays for immunostaining. Fluorescence in-situ hybridization ( FISH) and fluorescence quantitative reverse transcription polymerase chain reaction ( RT- PCR) were applied to identify and confirm the rearrangement of ALK, and to identify the genes fused with ALK. ALK expression was identified in two of 477 RCCs. By FISH analysis, the two tumours showed either a 1R1G1F or a 2R2G signal pattern, indicating rearrangement involving ALK. Fluorescence quantitative RT- PCR detected the TPM3- ALK fusion and EML4- ALK fusion transcripts in the two tumours, respectively. Follow-up data were analyzed for the two cases and eight other ALK-rearranged RCCs reported in the literature. Two patients died from RCCs, on the 16th month and 48th month after surgery, respectively. The 5-year cancer-specific survival rate of patients with the 10 ALK-rearranged RCCs was lower than that of patients with International Society of Urological Pathology (ISUP) G1, G2 and G3 clear cell RCC ( CCRCC) and papillary RCC ( PRCC), but higher than that of patients with G4 CCRCC and PRCC. Conclusions ALK-rearranged RCC is a rare subtype of adult RCC and is associated with distinct histological features and a poor prognosis. Identification of ALK-rearranged RCC has important clinical significance, because patients might benefit from ALK inhibitor therapy as used in lung adenocarcinoma. [ABSTRACT FROM AUTHOR]

Background: Renal cell carcinoma (RCC) with sarcomatoid differentiation is a relatively rare tumor containing both carcinoma and sarcomatoid components. However, there has not been a systemic study on immunophenotypes of renal cell carcinoma with sarcomatoid differentiation, especially using some renal specific immunohistochemical markers. In this study, we aimed to comprehensively investigate the distinct immunophenotypes of RCC with sarcomatoid differentiation to analyze the pathogenesis of sarcomatoid differentiation and identify new prognostic factors in RCC with sarcomatoid differentiation.Methods: A total of 42 cases of RCCs with sarcomatoid differentiation were enrolled into the study. Immunohistochemistry study was performed on tissue microarrays to evaluate the expressions of 19 immunohistochemical markers including a series of epithelial, mesenchymal markers and RCC specific markers. Kaplan-Meier method was applied to assess the prognostic values of CD10, CAIX, p53 and Bcl-2.Results: Histologically, 42 cases of RCCs with sarcomatoid differentiation presented with different proportions of carcinoma and sarcomatoid components. The cohort contained 35 cases of clear cell renal cell carcinoma (CCRCC) and 7 cases of chromophobe renal cell carcinoma (ChRCC) based on the carcinoma components. Immunohistochemically, all cases were positive for vimentin, and 80% of cases showed immunostaining for at least one epithelial marker, such as CK, EMA, CK7 and CK18. Notably, the expression rates of CAIX, CD10 and PAX8 in sarcomatoid cells were 76%, 76% and 64%, respectively. The carcinoma component of the tumors showed differentient labeling for CAIX, CD10, vimentin, CK7 and CD117 in CCRCC vs ChRCC, but the sarcomatoid component lost the specificity for these markers ( p < 0.05). Patients with positive expressions of CAIX, p53 and Bcl-2 had a poor prognosis.Conclusions: The sarcomatoid cells in RCC with sarcomatoid differentiation express both epithelial and mesenchymal markers, supporting their epithelial origin. PAX8, CAIX and CD10 could be used as the reliable and useful markers to determine the renal origin of sarcomatoid cells such as in fine needle aspiration cases and metastatic RCC with sarcomatoid differentiation. CAIX, p53 and Bcl-2 might play important roles in the transformation from renal cell carcinoma to high malignant sarcomatoid differentiation, and these three immunohistochemical markers are adverse prognostic factors for the survival of patients with RCC with sarcomatoid differentiation. [ABSTRACT FROM AUTHOR]

Xp11.2 translocation/ TFE3 rearrangement-associated renal cell carcinoma (RCC) and Xp11 translocation renal mesenchymal tumor are distinct tumor entity. To broaden the spectrum of Xp11 neoplasms, we investigated a novel tumor exhibiting morphologies overlapping Xp11.2 translocation/ TFE3 rearrangement-associated RCC and the mesenchymal counterpart with melanocytic differentiation by immunohistochemistry, fluorescence in situ hybridization (FISH) and RNA sequencing, as well as literature review. Histologically, the tumor was composed of three different types of tumor cells, including a large proportion of clear cells, small round cells, and a few spindle cells, presenting a relatively clear border in the majority area. The nuclei of all tumor cells showed extensively and strong positive expressions of TFE3. Whereas, the clear cells positively expressed the RCC-related markers including PAX8, RCC marker and CD10, and negatively expressed HMB45; On the contrary, the small round cells and spindle cells positively expressed melanocytic marker HMB45, and negatively expressed PAX8, RCC marker and CD10. The ki67 index was higher in the small round cells and spindle cells than that in the clear cells. FISH revealed the rearrangement of TFE3 gene in all the three types of cells. The NONO-TFE3 fusion gene was detected in all tumor cells by RNA sequencing. This unique Xp11 translocation-associated neoplasm might represent a distinct entity overlapping Xp11 translocation RCC and the mesenchymal counterpart with melanocytic differentiation, broadening the spectrum of Xp11 neoplasms. The patient died of tumor recurrence and lung metastasis after seven months after the surgery suggesting those tumors have an unfavorable prognosis. [ABSTRACT FROM AUTHOR]

Abstract: Papillary renal cell carcinoma (PRCC) includes two different morphological subtypes. The differences of genetics and ultrastructure of the two subtypes have been rarely reported. Also, new biomarkers related to the diagnosis and prognosis of PRCC have still not been well elucidated. Immunohistochemistry, fluorescence in situ hybridization (FISH) and transmission electron microscopy were used systematically to determine the characteristics of 56 cases of PRCC and to reveal new diagnostic and prognostic information. Type 1 PRCC presented higher expression rates of EMA and CK7, whereas type 2 presented a higher expression rate of CD10. New immunohistochemical markers, including: p504s, PAX-2, PAX-8 and CA-IX showed extensive immunostaining in PRCC. We first revealed a distinct immunostaining pattern of CA-IX, which was located in multiple foci in PRCC. All tumors had at least one chromosomal aberration including loss of Y, gains of 7 or 17. Gain of chromosome 17 was common in type 1; losses of chromosome 18, 11 and 8 appeared in type 2. Ultrastructurally, glycogen granules and secondary lysosomes were seen in type 1, mitochondria and smooth endoplasmic reticulum were scattered in type 2. Tumor subtype, nuclear grade, TNM stage, clear cell renal cell carcinoma (CCRCC) component and sarcomatoid elements, metastasis, CAIX expression, losses of chromosome 18 and 8 were related to poor outcome of PRCC. We conclude that the two subtypes of PRCC originate from different renal cells, and arise from partially common genetic pathways. EMA, CK7, CD10, p504s, PAX-2, PAX-8 and CA-IX are helpful markers in the differential diagnosis of PRCC. CA-IX expression, losses of chromosome 18 and 8 are new prognostic factors of PRCC. [Copyright &y& Elsevier]