Immunoexpression of SDHB, FH, and CK20 among eosinophilic renal tumors: A tissue microarray study

Eosinophilic solid and cystic renal cell carcinoma and renal cell carcinomas with TFEB alterations: a comparative study

AIMS

Eosinophilic solid and cystic renal cell carcinoma (ESC RCC) is a recently described renal tumour entity with frequent CK20 positivity, commonly harbouring TSC mutations. In contrast, frequency of CK20 expression and presence of TSC mutations are unclear in TFEB-amplified RCC and TFEB-translocated RCC, which frequently express Melan A. Herein, we provide a comparative analysis of 6 ESC RCC with 4 TFEB-amplified/translocated RCC.

METHODS AND RESULTS

We assessed the frequency of CK20 and Melan A expression by immunohistochemistry, and of TSC mutations by next generation sequencing. TFEB alterations were confirmed by fluorescence in situ hybridization (FISH). All tumours showed voluminous eosinophilic cells with granular cytoplasm, prominent nucleoli, and most showed admixture of solid and cystic areas. CK20 expression was found in all 6 ESC RCC and in all RCCs with TFEB alterations. Melan A positivity was identified in 5/6 ESC RCC and 4/4 RCC with TFEB alterations. We found TSC mutations in 2 ESC RCCs, including in one case also harbouring a CIC fusion, and identified a TSC mutation in one TFEB-amplified RCC.

CONCLUSIONS

ESC RCC represents an emerging renal tumour entity with some histological, immunohistochemical and molecular overlap to TFEB-amplified/translocated RCC. FISH for TFEB aids in this differential diagnosis in challenging cases.

Low-grade oncocytic tumor of kidney harboring TSC/MTOR mutation: clinicopathologic, immunohistochemical and molecular characteristics support a distinct entity

Low-grade oncocytic tumor (LOT) has recently been described as a distinct renal tumor. LOT shows consistent morphologic features and a CK7-positive/CD117-negative immunophenotype. To examine the clinicopathological, immunohistochemical, and molecular features of LOT, we searched our institutional archives and identified seven cases of LOT. All patients were female, with a mean age of 66 years (range 44-79 years). The average tumor size was 3.2 cm (range 1.6-5.5 cm). Macroscopically, the tumors showed tan-brown and solid cut surfaces. Microscopically, the tumors showed compact nested to solid growth pattern, three cases with areas of edematous stroma containing loosely connected small clusters, cords or dispersed single tumor cells. The tumor cells had uniformly round to oval nuclei with eosinophilic cytoplasm, and showed perinuclear halos. Two cases focally had nuclear irregularities and binucleated cells were occasionally seen in three cases. Immunohistochemically, diffuse positivity for CK7 and lack of CD117 expression were present in all cases. All of the tumors were negative for CD10, CK20, vimentin, CA9, TFE3, TFEB, HMB45, and Melan-A. All tumors were positive for MTOR and negative for Cathepsin-K. FH and SDHB were retained. Next generation sequencing identified genetic variations in the MTOR pathway related genes: TSC1 (4/7), TSC2 (5/7), and MTOR (1/7). All patients were alive and without disease progression, after a mean follow-up of 43 months (range 6-89 months). LOT is an uncommon eosinophilic renal neoplasm with unique morphological and characteristic immunophenotypic features, and may represent an emerging separate renal entity characterized by mutations in the TSC/MTOR pathway.

Diagnostic accuracy of core biopsies of renal masses: Experience in a real-life setting from a tertiary center

OBJECTIVE

To document and analyze diagnostic accuracy of renal core biopsy (RCB), its diagnostic correlation with resection specimens, and to question the need for immunohistochemistry (IHC) in the preoperative diagnosis of renal masses.

MATERIAL AND METHOD

RCBs performed at a reference center between 2007 and 2017 were included. Pathological, clinical, and radiological data were obtained from medical records.

RESULTS

Among 302 biopsies included in this study, 274 (90.7%) were diagnostic. Two hundred sixty-six were neoplastic and 179 were of primary renal origin. The most common secondary neoplasms were hematolymphoid (n = 35) and metastatic (n = 17). Sixty-nine tumors were classified as small renal masses (SRMs) (≤4 cm in diameter) and 53 of them were malignant. Nephrectomy was performed in 58 patients. Overall diagnostic accuracy between resections and RCBs was 88.7%. IHC was performed in 160 (53%) cases. In 15 of those, a definite diagnosis could not be rendered. Renal cell origin and subtype were determined by histomorphology alone in 81 and 75 cases, respectively. Sixty primary neoplasms of renal cell origin required IHC for diagnosis.

CONCLUSION

RCB is a safe and highly accurate method for the diagnosis of both primary and secondary renal neoplasms. IHC is mostly required for the diagnosis of secondary tumors. Histomorphology is still the primary diagnostic tool, highly dependent on the experience of the surgical pathologist.