A Case of Low-Grade Oncocytic Tumor/Chromophobe Renal Cell Carcinoma (Oncocytic Variant) of the Kidney

The oncocytic variant of chromophobe renal cell carcinoma (oChRCC) and low-grade oncocytic tumor (LOT) is introduced as new renal disease entity. Both of these tumors are low-grade malignancies consisting of cells with eosinophilic cytoplasm. Distinguishing between eosinophilic variant of chromophobe renal cell carcinoma (eCRCC) and oncocytoma is often a diagnostic challenge in routine surgical pathology. However, oChRCC and LOT might be independent disease entities that might not fit completely into any of these categories. Histologically, these tumors have greater morphological similarity with oncocytoma than with ChRCC. However, immunohistochemically, they exhibit diffuse and dense positivity for CK7 and are negative for CD117. In the present case, we initially had difficulty distinguishing among oncocytoma, eCRCC, and type 2 papillary renal cell carcinoma (2-pRCC). However, after learning about new disease entities such as oChRCC and LOT, we were able to diagnose this tumor.

MORPHOLOGICAL FEATURES AND IMMUNOPHENOTYPIC ASPECTS OF HYBRID KIDNEY TUMOR

A hybrid oncocytic/chromophobic tumor or a low malignant oncocytic tumor is not officially included in the clas- sification of 2016 WHO kidney tumors, however, in the literature, some authors consider this tumor as an independent nosological unit. A number of authors describe a hybrid oncocytic / chromophobic tumor consisting exclusively of relatively small oxyphilic cells resembling both oncocytes and chromophobic renal carcinoma cells at the same time. The development of morphological and immunohistochemical criteria for a hybrid oncocytic / chromophobic tumor is an important link in the differential diagnosis of renal cell carcinomas with oncocytic morphology. The aim of the study is a comparative analysis of the morphological, histochemical, immunophenotypic parameters of oncocytoma, chromophobic renal cell carcinoma and hybrid oncocytic / chromophobic tumor. Materials and methods. The study was performed on operational material from 162 patients undergoing surgical treatment at the Urological Clinic I. M. Sechenov and the Urology Center of the Scientific Clinical Center (NCC) of Russian Railways for kidney oncocytoma and chromophobic renal cell carcinoma from 2011 to 2017. Immunohistochemical studies were performed on paraffin sections according to the standard protocol. Antibodies used: EABA, Caveolin-1, MOC31, CyclinD1, CD10, CD117, EpCAM, CK7, DOG1, CAM5.2, CK19, E-Cadherin, Parvalbumin, KSC, PAX2, PAX8, S100A1 and MUC-1. Results. Based on the performed morphological and immunohistochemical analysis of 162 tumors in 61 (38%) cases revealed oncocytoma, in 35 (22%) showed cases classical chromophobic renal cell carcinoma, in 59 (36%) samples eosinophilic chromophobic renal cell carcinoma and 7 (4%) cases had a hybrid oncocytic/ chromophobic tumor. Conclusion. In some cases, a hybrid oncocytic / chromophobic tumor can be represented exclusively from “hybrid” cells with borderline signs of oncocytoma and eosinophilic chromophobic renal cell carcinoma.

Adrenal Oncocytic Neoplasm with Paradoxical Loss of Important Mitochondrial Steroidogenic Protein: The 18 kDA Translocator Protein

The adrenal glands produce a variety of hormones that play a key role in the regulation of blood pressure, electrolyte homeostasis, metabolism, immune system suppression, and the body’s physiologic response to stress. Adrenal neoplasms can be asymptomatic or can overproduce certain hormones that lead to different clinical manifestations. Oncocytic adrenal neoplasms are infrequent tumors that arise from cells in the adrenal cortex and display a characteristic increase in the number of cytoplasmic mitochondria. Since the rate-limiting step in steroidogenesis includes the transport of cholesterol across the mitochondrial membranes, in part carried out by the 18-kDa translocator protein (TSPO), we assessed the expression of TSPO in a case of adrenal oncocytic neoplasm using residual adrenal gland of the patient as internal control. We observed a significant loss of TSPO immunofluorescence expression in the adrenal oncocytic tumor cells when compared to adjacent normal adrenal tissue. We further confirmed this finding by employing Western blot analysis to semiquantify TSPO expression in tumor and normal adrenal cells. Our findings could suggest a potential role of TSPO in the tumorigenesis of this case of adrenocortical oncocytic neoplasm.