Details
Renal mass.
Renal oncocytoma is a benign, well circumscribed, oncocytic neoplasm with characteristic round cells that have oncocytic cytoplasm and uniform nuclei with evenly distributed cytoplasm and prominent nucleoli. The architecture of renal oncocytomas can be in solid nests, cystic and tubulocystic, the latter can mimic tubulocystic carcinoma; the benign nuclear features of renal oncocytoma help to differentiate these two entities. Familial syndromes have been described, rarely, including Birt-Hogg-Dubé syndrome.
Immunohistochemistry can be helpful as an ancillary technique to morphology in differentiating renal oncocytoma from malignant entities on the differential diagnosis such as eosinophilic chromophobe renal cell carcinoma. Immunophenotype is positive for CD117, E-cadherin, Ksp-cadherin, S100-A, CK-PAN, and low molecular weight cytokeratins; CK7 is negative or scattered, focally positive cells; and negative for vimentin.
References:
1) Mills, Stacey E. Sternberg's Diagnostic Surgical Pathology. 5th Edition, 2010, p. 1774