Renal oncocytosis - A morphologic study of fourteen cases

Diffuse renal involvement by numerous oncocytic nodules has rarely been des cribed. We report 14 cases (19 specimens) with innumerable oncocytic nodule s in the kidney. Invariably, these kidneys showed additional associated fin dings. We suggest the term renal oncocytosis for this entire morphologic sp ectrum. Six (43%) cases had histologically or radiologically proven bilater al involvement. Each specimen had at least one dominant tumor (2.0-10.5 cm) in addition to numerous other microscopic to macroscopic oncocytic nodules . Additional features observed were: interstitial pattern, with the oncocyt ic tubules and acini diffusely intermingling with and infiltrating between nonneoplastic parenchyma (one case); diffuse oncocytic change in the nonneo plastic tubules, cytologically difficult to separate from the oncocytic nod ules (seven cases); and benign oncocytic cortical cysts (four cases). The d ominant mass in 13 specimens was a renal oncocytoma and in two, a chromopho be renal cell carcinoma. In four specimens, the largest tumor was considere d a hybrid tumor because of the presence of mixed histologic features of bo th tumor types. Most smaller nodules had the morphologic features of renal oncocytoma, but a few had the appearance of chromophobe renal cell carcinom a or nodules with hybrid features. We conclude that the presence of numerou s oncocytic nodules may be associated with a wide spectrum of oncocytic cha nges in the kidney. The association of numerous renal oncocytoma-like nodul es with lesions having a mixed morphology or a morphology of pure chromopho be renal cell carcinoma suggests that they may constitute a morphologic spe ctrum of oncocytic tumors and that renal oncocytoma and chromophobe renal c ell carcinoma may arise from a common progenitor lesion.