OBJECTIVETo investigate the morphologic features and diagnostic criteria of various types pf renal adenomas of the kidney.

METHODSIn addition to light microscopy, electron microscopy, histochemical and immunohistochemical assays were applied. All 19 cases of adenomas were followed up.

RESULTSThree (3) cases of papillary adenoma were featured as papillary or tubulopapillary growth in patterns consisting of tumor cells with basophilic or acidophilic cytoplasm and were positive for both epithelial membrane antigen (EMA) and cytokeratin (CK7). Thirteen (13) cases of oncocytoma were characterized by the diversity of the structures including to be nest, tubular and papillary in pattern; a mixture of cell types including the classic oncocytes, oncoblasts and clear cells which were negative for vimentin and CK7 but positive for EMA. Enormous large mitochondria were obtained in 4 cases of oncocytoma by electronic microscopy. Three (3) cases of metanephric adenoma consisted of closely packed, round tubules lined by small bland cells with solid, glomeruloid constructure. Branching, elongated tubules and polypoid fronds were also detected. Tumor cells were negative for EMA, negative or only focally positive for CK7. Eighteen (18) patients were alive except one oncocytoma patient died 5 years after the diagnosis convinced. All the cases reported in this article had been followed up of 3 - 5 years.

CONCLUSIONSThere are 3 kinds of renal adenomas, namely, the papillary adenoma, oncocytoma, and metanephric adenoma and each kind has its own clincopathological features. The latter two can be recognized by their distinctive morphology, and the former can only be diagnosed according to the size of the tumor as the reference. Histochemical and immohistochemical assays are helpful in differential diagnosis.