Chromophobe renal cell carcinoma with osseous metaplasia: a case report.

A 60-year-old Japanese male with a chromophobe cell carcinoma of his left kidney is reported. The tumor, 18 x 27 mm in size, was incidentally found by abdominal ultrasonography. Computed tomography and magnetic resonance imaging demonstrated a well-demarcated solid tumor arising from the lower pole of the left kidney. Histopathological examination of the surgically removed tumor revealed that it was composed of solid sheets of cancer cells having abundant and slightly eosinophilic reticular cytoplasm with accentuated cell membranes making up a plant cell-like appearance. Electron microscopic examination demonstrated numerous intracytoplasmic microvesicles. Although the tumor cells were positive for cytokeratin and epithelial membrane antigen, they did not show vimentin immunoreactivity. The unique histological finding of this tumor from other reported renal chromophobe carcinomas was that it had a peripheral fibrotic area with a focus of metaplastic ossification.