We describe the imprint cytologic findings of primary renal angiomyolipoma, incidentally found in an autopsy case, presenting many bizarre neoplastic cells. Post-mortem examination of an 83-year-old Japanese woman revealed intestinal obstruction due to transverse colon cancer, and a right renal tumor measuring 1 cm. The imprint materials obtained from the renal tumor showed a mixture of four kinds of cells as follows: 1) scattered bizarre smooth muscle cells, 2) typical spindle-shaped cells, 3) mature adipose cells, and 4) endothelial cells of benign capillaries. This case suggests that cytopathologists should be alert to the existence of these hamartomatous neoplasms.
