Primary oat cell carcinoma of the kidney.

A malignant renal neoplasm with all the morphologic attributes of oat cell (small cell, neuroendocrine) carcinoma is presented. It metastasized widely to regional lymph nodes and resulted in the death of the patient. Ultrastructurally, the tumor contained dense-core endocrine-type secretory granules. It had a cell component which was argyrophilic and which gave a positive immunocytochemical reaction for calcitonin. To the best of our knowledge, this is the first documentation of this tumor type in the kidney.