Mucinous tubular and spindle cell carcinoma of the kidney: cytopathologic findings

A 54-year-old woman was hospitalized for flank pain and acute renal failure when imaging studies revealed a 5.2 cm mass in the left kidney. She was referred for fine needle aspiration of the lesion, which showed an epithelial tumor with round to oval nuclei associated with strands of metachromatic stromal tissue. Cytopathologic diagnosis was consistent with renal cell carcinoma. Subsequent nephrectomy was performed and the surgical pathology specimen showed a mucinous tubular and spindle cell carcinoma of the kidney. The patient has done well post-operatively with 10 months of benign follow-up.