12. Fine needle aspiration biopsy of renal mucinous tubular and spindle cell carcinoma: report of fine needle biopsy in conjunction with a core biopsy

Abstract

Renal mucinous tubular and spindle cell carcinoma is rare but with distinct and well described histopathological features. To our knowledge only six cases of fine needle aspiration have been described in the literature. The majority has a favourable prognosis and therefore it is important to distinguish this entity from other renal cell carcinomas. We report one case of renal mucinous tubular and spindle cell carcinoma. A CT scan for an evaluation of left-sided shoulder pain showed an incidental 45 mm right-sided renal lesion. The lesion was initially evaluated by two CT guided 22 G fine needle aspirations (FNAB) in conjunction with two 22 G core biopsies. The patient is now on the waiting list for a laparoscopic radical nephrectomy. The cytomorphological features of mucinous tubular and spindle cell carcinoma (MTSCC) were characterised by sheets and complex branching tubular structures with some background mucin. The cells showed round nuclei with little variability and no obvious mitoses. The findings of the core biopsy confirmed the diagnosis of a MTSCC. There were cords and tubules of epithelial cells with rounded, regular nuclei. There was loose mucinous background. Immunoperoxidase staining was positive for Vimentin, CK7, CK 18, CK19, 34 BE12 and EMA but negative for CD10. Findings of tubular structures with bland cells and mucinous background of a renal FNAB should include renal mucinous tubular and spindle cell carcinoma in the differential. With a few exceptions like sarcomatoid changes this tumour has a favourable diagnosis and therefore should be readily recognised on FNAB.