OBJECTIVETo investigate the clinical and pathological features of the mucinous tubular and spindle cell carcinoma (MTSCC) of the kidney.

METHODSSeven cases of MTSCC were analyzed by gross examination and light microscopy. Immunostaining was performed to detect the expression of CD10, CK7, CK18, CK19, Villin, EMA, P504S and vimentin. The literature on this tumor was reviewed to discuss the histological features of MTSCC and its clinical behavior.

RESULTSThree of 7 cases were male and the other 4 were female. The mean age of the patients was 48.2 years old, with a range from 39 to 61 years. All the patients presented no symptom and their tumors were found by health examination. Tumors averaged 5.5 cm in greatest dimension (range from 4.0 cm to 9.0 cm). The tumors were well-circumscribed without capsules, and the cut surfaces were solid and soft with white-tan color. By light microscopy, tumors were composed of tightly packed, small, elongated tubules with transitions to spindle cell components. Five cases had mucinous stroma. Clear cell clusters, focal sarcomatoid differentiation, papillations and foamy macrophages were seen in several cases. Immunohistochemically, all 7 cases showed positive for CK7, five of 5 cases positive for EMA, CK18 and P504S, four of 5 cases positive for CK19, but heterogeneous for CD10, villin and vimentin expression. No evidence of local recurrence or distant metastases was identified in the 5 patients with follow-up information.

CONCLUSIONSThe mucinous tubular and spindle cell carcinoma is a low-grade and polymorphic neoplasm. The morphology of these tumors may not be uniform with a wide histological spectrum. The tumors can be tubular predominant or spindle cells predominant with scant to abundant mucinous stroma, which coupled with the presence of other unusual features such as clear cells, papillations, foamy macrophages, necrosis and sarcomatoid differentiation. Immunohistochemically, MTSCC can express the markers from the proximal convoluted tubules to collecting tubules.