[Clinicopathological features and prognosis of renal cell carcinoma with sarcomatoid differentiation]

To study the clinicopathological features and prognosis of renal cell carcinoma with sarcomatoid differentiation (RCCS).

The clinical data and pathological materials of 18 RCCS cases were retrospectively reviewed.The follow up data were available in 13 RCCS cases, and were compared with the follow up data of 20 cases of clear cell renal cell carcinoma (RCC).

The 18 RCCS patients included 14 males and 4 females, and were 49-79 years old (mean age: 62 years old). On gross examination, the tumor size was 3-19 cm in diameter (mean diameter: 9.8 cm). Histologically, all tumors were composed of a mixture of typical RCC with sarcomatoid component, including 9 clear cell RCC, 3 chromophobe RCC and one papillary RCC. The sarcomatoid components included 9 cases of fibrosarcoma, 3 cases of leiomyosarcoma, 5 cases of malignant fibrous histocytoma and one case of undifferentiated sarcoma. Immunohistochemistry showed that the sarcomatoid components were strongly vimentin-positive in 18 cases, and one or more epithelial markers (EMA, AE1/AE3, CK7, CK18) were expressed to varying degrees in 14 cases, but the high-molecular weight keratin 34βE12 was scarcely expressed. The sarcomatoid components presented positive expressions of CAIX in 88.9% (16/18) and CD10 in 72.2% (13/18) cases. Among the 18 RCCS patients, 13 patients were followed-up: 9 patients died in 1-25 months after the surgery, of which 5 cases died of lung or bone metastasis, and 4 patients died of systemic failure. The twenty RCC cases without sarcomatoid differentiation were followed up for 3-65 months after the surgery, and the majority of them was alive uneventfully except for 2 cases who died of lung or bone metastasis of the tumor. The Kaplan-Meier survival analysis showed that the median survival time of the 18 RCCS patients was 8 months, while that of the 20 RCC cases without sarcomatoid differentiation was 62 months (P<0.001).

The presence of sarcomatoid differentiation in renal cell carcinoma indicates highly aggressive behavior and poor prognosis. The positive expressions of the immune markers CAIX and CD10 may play important roles in the transformation from renal cell carcinoma to sarcomatoid component.