Renal Cell Carcinoma With Rhabdoid and Sarcomatoid Features Presented as a Metastatic Thigh Mass With an Unusual Immunohistochemical Profile
Male patient 70 years old presented with a thigh mass measured 35×24×9 cm with grayish white lobulated cut section. Histopathological examination revealed epithelioid sheets of cells exhibiting great pleomorphism and frequent mitoses (). Most of these malignant cells showed abundant eosinophilic cytoplasm with occasional eccentric nuclei (, ). Some areas showed clear cell changes (). Malignant multinucleated giant cells and areas of necrosis were also seen. The possibility for sarcoma was highly thought.\nImmunohistochemical panel of soft tissue sarcoma was performed including SMA, desmin, vimentin, S100 and pan cytokeratin. The neoplastic cells showed positivity for desmin () and vimentin and the mass was designated at that time as pleomorphic rhabdomyosarcoma. At this moment, the patient has not submitted to further investigations. The patient received 33 cycles of radiotherapy, during which, he suffered from bad wound healing of the thigh wound.\nUnfortunately, the patient suffered seven months later from abdominal pain. Abdominal CT revealed huge intra-abdominal mass that was located pararenal and extended to psoas muscle replacing and destroying it and both kidneys were free.\nThe patient underwent abdominal exploration where the intra-abdominal mass was resected. The mass measured 30×24×10 cm with whitish lobulated cut section (, ).\nMicroscopic evaluation of the abdominal mass revealed malignant epithelial cells characterized by clear cytoplasm with variable degrees of pleomorphism, where there were areas of moderate pleomorphiam to anaplastic areas (). The first impression of this mass is RCC versus adrenocortical carcinoma.\nStepping sections revealed areas simulating the morphology of thigh mass. Three iliac lymph nodes were dissected and revealed infiltration by the same neoplasm (). The tumor cells were diffusely positive for CD10 () and vimentin and focally positive for pan cytokeratin () and EMA ().\nThe tumor cells were completely negative for inhibin and other sarcoma markers such as SMA, desmin, myogenin and S100. Therefore, the morphological and immunohistochemical pictures indicated the diagnosis of RCC. But investigations failed to prove the presence of any renal masses. Paraffin blocks of thigh mass were retrieved and were submitted to immunostaining for CD10, EMA, vimentin, pancytokeratin, desmin, myogenin and carbonic anhydrase IX.\nFor our surprise, the tumor cells of thigh mass were diffusely positive for CD10 (), and vimentin and focally positive for pan cytokeratin (), EMA () and carbonic anhydrase () and still showed immunoreactivity for desmin. However, the tumor cells of thigh mass were negative for myogenin.\nTherefore, we are now dealing with the same tumor which is RCC metastasizing to the thigh. Patient died within two months after the resection of intra-abdominal mass and receiving one cycle of Doxorubicin.