Abstract: Abstract: Objective To study the clinicopathological features and immunophenotype of primary rhabdomyosarcoma of the kidney. Methods 2 cases of primary rhabdomyosarcoma of the kidney were collected from 2000 to 2009 in the second hospital of Tianjin medical university.The immunohistochemical SP method was used to detect the expression of Vimentin、Myoglobin、Desmin、α-SMA、EMA、NSE、S-100.The clinical findings were analyzed and the hematoxylin and eosin-stained sections were reviewed. Results Primary rhabdomyosarcoma of the kidney account for 0.2% of malignant renal tumors. Both of the patients were male.One tumor was on the left and one on the right.The tumors with moderate pleomorphism composed of alternating fascicles of spindle cells with blunt-ended nuclei and eosinophilic cytoplasm.After SP staining, Vimentin showed positive or strong positive expression, but Myoglobin, Desmin was negative, EMA, NSEand S-100 expression in various degrees. Conclusion Primary leiomyosarcoma of the kidney is a rare malignant tumor of the kidney.Diagnosis of this tumor need to be differentiated from diverse malignant renal tumors by pathohistology、histochemical stain and immunohistochemical stain.

Key words: Kidney neoplasms, rhabdomyosarcoma, Pathology, Histologic appearance, Immunohistochemistry