Renal Leiomyosarcoma: Unraveling the Mysteries of a Rare Malignancy.

Primary leiomyosarcoma is a rare malignant kidney tumor. The diagnosis of this disease is usually made on the basis of histological examination because it lacks specific clinical or radiological characteristics. Differentiation between leiomyosarcoma and sarcomatoid renal cell carcinoma can be challenging because spindle cell morphology is observed in both tumors. Therefore, caution should be exercised when making a diagnosis of primary renal leiomyosarcoma. Both renal sarcoma and sarcomatoid renal cell carcinoma have a worse prognosis, and nephrectomy is the treatment of choice in locally resectable tumors. An example of such a tumor is discussed in relation to its diagnostic challenges. We report a case of a 35-year-old female who presented with a left renal mass. A left radical nephrectomy was performed, and a firm, tan-white, lobulated tumor (14x8x7.5 cm) was present on gross examination. A histological diagnosis of high-grade leiomyosarcoma was made on the basis of histology, positivity for caldesmon and desmin, and negative cytokeratin immunostaining. Sarcomatoid renal cell carcinoma was ruled out based on morphological findings after extensive sampling of the tumor along with negativity for CK, CD-10, and carbonic anhydrase IX immunostaining.