Dedifferentiated Liposarcoma of the Kidney: Surgical Management and Diagnostic Insights

This report presents the case of a 62-year-old male who presented with a two-month history of right flank pain and decreased appetite. Clinical evaluation revealed a palpable, non-tender mass in the right flank, while laboratory tests demonstrated mild anemia (hemoglobin 9.3 g/dL) with otherwise normal renal function. Contrast-enhanced computed tomography of the abdomen showed a large, heterogeneous mass arising from the lower pole of the right kidney, containing mixed densities, fatty components, and coarse calcifications. The initial differential diagnosis included angiomyolipoma. Following multidisciplinary discussion, the patient underwent radical nephrectomy. Gross examination revealed a lobulated, yellowish tumor with areas of necrosis and hemorrhage. Histopathological analysis confirmed the diagnosis of dedifferentiated liposarcoma, characterized by spindle cell proliferation with moderate nuclear atypia and mature adipocytes. Immunohistochemistry showed strong nuclear positivity for MDM2 and p16, supporting the diagnosis. The tumor was staged as pT3aNxM0. Postoperative follow-up was arranged to monitor for recurrence. This case highlights the diagnostic challenge posed by rare renal tumors with fatty components and emphasizes the importance of including dedifferentiated liposarcoma in the differential diagnosis. Early surgical intervention remains essential to optimize outcomes, given the tumor's limited response to adjuvant therapies.