Renal Leiomyosarcoma with Mixoid Component: Case Report and Literature Review

Primary leiomyosarcoma is an extremely rare entity constituting only 0.5–1% of all invasive renal tumors. It is frequently diagnosed after histological examination because it does not have any specific diagnostic features clinically and radiologically. At times, it is difficult to differentiate leiomyosarcoma from the sarcomatoid renal cell carcinoma even during histological examination as both tumors have spindle-shaped atypical cells. Moreover, some epithelial markers can be present in pure smooth muscle sarcomas, while some smooth muscle markers are positive in carcinomas. An extremely uncommon condition is leiomyosarcoma that develops in the renal pelvis. A patient with an obstructive stone-related left renal colic was admitted to hospital with a filling defect in the renal pelvis, which was initially misdiagnosed as a blood clot. After visual examination of the renal pelvis and a biopsy of the exophytic lesion, leiomyosarcoma was determined to be the cause. Laparoscopic radical nephrectomy was performed, histological and immunohistochemical examination confirmed the lesion to be a leiomyosarcoma with mixomatoid component. No adjuvant treatment was performed, and the patient remains healthy 6 years after surgery without recurrence. Herein we provide literature review, discussion of the diagnosis and treatment scenario of the patient with renal pelvis leiomyosarcoma with mixomatoid component.