Mucinous tubular and spindle cell carcinoma of the kidney with aggressive behavior: An unusual renal epithelial neoplasm: A case report

Mucinous tubular and spindle cell carcinoma is a rare low-grade renal cell carcinoma, which was first described as a new entity in the World Health Organization 2004 classification. We report here on a case of this tumor with very unusual aggressive behavior. A 73-year-old man presented with gross hematuria. A computed tomography scan demonstrated a 5 cm sized low density mass in the left kidney. The radical nephrectomy specimen grossly showed a well demarcated tumor confined to the renal parenchyma. Histologically, the tumor consisted of elongated tubules or trabeculae of oval to cuboidal cells with a low nuclear grade, and these tubules/trabeculae were separated by abundant acidic mucinous stroma. In some areas, spindle cell components were mixed with parallel tubules. Neither significant atypia nor mitosis was seen. The patient developed multiple metastatic pulmonary nodules 2 months later. Four months after the surgery, the left supraclavicular, right hilar and right subcarinal lymph nodes were also enlarged by metastasis. The patient died of respiratory failure 13 months after the operation.