Malignant epithelial-stromal renal tumor: Progressive atypical features in a case of male patient with fatal outcome

Abstract

Mixed epithelial-stromal tumors of kidney are rare neoplasm usually described in postmenopausal females under estrogenic therapy. Although tumor behavior is in general benign, sporadic cases with an aggressive behavior have been described. The present case is a 41-year-old male with lumbar pain, hematuria and lump in left kidney. Tumor spread assessment evidenced no findings and therefore radical nephrectomy was performed. Grossly tumor was peripherally located, whitish, round-shaped, measuring 9 cm. It showed spread to the pyelocalyceal system and necrotic areas. Histologically consisted of biphasic neoplasm, with epithelial component of branching ducts that covered a moderately cellular and partly spindle-cell stroma, with focal areas of marked atypia and prominent mitotic activity. Immunostains were positive for Pancytokeratin and Keratin 7 in the epithelial component, positive for Vimentin in both epithelial and stromal components, and positive for Actin only in isolated stromal cells. Immunostains were negative for Estrogen and Progesterone Receptors and CD99. Ki-67 was positive in 60% of pleomorphic stromal areas, in 20% of low-grade stromal areas and in < 5% of the epithelial component. Disease progressed in a few months with bilateral lung metastases and death. The present case is reported by to be a very rare case with malignant behavior and fatal outcome in a male patient. The aim of the present work is to contribute to the knowledge and characterization of such lesions.