Revista de nefrología y terapéutica

A giant mixed epithalial and stromal tumor (Adult Mesoblastic Nephroma) mimicking intraparenchymal leiomyoma of the kidney- Zafer Demirer- Eskisehir Military Hospital

Abstract

Zafer Demirer

Background & Aims: Adult’s kidneys tumor classification expands rapidly with new categories which are including recently being incorporated tumors also. Mixed epithelial stromal tumor of the kidney (MESTs) was recently described and unusual entity. This rare complex renal neoplasm composed of a mixture of cystic and solid components. Although mesoblastic nephroma mostly detected in during the first few weeks of life, the first case of adult mesoblastic nephroma which was grossly and microscopically similar to congenital mesoblastic nephroma was described in 1973. These tumors also termed as benign mixed epithelial and stromal tumor (MESTs) by Michal and Syrucek in 1998. Since then, it has been reported with different names which are leiomiyomatous renal hamartoma, adult type congenital mesoblastic nephroma, adult metanephric stromal tumor, cystic hamartoma of renal pelvis, solitary multilocular cysts of the kidney and multilocular renal cyst with mullerian-like stroma. Herein, we report unusual tumor of the kidney which abundant stroma and devoid of epithelial component. Patient & Methods: A 22-year old female presented with a palpable right-sided abdominal mass and microscopic hematuria. She had no history of hypertension and all laboratory values were normal. A 15 cm heterogenous solid, right renal mass which was displacing the renal parenchyma revealed by contrast-enhanced CT scan without adenopathies Renal mass was also confirmed by MR imaging and there was marked displacement of the inferior vena cava without tumoral infiltration. Results: We performed open right radical nephrectomy. Gross examination revealed a large, tan-gray solid mass, compressing the adjacent renal parenchyma. On the cut surface, an encapsulated tan-gray renal mass with 14x13x12 cm in dimension was detected. There was no any cystic change and it had completely solid appearance. Microscopic examination revealed a well-circumscribed mesenchymal tumor consisting of mostly intersecting fascicles of spindle cells with abundant intercellular collagen. The lesion also focally consisted of hypocellular areas with myxoid changes. The lesion was devoid of epithelial component and tubule or gland like epithelial structures within the Müllerian stroma at periphery of the tumor. The final pathologic diagnosis was adult mesoblastic nephroma with no atypical features. Convalescence was uneventful and she was discharged 4th day of the surgery. The patient was free of disease on the 18-months follow-up examination. Conclusions: (MEST) is a rare neoplasm of the kidney. 25% of the subjects were detected incidentally and they consist 0.20 to 0.28 percent of renal tumors. The main differential diagnosis of (MEST) is renal cell carcinoma. For accurate diagnosis, histopathologic examination is a gold standard.