楊旻鑫¹, 王紹全¹, 李祥麟²

¹中山醫學大學附設醫院 泌尿科

Ming-Hsin Yang¹,

¹Department of Urology, Chung Shan Medical University Hospital, Taichung, Taiwan

²Department of Surgery, Chung Shan Medical University Hospital, Taichung, Taiwan

 

Metanephric adenoma (MA) is an extremely rare benign neoplasm of the kidney that accounting for 0.2% of adult renal epithelial neoplasms, with only less than 200 cases worldwide. The mean age of patients with MAs is 41.

Here, we presented a case of 71 years old man with palpable abdominal mass for 4 years. Computed tomography of abdomen revealed a huge, heterogeneous mass measured 31×18 cm in size containing calcification and arising from the right retroperitoneal space. (Figure 1A, 1B) Surgery was done with midline incision of abdomen. After exposure the retroperitoneal tumor from lateral side of ascending colon, the mass originates from low pole of right kidney was noted. The tumor was removed after ligating the supplying vessel and radical nephrectomy was then performed. (Figure 1C) The pathological examination showed MA composed of tightly packed small acini lined by uniform small cells with inconspicuous cytoplasm. The nuclei are uniform, ovoid and have inconspicuous nucleoli. In addition, immunohistochemical staining showed reactive for CD57 and Vimentin, and negative for CK7, RCC, WT-1, EMA, AMACR. The proliferative index of Ki-67 is < 1%. Papillary renal cell carcinoma (PRCC) and epithelial Wilm’s tumor which have mimic histological features may thus rule out. This patient was free from recurrence after a follow-up period of 2 years.

Due to the limited amount of MA, the features of biological, imaging, and pathological have not been clearly described. Furthermore, this case might be the biggest MA in the literature. He received laparotomy radical nephrectomy with excellent outcome. Our report may increase in the familiarity of this disease in the future.