[Clinical features analysis of metanephric adenoma: a series of 16 cases]

Objective: To study the clinical characteristics, image findings, therapeutic method and prognosis of metanephric adenoma. Method: The clinical characteristic, image findings, operation methods and prognosis of 16 metanephric adenoma patients treated at Department of Urology, Peking University First Hospital from January 2004 to March 2016 were analyzed retrospectively. Results: There were 6 male and 10 female patients in the study. The mean age of patients was 33.7 years (ranging from 14 to 83 years). Two patients came to the hospital because of fever, while other 14 patients had no symptoms and found renal tumor by medical examination. One case was found polythemia vera and another 1 case showed mild anemia. Serum creatine of all the cases were in normal range. The tumor of 11 cases were at left side and 5 cases were at right. All patients took urinary tract ultrasound. Fifteen patients took CT examination. Among them, 14 cases were solid mass and 1 case was cystosolid.CT value was (41±4) HU. CT scan showed that the tumor was slight enhanced and CT value increased to (77±9) HU. Six patients took MRI examination. The MRI showed high or low signal of T1WI or T2WI scans.Tumor size was (4.7±3.9)cm (ranging from 1.7 to 17.5 cm). All 16 patients took operation and 11 of them took laparoscopic surgery while the other 5 cases took open surgery. Eleven cases took partial nephrectomy, 4 cases took nephrectomy and 1 case took nephroureterectomy. The surgical procedures were all successful and no complications occured during perioperative period. All cases were all confirmed metanephric adenoma by postoperative pathology and surgery cut edge were all negative. Immunohistochemical study showed that the positive rate of Vimentin, CD57, AE1/AE3, WT1, CK7 and AMACR respectively were 16/16, 15/16, 12/16, 10/16, 3/16 and 2/16. The median follow-up time of 16 cases was 44 months (ranging from 8 to 125 months) and none had recurrence or metastasis.One case died 125 months after surgery because of advanced age(83 years old). Conclusions: Metanephric adenoma is difficult to be diagnosed relying on clinical characteristics and image features. Pathology can help confirm the diagnosis. Partial nephrectomy is the first choice for operation and can achieve good prognosis. But it still needs a regular follow-up.