Mucinous cystadenoma of the pyelocaliceal system: a report of 3 examples and an analysis of 17 previously published cases.

We report 3 patients all men between 45 and 64 years of age with unilocular or multilocular mucinous cystadenomas of the kidney. One tumor arose from the renal pelvis, and 2 involved the entire pyelocaliceal system. The tumors measured between 2.4 and 37 cm in greatest dimension. Two patients were asymptomatic, and 1 had recurrent attack of acute pyelonephritis. Microscopically, the morphology and immunophenotype (CK20, MUC2, and CDX2 positive) of the tumors were similar to the colonic adenomas. Two patients were asymptomatic 24 and 64 months after surgery, including the patient with mucinous cystadenoma and intramucosal carcinoma. One patient died of acute myocardial infarction, and his tumor was an autopsy finding. Only 17 cases of mucinous cystadenomas and 5 cases of mucinous cystadenocarcinomas have been reported. Of the 17 mucinous cystadenomas, 2 arose in horseshoe kidneys. The mean size of these neoplasms was 15 cm (2.4-37 cm). Despite their large size, some patients with mucinous cystadenomas were asymptomatic. Sixty percent were associated with renal lithiasis. Thirty percent progressed to mucinous adenocarcinomas, and only 2 cases showed areas of intramucosal carcinomas. Two cases were associated with carcinoid tumors, similar to those reported in the appendix. Most patients were asymptomatic after surgery, and only 1 patient died by abdominal sepsis related to adenomucinosis. The 3 examples of mucinous cystadenomas of the pyelocaliceal system reported here, and those previously published indicate that they are very uncommon neoplasms with morphology and intestinal immunophenotype similar to the colonic adenomas.