Urachal cystadenoma with abundant glycogen: ultrastructural study.

A cystadenoma arose in the urachus of a 32-year-old man. The mass was a multilocular cystic tumor filled with light yellow mucoid material. It was located in the anterior abdominal wall between the umbilicus and the dome of the urinary bladder. Overall, the mass was 14 cm x 8 cm x 5 cm, with the largest internal cyst being 6 cm in diameter. The lesion was characterized histologically by columnar cells with focal cellular and nuclear stratification. Ultrastructural examination revealed columnar cells with abundant glycogen, moderately pleomorphic microvilli without prominent filamentous cores, and apical mucin vacuoles. Nuclei had pleomorphic contours. An intact basal lamina was present. A similar urachal cystadenoma has not been described.