The tumor is composed of signet ring cells. Other areas showed enteric (intestinal) differentiation with abundant extracellular mucin production. Some cases have low-grade histology and are associated with pseudomyxoma peritonei. The tumor is usually centered in the muscularis propria. Urothelial mucosa is intact in early stages but may become ulcerated later as the tumor enlarges. The differential diagnosis of urachal adenocarcinoma includes primary adenocarcinoma of bladder, direct extension or metastases from colonic adenocarcinoma, and urothelial carcinoma with glandular differentiation.