The authors report a case of urachal carcinoma of a 60 year old woman of particular interest because of the clinical history, biological behavior and histotype. The tumor presented as an umbilical mass of 25 cm which had slowly increased during 20 years without evident clinical signs or infiltration of the peritoneum and abdominal organs. Histologic findings revealed an adenosquamous carcinoma, which represents less than 5% of urachal neoplasms. Surgical excision is the treatment. The prognosis is poor because of regional recurrence and metastases. The authors review the literature analyzing the criteria for differential diagnosis between adenocarcinoma of vesical and of urachal origin.