[Colloid carcinoma of the urachus. Cytologic diagnosis and differential diagnostic classification].

We report a rare case of colloid carcinoma apparently of urachal derivation. In a patient presenting with nycturia cytological analysis of urine led to a tentative diagnosis of colloid carcinoma of urachal origin. Endoscopic and radiological investigations confirmed this provisional diagnosis. For this reason, the surgical procedure could be properly planned and restricted to the removal of the apex of the bladder and urachus.