[Mucinous adenocarcinoma of the urachus synchronic with colorectal adenocarcinoma. Value of immunohistochemistry in the differential diagnosis].

The coincidence of an urachal adenocarcinoma with another similar tumour in other location makes necessary to separate a true primary from a metastatic adenocarcinoma. We report the case of a 66-years-old-man with an urachal mucinous adenocarcinoma and two colonic adenocarcinoma excised in the same surgical act, showing both macro and microscopic studies together with immunohistochemical techniques, that were useful to differentiate the origin of both neoplasms. Among them, the antibody to keratin 7, a cytoplasmic epithelial protein, was positive in the urachal and negative in the colonic tumour.