ABSTRACT
The authors report two cases of patients with appendix adenocarcinoma, manifested as a syndrome of abdominal tumor of unknown origin. It was not possible to perform etiological diagnosis in the preoperative period for any of them. Literature data show that large locoregional tumor is a manifestation of appendix adenocarcinoma, although acute appendicites is the most frequent clinical manifestation. Preoperative diagnosis is rare and usually performed during laparotomy or through histopathological examination of the specimen. In large tumors, total mass resection including hemicolectomy should be carried out whenever possible. Whenever diagnosis of appendix adenocarcinoma is performed by the histopathological examination of the acute appendicites specimen, re-intervention is indicated for a right hemicolectomy.