Primary adenocarcinoma of the navel: an uncommon entity.

Malignant tumors in the umbilical region are uncommon, although they represent more than 10% of malignant neoplasms that affect the skin of the anterior wall of the abdomen. This anatomical region is home to numerous vascular and embryological connections with the abdominal organs, which favors the appearance of metastases derived from different visceral tumors. Nonetheless, primary umbilical tumors make up only 20% of the malignant tumors in that location, and very few cases have been reported to date. We report the diagnostic/therapeutic sequence followed in a patient with a primary adenocarcinoma in the umbilical region, and also review the limited related scientific literature. The patient was a 60-year-old male who presented with a painless non-reducible nodule in the umbilical region that had been progressively growing over the course of the previous year. Upon physical examination, we observed a round tumor formation that was attached to deep planes and measured some 3 cm in diameter. Abdominal ultrasound revealed a solid umbilical mass measuring 3 cm 2 cm affecting the left anterior rectus. The fine needle aspiration (FNA) sample was compatible with adenocarcinoma. The cytology report, including immunohistochemistry study, showed a possible biliopancreatic origin as the first option and proposed that the lesion could possibly be a primary umbilical adenocarcinoma if no other origin was found (Fig. 1). The patient underwent gastroscopy, colonoscopy, thoracic and abdominal computed axial tomography (CT) scans (Fig. 2), magnetic resonance cholangiopancreatography and even positron-emission tomography (PET) with the intention to rule out the presence of a primary tumor in another location. All of the tests came back normal. We performed a midline laparotomy with en bloc resection of the navel, tumor and a portion of the left anterior rectus muscle that was affected. We explored the rest of the abdominal cavity, with normal findings. Postoperative recovery was favorable, and the patient was discharged from the hospital 48 h after the intervention. The pathology study reported findings compatible with well-differentiated infiltrating adenocarcinoma (Fig. 3). As no internal adenocarcinoma was found, it was concluded that the mass was a primary umbilical adenocarcinoma arising from the urachus. Seven months after the intervention, the patient is asymptomatic, with normal tumor marker levels and no evidence of locoregional or distant disease. The navel region can be a host to a large variety of benign tumors. Malignant tumors, which are much less frequent, are mostly metastases of an abdominal neoplasm and, to a