Neoplasia of the gastric remnant after bypass, repercussions of a delay in diagnosis.

Gastric bypass is the most frequently performed bariatric technique, with a notable increase in this procedure in recent decades. Its effectiveness in weight loss and resolution of comorbidities is well established, but it is not free from complications. Gastric remnant neoplasms after bypass develop in the excluded stomach portion, usually adenocarcinomas. Though infrequent, their risk increases due to anatomical and physiological changes induced by surgery, such as altered gastric secretion and microbiota. Early diagnosis is challenging due to endoscopic inaccessibility and nonspecific symptoms such as iron deficiency anemia or weight loss. Diagnostic delay often results in detection at advanced stages, complicating treatment and worsening prognosis. This leads to reduced survival and the need for aggressive therapies, such as radical gastrectomies or palliative chemotherapy. Close surveillance of at-risk patients is crucial.