Medullary adenocarcinoma of the ascending colon mimicking appendicitis after prior appendectomy.

Medullary adenocarcinoma is a rare colorectal carcinoma that may be difficult to recognize when inflammation dominates the presentation. A 65-year-old woman with a remote appendectomy presented with 1 month of postprandial abdominal pain, weight loss, and constipation. Repeated computed tomography demonstrated marked pericecal inflammation and a blind-ending structure interpreted as possible appendicitis despite her surgical history. Diagnostic laparoscopy identified an enlarged mesenteric lymph node, and excision unexpectedly showed metastatic medullary carcinoma of colonic origin with loss of MutL homolog 1 and PMS1 homolog 2 genes. Subsequent evaluation identified an ascending-colon primary. Right hemicolectomy confirmed a 1.5 cm poorly differentiated medullary adenocarcinoma, staged as pT2 pN1b, with negative margins. The patient remains clinically well during oncologic treatment. Persistent appendicitis-like inflammation, particularly when discordant with prior appendectomy, should prompt evaluation for cecal or ascending-colon malignancy.