GALT/Dome Adenocarcinoma in a Patient With MLH1-Deficient Lynch Syndrome: Navigating a Clinical and Management Dilemma.

A woman in her early 40s with MLH1-deficient Lynch syndrome was incidentally found to have a cecal gut-associated lymphoid tissue (GALT)/dome carcinoma during routine surveillance colonoscopy. This case highlights the co-occurrence of 2 rare entities: a germline MLH1 pathogenic variant and a GALT/dome carcinoma, now recognized within the lymphoglandular complex-like carcinoma spectrum, which carries potential for nodal metastasis. The intersection of mismatch repair deficiency and GALT/dome carcinoma raises a management dilemma: prophylactic colectomy vs endoscopic surveillance in the absence of high-risk histologic features. We review the literature to guide management in this rare scenario.