42 Composite intestinal adenoma-microcarcinoid: A comprehensive update

Abstract Introduction/Objective Composite Intestinal Adenoma-Microcarcinoid (CIAM) is a rare colorectal entity that predominantly presents as an adenomatous polyp. It combines a benign adenoma with microscopic neuroendocrine (NE) aggregates (microcarcinomas). CIAM’s rarity and potential to mimic other lesions pose significant diagnostic challenges. Methods/Case Report We conducted a systematic literature review (PubMed/MEDLINE 1975-2025) using relevant terms. After screening 62 articles, 23 relevant publications were reviewed to investigate the clinical, pathological, and diagnostic features of gastrointestinal CIAM. Results CIAM is observed in the colorectal region, particularly in the caecum, among elderly males. Histologically, it comprises an often high-risk adenomatous component interspersed with microcarcinoids at the glands’ base. Immunohistochemistry reveals positivity for neuroendocrine markers (synaptophysin and INSM1+). Often diagnosed incidentally via routine screening, as they are asymptomatic. Differentiating them from invasive adenocarcinoma is crucial. CIAM lesions are generally benign and lack common colorectal mutations like KRAS and BRAF. Conclusion The incidence of CIAM remains uncertain due to limited literature, yet it is increasingly recognized as important given its potential for misdiagnosis with more aggressive conditions. Accurate diagnosis is crucial for distinguishing CIAM from malignant lesions and ensuring appropriate clinical management and follow-up. Further research is needed to understand better CIAM’s pathogenesis, molecular features, and long-term outcomes.