SOLITARY JUVENILE POLYP DEVELOPING ADENOCARCINOMA WITH SUBMUCOSAL INVASION

Solitary juvenile polyps are generally non-neoplastic hamartomatous polyps. Inflammation is suggested as the cause of proliferation and progression of these polyps, and adenomatous and carcinomatous changes are rare. We report a rare case of a solitary juvenile polyp with malignant transformation that developed in the sigmoid colon of a 12-year-old boy. A 3 cm, pedunculated polyp was endoscopically resected, and histologic evaluation revealed the characteristic features of a juvenile polyp. However, mucous-filled ectatic glandular spaces were lined by mucin-secreting columnar epithelial cells with atypical change, and an admixture of adenocarcinoma invading the submucosa was confirmed. The histologic features may suggest the involvement of the adenoma–carcinoma sequence in the development of adenocarcinoma in the present case. Although rare, solitary juvenile polyps should develop adenocarcinoma and thorough histologic evaluation of the resected polyps is warranted to identify the adenomatous tissue.