A solitary Peutz–Jeghers (PJ) polyp is a rare hamartomatous lesion without an associated PJ syndrome. However, little is known regarding malignancy arising in solitary PJ polyps. Here, we report a case of a solitary colonic PJ polyp with focal dysplasia. A 45-year-old asymptomatic man underwent total colonoscopy following a positive fecal occult blood test. The patient had no history of mucocutaneous pigmentation or family history of PJ syndrome. A 20 mm erythematous pedunculated polyp was observed in the sigmoid colon. Magnified endoscopy revealed a tubular or branch-like pit pattern with localized areas of irregular pits. These findings were suggestive of colorectal adenoma with high-grade dysplasia, and endoscopic mucosal resection was performed. Histopathological examination revealed arborizing proliferation of hyperplastic epithelia with smooth muscle bundles. In addition, a small number of irregular crypts with high-grade dysplasia were observed in the hyperplastic epithelium. Based on these histological findings, we finally diagnosed the patient with a solitary colonic PJ polyp with high-grade dysplasia. The present case suggests that solitary colonic PJ polyps may harbor dysplastic changes and require pathological evaluation with en bloc resection of the polyps.
