Peutz-Jeghers Syndrome With Malignant Transformation in a Hamartomatous Rectal Polyp: A Case Report.

Peutz-Jeghers syndrome (PJS) is a rare hereditary condition characterized by mucocutaneous pigmentation and hamartomatous gastrointestinal polyps. We describe the case of a 14-year-old girl who presented with rectal bleeding, in whom endoscopic evaluation revealed multiple hamartomatous polyps, including two large rectal lesions. Histopathological analysis showed areas of high-grade dysplasia and in situ carcinoma developing within a hamartomatous polyp. Although this syndrome is generally benign, affected individuals have a lifelong predisposition to gastrointestinal and extra-digestive malignancies. Malignant transformation during adolescence is exceptionally uncommon, highlighting the importance of early diagnosis and structured surveillance to reduce cancer risk.