Unusually early presentation of small-bowel adenocarcinoma in a patient with Peutz-Jeghers syndrome.

Peutz-Jeghers syndrome (PJS) is an autosomal dominant cancer predisposition syndrome characterized by melanotic macules and hamartomatous polyps. Small-bowel surveillance in the pediatric PJS population is not designed to identify small-bowel malignancy, which is thought to arise in adulthood. A 13-year-old boy presented with lead-point intussusception, requiring emergent surgical resection. A mucinous adenocarcinoma was found arising from high-grade dysplasia within a polyp. On the basis of these findings and mucosal pigmentation, he was diagnosed with PJS. DNA sequencing revealed a heterozygous c.921-1G>T STK11 mutation. This case is the earliest onset of small-bowel carcinoma in PJS, an observation relevant to surveillance guidelines.