The Peutz-Jeghers syndrome is characterized by gastrointestinal polyposis and mucocutaneous melanin pigmentation. Between the complications are the appearance of gastrointestinal neoplasms. There is an increasing evidence suggesting the hamartoma-adenoma-carcinoma sequence in Peutz-Jeghers syndrome. We present a 32-years-old man with Peutz-Jeghers syndrome who developed an adenocarcinoma arising in a gastric hamartomatous polyp. We discuss the risk to develop gastrointestinal neoplasms and the necessity for periodic surveillance.