Peutz-Jeghers syndrome (PJS) is a classic, but not widely known hereditary trait [1, 2]. Its clinical hallmarks are intestinal hamartomatous polyposis and melanin pigmentation of the skin and mucous membranes. In addition, PJS predisposes to cancer [3, 4]. The most common malignancies are small intestinal, colorectal, stomach and pancreatic adenocarcinomas. Other cancer types that probably occur in excess in PJS families include breast and uterine cervical cancer, as well as testicular and ovarian sex cord tumors. The relative risk of cancer may be as high as 18 times that of the general population, and the cancer patients' prognosis is reduced. Recently, the predisposing locus was mapped to 19p13.3 using a novel method [5]. Subsequently, the causative gene was shown to be LKB1 (a.k.a. STK11), a serine/threonine kinase of unknown function [6]. Although preliminary reports seem to suggest a minor role for LKB1 in sporadic tumorigenesis [7-12], further investigations are needed.