Most reports describe an increased risk of malignancy in Peutz-Jeghers syndrome (PJS). We identified individuals with PJS-like pigmentation but no polyposis, designated as isolated mucocutaneous melanotic pigmentation (IMMP), and 1)characterized their clinical features, 2) assessed them for cancer events, and 3) screened a sample of these subjects for mutations in LKB1, a gene responsible for a portion of PJS cases. Review of Mayo Clinic records from 1945 to 1996 identified 26 patients with IMMP. All were then interviewed or their medical records reviewed to determine if cancer had developed. Conformation-sensitive gel electrophoresis (CSGE) screening for LKB1 mutations was followed by direct sequencing. Ten of these 26 individuals (38%) developed 12 malignancies that arose in the cervix (n = 3), endometrium (n = 3), breast (n = 1), kidney (n = 1), lung (n = 2), colon (n = 1), and lymphatic tissue (n = 1). In females with IMMP, the relative risk for cancer was 3.2 (95% CI, 1.2-6.9), while that for males was not increased. The relative risk for breast and gynecologic cancers was 7.8 (95% CI, 2.5-18.1) in affected females. Of 9 individuals tested, no LKB1 mutations were detected. Classical PJS is associated with an increased cancer risk. Our results indicate that IMMP is another lentiginosis with cancer predisposition. In particular, the relative risk for cancer in females with IMMP was significantly increased, as is true in females with PJS. However, LKB1 mutations did not contribute to the development of IMMP in the patients tested.
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