Twenty years ago, a 45-year-old woman with a recent diagnosis of breast cancer went to see a dermatologist, who noted hyperpigmentation of her lips. The dermatologist clinically diagnosed her as having Peutz-Jeghers syndrome (PJS), a rare genetic condition that often starts with characteristic benign polyps in the gastrointestinal tract and increases the risk of breast, intestinal, pancreatic, and other cancers. The first signs of the condition include dark skin freckles around and inside of the mouth, eyes, nostrils, genitalia, and fingers, which usually show up in the first decade of life and often fade in adolescence or by adulthood.

According to the National Comprehensive Cancer Network’s guidelines, if a patient has a pathogenic variant in the STK11 gene, he or she has PJS. However, 5 percent of patients with PJS do not have an identifiable STK11 pathogenic variant, and in those cases, patients are clinically diagnosed with PJS if they meet at least two of the following criteria: PJS-type polyps in the GI tract; hyperpigmentation around the mouth, lips, and other specific areas; or a family history of the condition.

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