Metachronous Breast and Lung Cancers in a Middle-Aged Woman with Peutz-Jeghers Syndrome

We report the case of a middle-aged woman with Peutz-Jeghers syndrome who developed metachronous breast and lung cancers, because lung cancer is infrequently associated with PJS, especially for women with this disorder. At the age of 12 years, the patient was diagnosed with Peutz-Jeghers syndrome owing to the presence of multiple hamartomatous polyps in the gastrointestinal tract and mucocutaneous melanin pigmentation. She developed breast cancer and underwent curative mastectomy and postoperative adjuvant chemotherapy at 48 years of age. Five years later, computed tomography showed multiple lung nodules. The pathological diagnosis of the lung lesion was a mucinous adenocarcinoma, which differed from that of the resected breast cancer. She then received cisplatin/ pemetrexed therapy combined with pembrolizumab for non-small cell lung cancer, which reduced the size of the lung tumors. However, the disease eventually progressed, and she underwent a gene panel test because of the refractoriness to pharmacotherapy, which demonstrated a germline STK11 pathogenic variant.