Lung cancer as a predominant feature in a patient with Peutz-Jeghers syndrome: Case report.

Peutz-Jeghers syndrome (PJS) is characterized by mucocutaneous pigmentation and gastrointestinal hamartomatous polyposis, which can lead to intussusception. PJS patients face high lifetime risks for various cancer types, with the majority of patients being diagnosed with tumors along the gastrointestinal tract. Herein, we present the case of a 34-year-old man who carried a germline STK11 pathogenic variant, while lacking the cardinal features of PJS syndrome. Interestingly, he was diagnosed with lung adenocarcinoma despite being a never-smoker. Tumor testing revealed clinically relevant molecular alterations, including the known germline pathogenic variant STK11, a KRAS somatic pathogenic variant, and FGFR3 gene amplification. Treatment with standard chemotherapy and immunotherapy did not have a clinical benefit. Due to clinical deterioration, the patient deceased 18 months after his initial diagnosis prior to having the chance for targeted therapy. Identification of rare hereditary cancer syndromes and the respective presence of tumor biomarkers can provide important alternatives to targeted treatments, including immunotherapy in patients with tumors unresponsive to conventional treatment protocols. This case highlights that although only a small proportion of lung cancer diagnoses will be due to hereditary predisposition, STK11 germline carriers should be under close surveillance for early detection of lung cancer.