Abstract
RATIONALE: Lung cancer (LC) is a malignant tumor with the highest morbidity and mortality in the world. The most common metastatic sites of LC are the brain (47%), bone (36%), liver (22%), adrenal glands (15%), thoracic cavity (11%) and distant lymph nodes (10%). Peritoneal carcinomatosis (PC) is a rare clinical event in LC patients. Considering the rarity and nonspecific clinical symptoms of peritoneal metastasis among LC patients, a case of peritoneal metastasis secondary to LC incidentally observed by laparoscopic appendectomy is unusual. PATIENT CONCERNS: Here, we present a 53-year-old never-smoker woman who presented to the emergency department with a 2-day history of pain in the right abdominal quadrant. Later, laparoscopy revealed acute suppurative appendicitis accompanied by a peritoneal metastatic mass. DIAGNOSIS: The patient was diagnosed with PC secondary to metastatic LC complicated with acute suppurative appendicitis by immunohistochemistry. Positron emission tomography computed tomography (PET CT) findings further strengthen the evidence of PC from LC. OUTCOMES: Based on the results of genomic analysis, the patient received targeted therapy with osimertinib 80 mg/d. LESSONS: Due to the discovery of new targets, the use of molecular therapies improved progression-free survival (PFS) and overall survival (OS), which increases the chance of identifying peritoneal metastasis of LC. For LC patients with abdominal symptoms, clinicians should be aware of the possibility of peritoneal metastasis from LC, especially for patients diagnosed with lung adenocarcinoma or with pleural effusion.