Acute appendicitis caused by metastatic adenocarcinoma from the lung: a case report

Background: Appendiceal metastasis from lung cancer is rare. However, it often causes acute appendicitis that requires emergency surgery. We herein report a thought-provoking case of appendiceal metastasis from lung cancer. Case presentation: A 71-year-old man was diagnosed with advanced lung cancer with multiple metastases and underwent chemotherapy. One month later, he developed acute appendicitis, and laparoscopic appendectomy was promptly performed. A swollen appendix and pus collection were observed during surgery. Histological analysis revealed an invasive adenocarcinoma in the appendix that infiltrated the mucosal, submucosal, and muscular layers. Positive immunostaining of thyroid transcription factor 1 indicated appendiceal metastasis of pulmonary adenocarcinoma, not a primary appendiceal malignancy. The postoperative course was uneventful, and the patient's pulmonary internist resumed continuous chemotherapy after surgery. Conclusions: Although appendiceal metastasis from pulmonary adenocarcinoma is rare, it often results in acute appendicitis. Optimal therapy including emergency surgery should be performed without hesitation so that chemotherapy can be resumed as soon as possible.