The authors describe a rare case of mucoepidermal carcinoma of the lung incidentally identified in preoperative assessments for inguinal hernia repair in a 5-year-old girl. This patient was referred for right external inguinal hernia, and a 3.0-cm round-shaped lesion was found in the right lower lung field of a chest x-ray film. She had no respiratory tract complaints, but her serum carcinoembryonic antigen concentration was markedly elevated (21.2 ng/mL). Chest and abdominal computed tomography/magnetic resonance images could not determine the nature of the lesion, but 2-[18F]fluoro-2-deoxy-d-glucose positron emission tomography (FDG-PET) indicated a malignant tumor pattern.
