Two lung adenocarcinomas in the same lobe: multiple primaries or intrapulmonary metastasis?

Abnormal nodules were found in the left lung of a 52-year-old woman in segments 6 and 10 on a chest CT. These nodules showed no changes for 18 months, and we discontinued follow-up. Almost 5 years later, an abnormal shadow was found in her left lower lung field on a medical check-up chest X-ray. Chest CT revealed that the left segments 6 and 10 nodules had grown. We diagnosed these lesions as synchronous double primary lung cancers in the same lobe based on the disease history and performed a left lower lobectomy and lymph node dissection. Pathological examination of both tumors revealed adenocarcinoma of a mixed subtype with papillary and bronchioloalveolar carcinoma. Epidermal growth factor receptor gene mutations were examined, and the 2 lesions shared an L858R mutation. Although we expected EGFR gene mutation analysis would help us distinguish the 2 lesions from each other, it was of little help. Disease history can be more important in evaluating multiple pulmonary cancers.