PET scanning may not distinguish benign schwannoma from metastasis in a patient with lung adenocarcinoma

A 69-year-old man was diagnosed with lung adenocarcinoma with metastasis because two masses in the right intercostal space and right back muscle showed high accumulation on positron emission tomography (PET). The 6-month treatment with osimertinib significantly reduced his lung lesion, but no changes were observed in the metastatic lesions. Needle biopsy revealed that the lesion in the right back muscle was a schwannoma. Surgical resection revealed that the right intercostal lesion was also a schwannoma; subsequently, a right upper lobectomy was performed. The patient was finally diagnosed with lung adenocarcinoma without metastasis. High accumulations of lesions observed on PET may indicate schwannomas