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. LEARNING POINTS: Benign schwannomas could show high accumulations on positron emission tomography. Accurate diagnosis of schwannoma using only images is quite challenging. Histological examinations should be considered when asymptomatic lesions are suspected to be metastases.