[Intramuscular myxoma of intercostal muscle; report of a case]

A 72-year-old woman was reffered to our hospital for further examination of a tumor shadow in the left upper lung field which was detected in a mass screening chest X-ray. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a chest wall tumor located in the left 4th intercostal space. The lesion was suspected to be neurogenic tumor and CT-guided needle biopsy was performed. The tumor was consisted of spindle-shaped cells, but immunohistochemistry demonstrated no evidence of neurogenic tumor. As a possibility of malignant tumor could not denied, we performed tumor resection under video-assisted surgery. The lesion was not originated from nerves, but adhered to the intercostal muscle. Histologically, the tumor was consisted of spidle-shaped cells without atypia which sparsely proliferate in the myxoid stroma adjacent to intercostal muscle. In immunohistochemistry, tumor cells were positive for vimentin, and negative for desmin, S-100 protein, smooth muscle actin, CD34 and factor VIII. It was diagnosed as intramuscular myxoma. This histology in the intercostal muscle is extremely rare.