Primary Extraskeletal Mesenchymal Chondrosarcoma of the Anterior Mediastinum
A 21-year-old woman visited an outside hospital with the chief complaint of intermittent chest discomfort and respiratory difficulty for 2 months. In the medical history, the patient had taken medication for schizophrenia for several years. On the chest computed tomography (CT) scan, the patient had a 13-cm heterogeneous enhancing mass with multifocal calcification in the anterior mediastinum that invaded the pericardium and was associated with massive left pleural effusion. The mass encased the aortic arch and branch along with the left and main pulmonary arteries, but did not appear to be originating from the osteocartilaginous structures of the thoracic region (). The patient then underwent a CT-guided needle biopsy, for which a diagnosis of solitary fibrous tumor was suggested on a biopsy. Then, the patient was referred to the Dong-A University Medical Center to confirm the diagnosis and undergo further treatment. Although the tumor could not be resected completely due to the extensive invasion into the main vessels, a surgical excision of the mass along with wedge resection of the left upper lung and partial resection of the pericardium was performed. The tumor at the time of surgery was found to invade the pericardium and to be tightly adhered to the left upper lung. However, it could be easily separated from the adjacent ribs. The resected tumor, measuring 13×7.5 cm, was solid, lobulated, and partially covered by a thin fibrous capsule. On the cut section, the tumor was tan white, and soft to fish-flesh, while the lobulated cut surface exhibited focal areas of irregularly sized glistening cartilage and coarse calcification (). Microscopically, the lesion was composed of a highly cellular proliferation of undifferentiated round, oval, or spindle-shaped cells with an abrupt transition with small islands of well-differentiated hyaline cartilage, frequently associated with central calcification and ossification (). In some areas, the undifferentiated cells were separated by branching, sinusoidal vascular channels imparting the lesion with a hemangiopericytoma-like pattern (). Immunohistochemically, the cartilaginous portion of the tumor showed S100 protein positivity, but the undifferentiated cells showed negative immunoreactivity for the S100 protein (). Undifferentiated cells showed strong membranous immunoreactivity for CD99, whereas only isolated cells in the cartilaginous portion stained for CD99 (). The tumor cells exhibited negative immunoreactivities for cytokeratin and CD34. The patient made an uneventful postoperative recovery and was discharged on postoperative day 5 with advice to undergo chemotherapy and local radiotherapy. However, the patient refused any further treatment. The patient is still alive with a residual tumor at the time of writing this report (8 months postoperatively).