A 65-year-old nonsmoker, a woman with a medical history negative for cancer, was admitted to the hospital because of chest pain and dyspnea. On physical examination, breath sounds were diminished at the left lung base. The findings of hematologic laboratory tests, including those for serum tumor markers (ie, carcinoembryonic antigen, CA19.9, and CA125), as well as arterial blood gas analyses were unremarkable. Chest radiographs showed a large solid mass occupying the left upper thoracic cavity almost completely. A chest and abdomen CT scan confirmed the presence of a solid mass with central necrosis, 12 cm across, possibly arising from the mediastinum or the pleura with concomitant pleural effusion. The mass compressed the left central bronchial and vascular structures as well as the main branch of the left pulmonary artery, apparently without infiltration of the lung parenchyma (Fig 1
, top left, A). Neither lymph node enlargement nor other lesions outside the chest was detected. Bronchoscopy showed a narrowing of the left main bronchus, but BAL fluid cytology findings were negative. A transthoracic biopsy revealed a spindle cell proliferation of bland-looking elements dissected by collagen bands that strongly reacted with CD34 and bcl2, and were admixed with a clear-cut, high-grade malignancy that was characterized by spindle-shaped cells with prominent nucleoli and a high mitotic rate that reacted with vimentin, but not with the other tested immunohistochemical markers (ie, CD34, bcl2, smooth-muscle actin, desmin, cytokeratins, h-caldesmon, CD117, CD21, CD10, CD31, and estrogen receptors). A diagnosis of malignant SFT was determined. The patient then underwent surgical excision of the mass, which, on intraoperatory examination, was determined to originate from the left pleura with infiltration of the left upper pulmonary lobe. Several other small pleural nodules were also excised, but the tumor was not radically resected. Grossly, the mass had a whitish cut surface with hemorrhagic areas and central necrosis. Histologically, the tumor displayed the double component seen on biopsy specimens (Fig 1, top right, B). In fact, the minority of the mass consisted of a typical SFT with bland spindle cells arranged in a “patternless” pattern, separated by bands of hyaline “keloid-type” collagen and with a peculiar “hemangiopericytoma-like” vascular network (Fig 1, middle left, C). At the periphery, the presence of a high-grade neoplasm that was characterized by spindle cells with a high mitotic rate was noted (Fig 1, middle center, D). The low-grade component had the characteristic CD34+/bcl2+ immunoprofile (Fig 1, middle right, E), while the sarcomatous tumor part reacted with vimentin only. Of note, both components stained for PDGFRβ (Fig 1, bottom left, F). A diagnosis of pleural malignant SFT with sarcomatous overgrowth was performed. During molecular analysis by a direct-sequencing polymerase chain reaction of exons 12, 14, and 18 in the PDGFRβ gene, a missense puntiform mutation was detected on exon 18 (Asp850 was substituted for Val) encoding for the protein kinase domain in the sarcomatous component only (Fig 1, bottom right, G). The postoperative course was uneventful, but the patient died 2 months after undergoing surgery for acute respiratory and cardiovascular failure due to intrathoracic tumor growth.