Solitary Fibrous Tumor of the Mediastinum: A Rare Tumor at a Rare Site

The Uncommon neoplasms (<10%) of the mediastinum include neuroendocrine carcinomas, primary carcinoma of the thymus, lymphomas, germ-cell tumors, and neurogenic, endocrine, and mesenchymal tumors [1].  Solitary fibrous tumors (SFTs) of the mediastinum are rare neoplasms first reported by Witkin and Rosai [2] in 1989. Solitary fibrous tumors are usually of pleural origin but may be found in various parts of the body and are not limited to mesothelial-lined surfaces [3]. SFTs rarely metastasize [4] but need early recognition because wide and complete surgical excision may be curative in most cases. We present a rare case of giant solitary fibrous tumor of the mediastinum in a 45 year old male.

A 45 year old male presented in the out-patient clinic with complaints of progressive exercise-induced dyspnea, dry cough and constant, diffuse, left-sided chest pain for one year.On physical examination, patient had reduced left chest movements with a slightly right-deviated trachea. He had reduced tactile vocal fremitus on the left chest, as well as reduced breath sounds and vocal resonance in the middle and lower parts of anterior, lateral and posterior chest wall. Apart from hemoglobin of 9.2mg/dL and an Mean Corpuscular Volume(MCV) of 73 fl, his cell counts, electrolytes and coagulation profile were normal, as was his blood glucose level. His chest radiograph (Figure 1) showed a homogenous opacity in the left middle and lower zone, right-sided mediastinal shift, and obliterated costo- and cardio-phrenic angles. Computed tomography of the chest (Figure 2) showed marked left sided widening of the mediastinum with presence of predominantly heterogeneous mass lesion demonstrating extension into the left thoracic cavity up to the left lateral chest wall. The mass measured 14.5 x l6.7cm in its axial dimension with a craniocaudal extension of 25.1 cm, extending from the upper border of the manubrium sterni to and abutting the left hemidiaphragm with its eversion, causing right displacement of the mediastinum. It caused compression of the aortic arch, pulmonary trunk and veins, and the left atrium and ventricle. There was no pleural effusion, pleural thickening or plaque pneumothorax hilar, mediastinal, supraclavicular or axillary lymphadenopathy. A transcutaneous ultrasound-guided trucut biopsy of the tumor showed spindle cell tumour, consistent with SFT. After pre-op work-up and consent, left thoracotomy and resection of the tumor was performed and solid tumor, measuring 32 x 30 x 10 cm, was removed in multiple pieces (Figure 3). In contrast to the CT findings, the tumor had not infiltrated adjacent structures and the lung expanded up to the chest wall after resection. On gross appearance, tumor was partially encapsulated multinodular firm with its cut surface being tan white to brown lobulated surface, and areas of hemorrhage and myxoid degeneration. Its microscopic examination revealed spindle cells arranged in short fascicles and storiform pattern. Cells had round to oval hyperchromatic nuclei with scant cytoplasm. The neoplastic cells were arranged in collagenized stroma. Areas of hyalinization were also seen. Approximately 5 mitoses/10 HPF were seen. Special stain PAS+/-D did not highlight glycogen in the neoplastic cells. Immuno-histochemical stains performed were positive for CD34, ASMA (patchy), but were negative for cytokeratin AEl/AEB, desmin, S-100, CD31, and EMA. Our patient made an uneventful recovery and was discharged on the seventh post-operative day. At six months of follow-up, patient was symptom- free and showed no evidence of recurrence of disease.