INTRODUCTION: Fibrosarcoma involving the pleura is extremely rare. I present a case of a young woman presenting with a pleural mass of spindle cell origin, found to be a fibrosarcoma.
CASE PRESENTATION: A 33-year-old Mongolian woman, with no known medical problems, presented with a 4 month history of right-sided chest pain and progressive shortness of breath. A computed tomographic scan of the chest revealed a large well-circumrscribed mass arising from the posterior aspect of the right lower lobe with an associated large pleural effusion (see figure1). Pleural fluid showed a lymphocytic exudate, with negative cytology. Thoracotomy revealed a 5cm mass that “popped out” of the lung and was free-floating in the pleural space. The resected mass had a fleshy tan appearance with areas of hemorrhage and necrosis. Microscopically, the tumor was composed of densely packed, regualr spindle cells showing an overlapping “herring-bone” pattern, with a moderate mitotic rate and foci of necrosis see (figure2). Immune stains showed the following results: CD31, CD34, calretinin and cytokeratins, were all negative. These results were consistent with a grade 2 fibrosarcoma of the pleura. Following surgery, the patient was discharged home with follow up with an oncologist.
DISCUSSIONS: Following radiographical analysis, the mass can be characterized as pleural based, of soft-tissue density, with an area of heterogeneous attenuation in the pleural effusion possibly consistent with blood. This pleural-based tumor may be benign or malignant. Benign tumors include benign fibrous tumors, lipomatous tumors, or multicystic mesotheliomas. Benign tumors with malignant potential include pleural thymomas and desmoid tumors. Based on the gross appearance of the resected tumors, specifically the areas of necrosis and hemorrhage, the most likely diagnosis is a primary malignant pleural neoplasm. These include localized malignant mesotheliomas, malignant solitary fibrous tumors, synovial sarcomas, and hemangiopericytomas. Based on the initial histological examination, spindle cells were identified. The differential diagnosis of a spindle cell neoplasm is rather large. In order to differentiate these, immunohistochemistry is performed. In our patient, based on immune stains, we excluded various spindle cell neoplasms such as mesothelioma of all types, synovial sarcoma, solitary fibrous tissue and hemangiopericytoma. The “herring-bone” pattern, whereby the bundle of spindle cells intersect at right angles, confirmed the diagnosis of fibrosarcoma. The grade of the fibrosarcoma tumor appears to depend on the number of mitotic figures as well as the presence of necrosis or hemorrhage. Grade 2 fibrosarcomas, as was in this case, are intermediate between grade 1 and grade 3. Grade 1 tumors have slightly larger nuclei than fibroblasts that characterize fibromatosis, and no areas of hemorrhage or necrosis. Grade 3, on the other hand, have closely packed cells with numerous mitotic figures, marked chromatin abnormalities and frequent necrosis.
CONCLUSION: This case highlights that although pleural tumors are not commonly seen, the differential diagnosis is extremely wide. Fibrosarcoma appears to be a diagnosis of exclusion based on immunohistochemistry as well as the classic “herring-bone” patttern. Pleural fibrosarcoma is very unusual, and our knowledge regarding its behaviour, prognosis and management is very limited. Nevertheless, reports have shown that prognosis appears to be related to the size and grade of the tumor.
DISCLOSURE: Serene Shashaa, None.