A mediastinoscopy was done, and the lymph nodes sampled were negative for malignancy. A positron emission tomography scan was negative for primary malignancy elsewhere in the body. The patient's pneumonia worsened, and postobstructive necrotizing pneumonia developed despite treatment with broad-spectrum antibiotics.
A right pneumonectomy with mediastinal lymph node resection was done. The pneumonectomy specimen demonstrated a 6.5 × 4.5 × 4-cm mass surrounding the bronchus intermedius and extending to the right lower lobe. The tumor was diagnosed as an infiltrating synovial sarcoma involving the diaphragm and mediastinum, but the mediastinal lymph nodes and surgical margins were free of the tumor.
The specimen stained positive for vimentin, epithelial membrane antigen (EMA), cytokeratin antibody (AE1/AE3), smooth muscle actin, CK19, CD99, and BCL2. The specimen's histological appearance and strongly supportive immunohistochemistry confirmed the diagnosis of biphasic synovial sarcoma (Figure 3).
Figure 3 – Spindle cells (arrow) with positive cytokeratin staining can be seen in this histopathological specimen.
The patient's postoperative course was uneventful, and he was discharged home. He is doing well after approximately 9 months of outpatient follow-up.
Discussion
Pulmonary sarcomas are divided into 4 categories: leiomyosarcomas, fibrosarcomas, hemangiopericytomas, and synovial sarcomas. Pulmonary sarcomas are usually parenchymal and metastatic in origin. Primary pulmonary synovial sarcoma is an extremely rare tumor that may arise from the lung parenchyma, bronchial tree, or pulmonary artery. This type of sarcoma was underdiagnosed before the use of immunohistochemistry and electron microscopy.
