Pathologic Quiz Case: Pulmonary Mass in a Patient Presenting With a Hemothorax

A 59-year-old white woman was admitted to the hospital with a chief complaint of cough and shortness of breath. She stated that her coughing started 6 days prior to admission and had gotten worse. She reportedly had been taking antibiotics for 4 days but was not improving. She also described feeling feverish with chills. She denied any nausea, vomiting, chest pain, diarrhea, hemoptysis, or significant weight change. Physical examination was remarkable for decreased breath sounds bilaterally and dullness to percussion at the base of the right lung. Vital signs included an elevated temperature of 37.8°C (100.1°F). Laboratory findings were remarkable for an elevated white blood cell count of 12.9 × 109/L. A chest radiograph revealed a right pleural effusion and a right anterior mid lung mass–like lesion (Figure 1). Computed tomography and fine-needle aspiration were performed but were both relatively nondiagnostic. A few days after admission, the patient's hemoglobin and hematocrit values dropped significantly. A repeat chest radiograph at that time revealed a complete whiteout of the right lung. The attending physicians believed that the patient had developed a hemothorax, and she was taken to the operating room. At the time of surgery, the patient was found to have a hemothorax as suspected, but also a thick pleural rind and a large pulmonary mass involving the right upper and middle lobes.The right upper and middle lobes, as well as decortication material from the pleural rind, were sent to pathology. Grossly, the decortication material consisted of several fragments of yellow friable material with areas of necrosis and hemorrhage that measured in aggregate 15 × 13 × 5 cm. Examination of the upper and middle lobes of the right lung revealed an irregularly shaped, yellow, gray-tan friable mass that measured 9 × 6.5 × 2 cm. The mass shelled away from the remainder of the lung, and cross sections of the mass revealed necrotic and hemorrhagic areas.A touch imprint of the mass (Figure 2) revealed a spindle cell population. The cells had a scant amount of delicate cytoplasm and slightly hyperchromatic nuclei with fine chromatin. Nucleoli were small, and mitotic figures were not readily identified. Hematoxylin-eosin–stained permanent sections revealed similar findings, with a monomorphic population of spindle cells. The cells were arranged in short fascicles alternating with more haphazardly arranged spindle cells, which gave the tumor an overall marbleized appearance (Figure 3). A few cells with a more epithelioid-like appearance were identified among the spindle cells. Areas of necrosis were identified, and the number of mitotic figures ranged between 4.5 and 10.5 per 10 high-powered fields (hpf). Immunohistochemical staining revealed positivity for pancytokeratin (AE1/AE3) (Figure 4), cytokeratin 7, epithelial membrane antigen, bcl-2 protein, vimentin, and BerEP4. Immunohistochemical stains for chromogranin, S100 protein, and actin were negative.What is your diagnosis?Classically, synovial sarcomas have been thought of as a sarcoma of the extremities near large joints, especially the knee.1 Other sites that reportedly have been affected include the head and neck, trunk, abdominal wall, heart, mediastinum, and pleural cavity.2,3 Synovial sarcomas only recently have been recognized as a primary pulmonary malignancy. In 1995, Zeren et al4 studied 25 cases of pulmonary sarcoma that also had clinicopathologic, immunohistochemical, and ultrastructural features of synovial sarcoma. They concluded that these cases represented synovial sarcoma, which previously had not been reported to occur in the lung. Later in 1995, Kaplan et al2 also reported a case of a primary pulmonary monophasic synovial sarcoma with the chromosomal translocation t(X;18), which is characteristic of synovial sarcoma.The morphologic features of the case described herein are very similar to the cases Zeren et al described, as well as to the more classically located synovial sarcoma. The clinical features of the current case are also similar to the clinical findings in the cases studied by Zeren et al. Common findings in association with pulmonary sarcoma in that study included chest pain, hemoptysis, and shortness of breath.4 Patients in that study ranged from 16 to 77 years of age, and there was a female predominance (M:F = 1:1.3).4 These findings are in contrast to the synovial sarcomas seen in the extremities, which are painful tumors of young adults between the ages of 15 and 40 years and affect males more commonly than females.1The gross features described by Zeren et al consist of a nonencapsulated tumor with necrosis, hemorrhage, and cystic changes. The tumors ranged in size from 0.6 to 20 cm. These findings are similar to those described both in our case and in the more typically located synovial sarcomas. Our case also had cytologic features consistent with a typical synovial sarcoma, including moderate to marked cellularity with cells arranged in aggregates and singly spaced.5 The cells often have hyperchromatic nuclei with scant tapering cytoplasm.5 Nucleoli are small to inconspicuous, and mitoses are scarce.5 In cases that are biphasic, epithelial cells are often identified.5 Although we did not appreciate these findings initially on the touch imprint, they were identified focally on permanent sections.Histologically, synovial sarcomas have been divided into 3 categories: fibrous biphasic, fibrous monophasic, and epithelial monophasic. We felt our case represented a fibrous biphasic synovial sarcoma. We found several similarities between our case and those described by Zeren et al.4 Those authors found their cases consisted of an atypical spindled proliferation of plump cells with oval nuclei. In some areas, the cells had an epithelioid appearance with round to oval cells with inconspicuous nucleoli. Necrosis was identified in all the tumors, and the mitotic rate ranged from 2 per 10 hpf to more than 20 per 10 hpf.2 Additional findings Zeren et al noticed that were not present in our case included myxoid change, neural-like palisading, and osteoid metaplasia.2Special techniques, including immunohistochemistry and cytogenetics, are often helpful in making the diagnosis of synovial sarcoma. Immunohistochemical staining patterns classically found in synovial sarcomas include S100 protein negativity and positivity for vimentin, cytokeratin, and epithelial membrane antigen.1 In this case, the pancytokeratin demonstrated well-defined glandular structures, which allowed us to identify the tumor as a biphasic synovial sarcoma. Additionally, we found this tumor to be immunoreactive for the bcl-2 protein. Immunoreactivity for bcl-2 protein can be particularly helpful in separating synovial sarcoma from other possibilities in the differential diagnosis, including leiomyosarcoma, malignant peripheral nerve sheath tumor, and fibrosarcoma. Hirakawa et al6 examined 19 cases of synovial sarcoma and 29 additional soft tissue spindle cell sarcomas and identified bcl-2 protein positivity in 79% of the synovial sarcomas and negative immunohistochemical staining for bcl-2 protein in all leiomyosarcomas, malignant peripheral nerve sheath tumors, and fibrosarcomas examined. They further suggested that the bcl-2 positivity might be linked to the classic chromosomal translocation associated with synovial sarcoma, as they both involve chromosome 18.6 In more than 90% of cases of synovial sarcoma, the classic translocation t(X;18)(p11;q11) can be identified.7 This involves the SYT gene on chromosome 18q11 and 2 genes, SSX1 and SSX2, on Xp11.5 The SSX1 and SSX2 genes are closely related; however, the function of these genes is unknown.7Because of the pleural rind identified at surgery in our case, we considered the possibility of a malignant mesothelioma. However, we identified several characteristics in this case that allowed us to conclude this was a synovial sarcoma and not a malignant mesothelioma. These features included the presence of a lung mass as opposed to the multiple pleural-based nodules usually seen in malignant mesothelioma; the histologic presence of long fascicles, unlike the short fascicles seen in malignant mesothelioma; and the positive immunoreaction to BerEP4 in our case (typically negative in malignant mesothelioma).3Finally, in considering a diagnosis of primary pulmonary synovial sarcoma, metastases must be excluded. Synovial sarcomas may metastasize to the lung, and a complete examination should be performed to rule out this possibility.