Case 6 -

Pulmonary Synovial Sarcoma Thomas V. Colby, MD Department of Laboratory Medicine and Pathology Mayo Clinic Scottsdale Scottsdale AZ, USA

Clinical History: A 34-year-old man presented at age 30 with a 5.5x4.5x4.0 cm mass in the left lung that was resected. Resection was followed by radiation and chemotherapy with VP16 and cisplatin. Fours years later, at age 34, he was found to have two nodules in the left lung and these were excised and both were similar. Your slide comes from one of these nodules of recurrent neoplasm. Case 6 - Slide 1 Click to view with ImageScope Click to view with a Web-Based Viewer Synovial sarcoma is well described in soft tissues but recognized as a primary tumor in the lung only for the past decade. Most cases are monophasic and prior to the recognition of this tumor most cases were classified as hemangiopericytomas of the lung. Most patients are young to middle age adults with equal sex incidence. The patients may be asymptomatic or have symptoms related to mass effect of the tumor. Prognosis is poor with nearly half the patients dying of their disease. The tumors are typically peripheral and well circumscribed and may attain large size. Involvement of large airways is occasionally encountered. The histopathology is identical to synovial sarcoma of soft tissue with monophasic subtypes being the more common histologic pattern (39 of 40 cases in Begueret series). This is a spindle cell tumor that may have myxoid change, elongated spindle cells, stubby spindle cells, and occasionally epithelial differentiation with glandular spaces. Glandular differentiation should not be confused with entrapment of alveolar spaces, which show TTF positivity of the cells. Immunohistochemically epithelial differentiation can be demonstrated as patchy nests of cells showing pancytokeratin or EMA positivity. Cytokeratin 7 and 19 are said to be particularly useful since other types of sarcomas tend not to express these keratins. Bcl-2 and CD99 are frequently positive. CD34 is usually negative. Desmin is negative; focal reactivity for actin may be noted. In the large French series (see Begueret et al.) 40 cases were defined on the basis of the X:18 translocation and of those 90% expressed at least one epithelial marker. Synovial sarcomas are now redefined on the basis of their genetics with a distinctive translocation that results in the fusion of the SYT gene on chromosome 18 to either the SSX1 or SSX2 gene on chromosome X. In the Begueret series the SSX1 fusion was slightly more common (56.4%) than the SSX2 fusion. The prognosis poor with median 5-year disease free survival being 24 months and 20.9% respectively. The differential diagnosis includes metastatic synovial sarcoma as well as other spindle cell tumors in the lung, including sarcomatoid carcinoma, mesothelioma, thymoma, PPB, localized fibrous tumor, fibrosarcoma, leiomyosarcomas, malignant peripheral nerve sheath tumors, Ewing's sarcoma. References Argani P, Askin FB, Colombani P, Perlman EJ. Occult pulmonary synovial sarcoma confirmed by molecular techniques. Pediatr Dev Pathol. 2000;3:87-90. Begueret H, Galateau-Salle F, Guillou L, Chetaille B, Brambilla E, Vignaudn JM, Terrier P, Groussard O, Coindre JM. Primary intrathoracic synovial sarcoma: a clinicopathologic study of 40 t(X;18)-positive cases from the French Sarcoma Group and the Mesopath Group. Am J Surg Pathol. 2005;29:339-46. Essary LR, Vargas SO, Fletcher CD. Primary pleuropulmonary synovial sarcoma: reappraisal of a recently describedanatomic subset. Cancer. 2002;94:459-69. Hisaoka M, Hashimoto H, Iwamasa T, Ishikawa K, Aoki T. Primary synovial sarcoma of the lung: report of two cases confirmed by molecular detection of SYT-SSX fusion gene transcripts. Histopathology. 1999;34:205-10. Hosono T, Hironaka M, Kobayashi A, Yamasawa H, Bando M, Ohno S, Sohara Y,Sugiyama Y. Primary pulmonary synovial sarcoma confirmed by molecular detection of SYT-SSX1 fusion gene transcripts: a case report and review of the literature. Jpn J Clin Oncol. 2005;35:274-9. Mikami Y, Nakajima M, Hashimoto H, Kuwabara K, Sasao Y, Manabe T. Primary poorly differentiated monophasic synovial sarcoma of the lung. A case report with immunohistochemical and genetic studies. Pathol Res Pract. 2003;199:827-33; discussion 835-6. Terasaki H, Niki T, Hasegawa T, Yamada T, Suzuki K, Kusumoto M, Fujimoto K,Hayabuchi N, Matsuno Y, Shimoda T. Primary synovial sarcoma of the lung: a case report confirmed by moleculardetection of SYT-SSX fusion gene transcripts. Jpn J Clin Oncol. 2001;31:212-6. Travis WD, Brambilla E, Harris CC, Muller-Hemerlink HK, Eds: World Health Organization Classification of Tumours, Pathology and Genetics: Tumours of the Lung, Pleura, Thymus and Heart, IARC, Lyon (2004). Zeren H, Moran CA, Suster S, Fishback NF, Koss MN. Primary pulmonary sarcomas with features of monophasic synovial sarcoma: a clinicopathological, immunohistochemical, and ultrastructural study of 25 cases. Hum Pathol. 1995;26:474-80.