SESSION TITLE: Lung Cancer 3 SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: 10/09/2018 01:15 PM - 02:15 PM INTRODUCTION: Sarcomas are a rare and heterogeneous group of malignant tumors of mesenchymal origin that comprise less than 1% of all adult malignancies [1, 2]. Alveolar soft part sarcoma (ASPS) is a rare tumor that was initially described as a distinctive clinical entity by Christopherson et al. in 1952 [2-3]. It accounts for approximately 0.5–1% of all soft tissue sarcomas and affects mainly adolescents and young adults [4]. We present a case of a patient diagnosed with ASPS, underwent therapy then developed local recurrence. CASE PRESENTATION: 33 year-old male who presented with a chronic cough had a chest x-ray which revealed a paratracheal mass.A follow up computed tomography (CT) scan showed a right paratracheal apical bilobular mass measuring 7.1 cm.The patient underwent a thoracotomy and wedge resection of the upper lobe, which was sent too pathology. Grossly the wedge resection was tan-yellow with areas of hemorrhage.Microscopic examination revealed a TFE3 rearranged nested epithelioid neoplasm with thin vascular fibrous septae with lymphovascular invasion (LVI) consistent with ASPS.Extensive imaging was performed, no metastatic lesions were identified and the patient underwent surgical resection.Postoperatively the patient received radiation therapy due to a positive resection margin.Follow up imaging, nine months post-surgery, revealed multiple masses external to the rib cage consistent with local recurrence.The patient then underwent a second surgical resection and pathology was consistent with ASPS with LVI and positive margins. DISCUSSION: The name “alveolar” was derived from its pseudo alveolar appearance with clustered polygonal cells lacking central cohesion.It is a highly vascular, rare, malignant soft tissue tumor that tends to arise on the extremities of adolescents and young adults.There is a female predilection which is thought to be due to an extra X chromosome [4]. ASPS is associated with t(X;17)(p11;q25) - ASPSCR1/TFE3. The ASPSCR1-TFE3 fusion gene is postulated to be involved in the pathogenesis of this tumor and TFE3 protein expression is sensitive in it diagnosis [5-7].This tumor has a predilection for angioinvasion therefore it is recommended to image the patient for possible metastatic lesions.The 10-year survival after surgical resection of alveolar soft tissue sarcoma is 53.4%,with tumor size and margin status being strong predictive factors [8].ASPS is not sensitive to systemic chemotherapy and the only current available treatment option is Suntinib, a multitargeted Tyrosine Kinase inhibitor[9,10]. CONCLUSIONS: Alveolar soft part sarcoma is a rare malignant tumor with a poor prognosis with a predilection for LVI and distant metastasis. In patients with no metastasis negative surgical margins are a strong prognostic indicator. While surgical resection of ASPS primary and metastatic tumors remains the treatment of choice, optimal adjuvant chemotherapy remains a challenge. Reference #1: 1. Enzinger F M, Weiss S W. Soft tissue tumors. 3rd edn. St Louis: Mosby, 19952. Cancer Statistics, 2017. CA Cancer J Clin. 2017 Jan;67(1):7-30. https://doi.org/10.3322/caac.21387. Epub 2017 Jan 53. Christopherson WM, Foote FW, Jr., Stewart FW. Alveolar soft-part sarcomas; structurally characteristic tumors of uncertain histogenesis. Cancer. 1952;5(1):100–111.4. Weiss SW, Goldblum JR. Enzinger and Weiss’s Soft Tissue Tumors. 5th edition. Philadelphia, Pa, USA: Mosby; 2008.5. The der(17)t(X;17)(p11;q25) of human alveolar soft part sarcoma fuses the TFE3 transcription factor gene to ASPL, a novel gene at 17q25; Oncogene. 2001 Jan 4;20(1):48-576. A proposed explanation for female predominance in alveolar soft part sarcoma. Noninactivation of X; autosome translocation fusion gene?; Cancer. 2005 Mar 15;103(6):1245-53 DISCLOSURES: no disclosure on file for Hashem Ayyad; Advisory Committee Member relationship with Oncocyte Please note: $1001 - $5000 Added 02/26/2018 by Thomas Bauer, source=Web Response, value=Consulting fee No relevant relationships by Anmol Cheema, source=Web Response No relevant relationships by Mohamed Elsawaf, source=Web Response No relevant relationships by shrinil patel, source=Web Response no disclosure on file for Ethan Wasserman