PULMONARY ARTERY INTIMAL SARCOMA MISTAKEN FOR AN ACUTE PULMONARY EMBOLISM

Abstract

SESSION TITLE: Fellows Lung Pathology Posters SESSION TYPE: Fellow Case Report Posters PRESENTED ON: October 18-21, 2020 INTRODUCTION: Pulmonary artery intimal sarcoma (ISPA) is an exceedingly rare tumor that arises from the vascular lumen of the pulmonary artery (PA). We present a patient who was initially thought to have an acute pulmonary embolism (PE) and later diagnosed with ISPA. CASE PRESENTATION: A 23-year-old woman initially presented to an outside hospital 6 months prior with progressive dyspnea. Imaging reportedly showed an acute PE in the right main PA and the patient was discharged on anticoagulation. Her symptoms worsened. Repeat imaging revealed a large 8.9 cm right hilar mass as well as a large filling defect extending from a stenosed right main PA, across the pulmonary trunk, into left lower lobe PA (Fig 1 A-C). The soft-tissue density and nodular appearance of the defect was more fitting with tumor than recurrent or chronic PE. Positron-emission tomography (PET) showed the right hilar mass was highly FDG avid and the vascular lesion mildly FDG avid, consistent with malignancy (Fig 1 D). The patient underwent percutaneous biopsy of the mass. Histopathology revealed a poorly differentiated sarcoma. FISH studies were positive for MDM2 (murine double minute 2). Together these findings were consistent with ISPA. The patient was started on chemotherapy with doxorubicin, ifosfamide, and mensa. Restage Imaging after 4 of 6 cycles showed a significant response to therapy (Fig 2), with the plan for surgical reconstruction with endarterectomy. DISCUSSION: Pulmonary artery sarcomas are an extremely rare malignancy, with an estimated incidence of 0.001-0.03% and only 200-400 cases described, the majority post-mortem. There appears to be a slight female predominance (1.3:1) with a mean age of diagnosis of 48 years (13-86 years). These tumors arise in the pulmonary trunk, either in the intimal (ISPA) or mural layer, and extend locally along the vasculature into the adjacent structures. The majority of patients present with symptoms of PE or right heart failure and are initially misdiagnosed. Diagnosis requires tissue biopsy. Histopathology often shows poorly differentiated, malignant spindle or epithelioid cells with atypia. Immunohistochemical staining is variable, sometimes with desmin or smooth muscle actin positivity. MDM2 is a proto-oncogene that regulates p53 activity and is highly expressed in the majority of ISPA. Surgical resection with endarterectomy is considered first line and confers a modest survival benefit (10 vs 1.5 months, compared to no surgery). Neoadjuvant chemotherapy improves surgical outcomes and survival, however due to its rarity, there is no consensus treatment and data is extrapolated from extrapulmonary sarcomas, often using doxorubicin-based regimens. CONCLUSIONS: ISPA is an incredibly rare malignancy that is often misdiagnosed a PE and carries an overall grim prognosis. Reference #1: Mussot S, et al. Retrospective institutional study of 31 patients treated for pulmonary artery sarcoma. Eur J Cardiothorac Surg. 2013 Apr;43(4):787-93. PMID 22843511 Reference #2: Assi T, et al. A comprehensive review of the diagnosis and management of intimal sarcoma of the pulmonary artery. Crit Rev Onc. 2020 Jan;147: 1040. Reference #3: Blackmon SH, et al. Management of primary pulmonary artery sarcoma. Ann Thorac Surg. 2009 87(3):977-984. DISCLOSURES: Speaker/Speaker's Bureau relationship with Boehringer-Ingelheim Pharmaceuticals Please note: $5001 - $20000 Added 04/07/2020 by Jaime Betancourt, source=Web Response, value=Honoraria Speaker/Speaker's Bureau relationship with Vapotherm, Inc Please note: $5001 - $20000 Added 04/07/2020 by Jaime Betancourt, source=Web Response, value=Honoraria No relevant relationships by Richard Watson, source=Web Response