Open Access Maced J Med Sci. 2021 Jul 14; 9(C):109-113. 109 Scientifc Foundation SPIROSKI, Skopje, Republic of Macedonia Open Access Macedonian Journal of Medical Sciences. 2021 Jul 14; 9(C):109-113. https://doi.org/10.3889/oamjms.2021.6541 eISSN: 1857-9655 Category: C - Case Reports Section: Case Report in Surgery Monophasic Synovial Sarcoma of the Left Ventricle of the Heart: An Extremely Rare Case and Literature Review Anindhita Muthmaina 1 , Ery Kus Dwianingsih 2 * , Shinta Andi Sarasati 2 , Hendry Purnasidha Bagaswoto 1 , Hasanah Mumpuni 1 1 Departement of Cardiology and Vascular Medicine, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada, Dr. Sardjito General Hospital, Yogyakarta, Indonesia; 2 Department of Anatomical Pathology, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada, Dr. Sardjito General Hospital, Yogyakarta, Indonesia Abstract BACKGROUND: Cardiac sarcomas account for <25% of all cardiac tumors. Of these, angiosarcomas are the most frequent. Synovial sarcomas (SS) are exceedingly rare. We present a case of primary left ventricle (LV) SS, a form of sarcoma particularly rare in the heart. CASE DESCRIPTION: A 19-year-old male was referred for further investigation of a LV tumor, presented with a 3-month history of exertional dyspnea and palpitations. He also experienced several syncopal episodes. The radiologic examination confrmed a mass in the LV, suspected for myxoma of the LV. Histopathologic examination revealed a malignant tumor with spindle cell components, suggesting leiomyosarcoma with diferential diagnosis of monophasic SS. Immunohistochemistry demonstrated reactivity of the spindle cell component with the mesenchymal marker vimentin and BCL2 protein, while the smooth muscle marker, desmin, was negative, confrming the diagnosis of monophasic SS. CONCLUSIONS: Monophasic SS in the heart is diagnostically challenging since it shares the broad list of diferential diagnoses of spindle cell tumors. Immunostaining is helpful to diferentiate those entities to obtain a defnitive diagnosis and proper treatment. Edited by: Sinisa Stojanoski Citation: Muthmaina A, Dwianingsih EK, Sarasati SA, Bagaswoto HP, Mumpuni H. Monophasic Synovial Sarcoma of the Left Ventricle of the Heart: An Extremely Rare Case and Literature Review. Open Access Maced J Med Sci. 2021 Jul 14; 9(C):109-113. https://doi.org/10.3889/oamjms.2021.6541 Keywords: Sarcoma; Synovial sarcoma; Primary tumor; Heart *Correspondence: Ery Kus Dwianingsih, Department of Anatomical Pathology, Faculty of Medicine, Public Health and Nursing, Universitas Gadjah Mada/Dr. Sardjito General Hospital, Yogyakarta, Indonesia. E-mail: ery_malueka@ugm.ac.id Received: 29-May-2021 Revised: 21-Jun-2021 Accepted: 23-Jun-2021 Copyright: © 2021 Anindhita Muthmaina, Ery Kus Dwianingsih, Shinta Andi Sarasati, Hendry Purnasidha Bagaswoto, Hasanah Mumpuni Funding: This research did not receive any fnancial support Competing Interests: The authors have declared that no competing interests exist Open Access: This is an open-access article distributed under the terms of the Creative Commons Attribution- NonCommercial 4.0 International License (CC BY-NC 4.0) Introduction Primary cardiac tumors are very rare, and most of them are benign. Malignant primary cardiac tumor only represents 25% of all primary cardiac tumors, and most of them are sarcomas [1]. Undiferentiated sarcoma is the most common type of sarcoma in the heart, followed by angiosarcoma (25%), leiomyosarcoma (25%), and synovial sarcoma (SS) [2]. In another study, angiosarcoma was found as the most frequent sarcoma, followed by malignant fbrous histiocytoma, leiomyosarcoma, and SS. Cases with SS only account for 2% of the sarcomas in the heart [2], [3]. Primary cardiac sarcomas are predominantly located in the heart’s right side, with the right to left side ratio of 2:1 [4]. In this case, we report the left ventricle’s (LVs) primary cardiac SS, with a chief complaint of syncope. The diagnosis was confrmed by histopathological analysis and immunostaining. Case Description A 19-year-old male patient was suddenly unconscious when he was working 3 weeks prior to hospital admission. Palpitation or chest pain was not reported prior to unconsciousness event. Initially, the patient did not seek for medical help, however, a week later the symptom was repeated. He went to a private hospital, and congenital heart disease was suspected. An echocardiographic examination was performed and revealed a mass at the LV. He was referred to Dr. Sardjito General Hospital with the diagnosis of suspected LV Myxoma. Physical examination showed a 2/6 pan systolic murmur in the apex. Transthoracic and transoesophageal echocardiography examinations were performed, and showed two LV masses: one sized 2.6 cm × 1.5 cm attached to the posterior mitral left, and another, sized 1.2 cm × 2.1 cm with peduncle attached to the anterior mitral leafet that obstructed the LV outfow tract (LVOT) (Figures 1 and 2). A Cardiac