Primary Pericardial Synovial Sarcoma: A Case Series and Review of Literature

Abstract

Primary pericardial synovial sarcoma (PPSS) is a rare and aggressive cancer that arises from pluripotent mesenchymal cells of the pericardium. The pathognomonic genetic hallmark is the chromosomal translocation t(X;18)(p11;q11), resulting in the SS18-SSX fusion oncogene, which, down the line, disrupts transcription regulation and chromatin remodeling, ultimately leading to carcinogenesis. In our article, we describe two cases of PPSS in previously healthy young men, managed with multidisciplinary teams, along with a review of the literature of cases reported to date. Both of our patients are young adults, with very different presentations in terms of symptoms, one presenting with shortness of breath (SOB) and the second with chest pain. Both patients had imaging studies that reported a pericardial mass. Ultimately, a diagnostic evaluation was done, with fluorescence in situ hybridization (FISH) confirming primary pericardial synovial sarcoma. Unfortunately, both patients passed away within a week of diagnosis. A comprehensive search of public databases, including PubMed and Google Scholar, was conducted up to 2025. The search criteria included synovial pericardial sarcoma, sarcoma of the heart, cardiac sarcoma, and primary pericardial synovial sarcoma. The search yielded over 100 results, of which 46 articles focused specifically on primary pericardial synovial sarcoma. This article summarizes all reported PPSS cases to date, including patient age, race, gender, symptoms, cytological analysis, and histological subtypes.

Keywords: cardiac tumors; pericardial sarcoma; primary pericardial sarcoma; spindle cell sarcoma; thoracic oncology.

Figure 1. (A) Radiograph of the chest (PA view) with cardiomegaly (black arrows in A) and right small pleural effusion (blue arrow in A). (B) Bedside echocardiogram with large posterior pericardial mass (orange arrows in B).

PA: posteroanterior

Figure 2. (A) Axial CECT of the lower chest demonstrating a large pericardial mass (yellow arrows in A), encasing the IVC (green arrow in A), with moderate-sized right pleural effusion (red arrow in A). (B) Coronal CECT of the chest demonstrating a large pericardial mass (yellow arrows in B), encasing the ascending aorta (red arrow in B). (C) Axial CECT of the upper chest demonstrating a pericardial mass (yellow arrow in C), encasing the right (red arrow in C) and left (green arrow in C) pulmonary arteries. (D) Axial CECT of the mid chest demonstrating a large pericardial mass (yellow arrow in D), encasing the right inferior (red arrow in D) and left inferior (green arrow in D) pulmonary veins. (E) Axial CECT of the upper abdomen demonstrating reflux of contrast into the hepatic veins (red arrow in E) and right pleural effusion (orange arrow in E). (F) CT-guided biopsy (green arrow in F) of pericardial mass (yellow arrow in F).

CECT: contrast-enhanced computed tomography, IVC: inferior vena cava, CT: computed tomography

Figure 3. (A) H&E stain of a representative section of the pericardial tumor at 20× magnification showing viable tumor, hyalinization, and hemosiderin-laden macrophages, consistent with treatment effect. (B) H&E stain of a representative section of the pericardial tumor at 200× magnification showing delicate, uniform, and relatively small spindle cells, arranged in dense cellular sheets or vague fascicles, with sparse cytoplasm and ovoid, hyperchromatic nuclei with regular granular chromatin, high N:C ratio, and inconspicuous nucleoli. (C) H&E stain of a representative section of the pericardial tumor at 20× magnification showing tumor necrosis, hyalinization, and viable tumor. (D) SS18-SSX immunostain demonstrating positive expression in viable tumor cells.

H&E: hematoxylin and eosin

Figure 4. (A) Axial T2W MRI of the lower chest with a large pericardial mass appearing T2 hypointense (yellow arrow), with few areas of moderate T2 hyperintensity (green arrow). (B) Axial T1W post-contrast MRI of the lower chest with hypoenhancing mass (red arrow), with few areas of heterogeneous enhancement (orange arrow).

T2W: T2-weighted, MRI: magnetic resonance imaging, T1W: T1-weighted

Figure 5. (A) Axial CECT of the chest with a decrease in the size of the pericardial mass (yellow arrows). (B) Coronal CECT of the chest with a decrease in the size of the pericardial mass (orange arrows).

CECT: contrast-enhanced computed tomography

Figure 6. (A) Chest radiograph (PA view) with enlarged cardiac silhouette (black arrows in A). (B) Axial CECT of the lower chest with a large heterogeneously enhancing necrotic mass along the posterior inferior aspect of the heart, originating from the pericardium (red arrows in B). (C) Coronal CECT of the chest with a large pericardial mass (red arrows in C) infiltrating into the right atrium and right ventricle (yellow arrow in C). (D) Axial CECT of the mid chest with the partially visualized pericardial mass (red arrow in D), completely encasing the proximal left circumflex coronary artery (yellow arrow in D). The mid and distal left circumflex coronary artery (not seen in this section) was completely obliterated.

PA: posteroanterior, CECT: contrast-enhanced computed tomography

Figure 7. (A) 18F-FDG PET/CT scan with intense tracer uptake in this mass (black arrow in A). (B) Coronal T2W MRI of the chest without contrast with a large heterogeneous pericardial mass (red arrows in B), extending into the right atrium (yellow arrow in B). (C) Axial T2W MRI of the lower chest with heterogeneous pericardial mass (red arrows in C). Significant compromise of cardiac function was noted.

18F-FDG PET/CT: fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography, T2W: T2-weighted, MRI: magnetic resonance imaging