An unusual location of solitary fibrous tumor in heart—A case report and review of literature

Abstract Background Solitary fibrous tumor (SFT) are rare spindle cell tumors originating from the mesenchymal cells mostly from the visceral pleura. SFT was first described as a distinct entity in 1931 by Klemperer et al. Until now, we have limited data regarding the manifestation and behavior of extra pleural forms such as cardiac SFT. Here we present a case of SFT involving the pericardium where the diagnosis was made by imaging followed by biopsy findings. We also review the literature of SFT involving the heart and the management approaches. Case Presentation An 81‐year‐old male presented with progressive dyspnea. Computed tomography (CT) of the chest showed a 6.2 × 5.3 cm soft tissue mass in the anterior mediastinum. Further imaging with CT angiogram showed a stalk‐like connection to the pericardium. A biopsy of the mass showed spindle cells positive for BCL‐2, CD34, and STAT 6, indicative of a solitary fibrous tumor. A surveillance approach was adopted for the patient. Conclusion Primary pericardial tumors are exceedingly rare, with a prevalence rate of 0.001%‐0.007%. Diagnosing a SFT requires a positive CD34 and BCL‐2 marker. The current recommendation is resection of localized disease which has been documented to be curative in cases of benign disease however our patient was put on surveillance.


| INTRODUCTION
Solitary fibrous tumor (SFT) is a rare spindle cell tumor derived from mesenchyme, first described in 1931 by Klemperer et al. originating from the pleura. 1 In 1942, Stout et al., described hemangiopericytomas which was thought to be a vascular neoplasm related to smooth muscle perivascular cells known as pericytes. 2,3 Given the phenotypic and behavioral overlap hemangiopericytoma and SFT were subsequent described to be one tumor type by pathologist. They mostly originate from the pleura however, extra-pleural locations including deep soft tissue, peritoneum, mediastinum, bones, orbit, and parotid glands have been reported. Cardiac SFT are exceedingly rare with limited cases of SFT involving the pericardium documented in the literature. [4][5][6][7][8] Chest radiography, echocardiography, computed tomographic scan (CT scan), positron emission tomography (PET)-CT and magnetic resonance imaging (MRI) are each useful in the diagnosis and origin of the cardiac SFTs. 9 Pericardial and epicardial cases of cardiac SFTs are mostly benign with only four reported malignant Kristen Fain and Kanak Parmar contributed equally to this work. cases. 7,[9][10][11] The best treatment for SFT is surgical resection with a goal of tumor negative surgical margins; however, there is some role for radiotherapy in recurrent SFTs. Chemotherapy is reserved either for metastatic disease or for symptomatic nonresectable SFTs. 7 Here we present a case of SFT involving the heart where the diagnosis was made by imaging followed by biopsy findings. We also review the literature of SFT involving the heart and the management approaches.

| CASE PRESENTATION
A 81-year-old male presented with 4 months of progressively worsening dyspnea on exertion. Medical history was significant for chronic kidney disease (CKD), coronary artery disease status post coronary artery bypass graft (CABG). On presentation, blood pressure was 138/82 mm Hg, heart rate was 76 beats per minute, and a normal respiratory rate.   Electrocardiogram (EKG) was normal. Chest radiography (CXR) revealed a rounded mass measuring 8 cm in the left lower lung lobe ( Figure 1A).
CT scan of the chest without contrast showed an enhancing soft tissue mass along the left aspect of the pericardium, measuring 6.2 Â 5.3 cm ( Figure 1B). At this time, differential diagnosis included pericardial cyst, teratoma, lymphangioma, branchial cyst. CT heart angiogram was ordered and revealed a 6.9 Â 5.4 cm mass in the left inferior mediastinum with a stalk like connection to the pericardium ( Figure 1C).  the cytoplasm, a diameter 10 cm or more than 4 mitoses per 10 highpower fields. 4,9,28 Our case was considered benign based on the lack of mitotic activity and no necrosis. Recent speculation surrounding markers p53 and Ki67 and their ability to predict the malignant potential of SFTs has gained attraction; however, this is not universally accepted at this time. 28 Though these markers are controversial, our patient had a low Ki67 of 3% on the pathology report, which strengthened the prediction for lower malignant potential in our case.
SFTs are most commonly present in adults aged 50-60 years old. In our case given prior history of CABG, tumor location, and patient preference a decision was made to monitor his tumor.
In conclusion, primary pericardial tumors are exceedingly rare, with a prevalence rate of 0.001%-0.007%. 2,12 Diagnosing a SFT requires a multifaceted approach; with IHC and histology being essential for diagnosis. Our case highlights the importance of considering rare diagnosis when working up a mediastinal mass.

INFORMED CONSENT
Written consent from the patient was obtained for the publication of case details and use of images.

FUNDING INFORMATION
No funds were required for the study.