Rare Primary Pericardial Mesothelioma on an [18F]FDG PET/CT Scan and Its Postchemotherapy Response Evaluation

Introduction

Primary cardiac tumors of the heart are uncommon, whereas primary pericardial mesothelioma (PPM) is exceptionally rare, with an incidence of only 0.0022% in a series of nearly 500,000 random autopsies and constituting about 6% of all mesotheliomas.[12] The optimal treatment for PPM has not been well established. Owing to the poor response to existing systemic and radiation therapy, radical surgery remains the cornerstone of treatment in an attempt to cure the localized disease. The diagnosis of PPM is usually difficult and late, and in the majority of cases, the diagnosis of PPM is typically made at autopsy.[3] The majority of the cases have common clinical features, including constrictive pericarditis, cardiac tamponade, and cardiac failure. The majority of the reported pericardial malignancies are metastatic in nature, with a poor prognosis.[4]

Case Report

The patient is a 65-year-old female who presented with complaints of shortness of breath (NYHA grade III) with occasional orthopnea and chest pain for the past 3 months.

Discussion

There was no other significant medical or surgical history. Her chest radiogram shows cardiomegaly [Figure 1]. A 12-lead echocardiography was done, which revealed moderate pericardial effusion with associated pericardial thickening. Following this, a nonintravenous contrast computed tomography (CT) chest was done, which also demonstrated moderate pericardial effusion and associated plaque-like calcification with supraclavicular and mediastinal lymphadenopathy. Pericardial tapping was done to relieve the symptoms and also for cytology, which showed atypical malignant cells. The patient was further referred to the department of nuclear medicine and positron emission tomography with CT (PET/CT) to look for the primary and metastatic disease as well as also for the prompt site of biopsy. An 18F-fluorodeoxyglucose PET/CT (FDG PET/CT) scan [Figure 2] was performed with all preparations, which revealed mild residual pericardial effusion with metabolically active pathological diffuse plaque-like and nodular pericardial thickening indenting the right ventricle with a maximum thickness of about 1.5 cm along the right atrium with the maximum standardized uptake value (SUVmax) 21.9 [Figure 2], and associated mild plaque-like pericardial calcification was also seen predominantly overlying the right-sided chambers with passive atelectatic changes seen in the adjacent lungs bilaterally. There are multiple metabolically active inhomogeneously enhancing small and mildly enlarged mediastinal lymph nodes seen in prevascular, pre and paratracheal, subcarinal, paracardiac, bilateral hilar, and epiphrenic regions, with foci of calcification also seen in the subcarinal nodes with one of the larger right paracardiac lymph nodes was measured about 2.2 cm × 0.9 cm with SUVmax 9.9 [Figure 3]. A few small subcentimeter-sized metabolically active left supraclavicular (SUVmax 4.2) and gastrohepatic (SUVmax 5.7) nodes are also seen. There is no additional hypermetabolic lesion noted elsewhere in the body. Thus, a primary pericardial malignancy was suspected based on the imaging results.

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Figure 1 (a) The initial chest radiogram shows cardiomegaly with pericardial effusion (white arrow), (b) The follow-up posttherapy chest radiogram after eight cycles of chemotherapy reveals reversal of cardiomegaly with complete resolution of pericardial effusion (white arrow)

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Figure 2 (a and b) Postchemotherapy and Prechemotherapy therapy 18F-fluorodeoxyglucose positron emission tomography with computed tomography scan MIP images showing significant resolution of metabolic activity in pericardial disease (red arrows), (c) Postchemotherapy 18F-fluorodeoxyglucose positron emission tomography with computed tomography scan revealed regression in size and metabolic activity of the pericardial thickening with complete resolution of pericardial effusion (blue arrow), (d) Prechemotherapy 18F-fluorodeoxyglucose positron emission tomography with computed tomography scan shows metabolically active pericardial thickening (white arrow) and pericardial effusion (blue arrow)

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Figure 3 (a) Postchemotherapy images of computed tomography and fused 18F-fluorodeoxyglucose positron emission tomography with computed tomography scan revealed significant regression in size with complete resolution in metabolic activity of metastatic mediastinal right paracardiac node (blue circle), (b) Prechemotherapy axial images of computed tomography and fused 18F-fluorodeoxyglucose positron emission tomography with computed tomography scan revealed metabolically active inhomogeneously enhancing metastatic enlarged right paracardiac lymph node (blue circle)

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A CT-guided biopsy was performed from the targeted area, and microscopic examination of H and E stain revealed abundant pleomorphic malignant mesothelioma cells predominantly of epitheloid type [Figure 4]. Immunohistochemical staining was positive for vimentin, calretinin, CK7, and D2-40 (podoplanin) and negative for CEA, TTF-1, PLAP, CD30, and CD117.[5] Because the pericardium was the only lesion visible on the FDG PET/CT scan and there was no evidence of primary cancer origin in other organs, the patient was finally diagnosed with primary malignant pericardial mesothelioma. The patient had taken eight cycles of combination chemotherapy with Bevacizumab 400 mg and carboplatin 450 mg. The relief of symptoms was observed after two cycles. After chemotherapy, a repeat chest radiograph [Figure 1] and an FDG PET/CT scan [Figure 2] were done after 7 months, which showed significant resolution in size and metabolic activity of the pericardial thickening with a mild residual area along the right atrium with a maximum thickness of 4–5 mm and SUVmax 5 [Figure 2]. The complete resolution of pericardial effusion as well as significant regression in size and number with complete resolution in metabolic activity of associated lymphadenopathy [Figure 3], was noted with no new lesion. The patient underwent a complete pericardiectomy and exploration through sternotomy to search for residual malignant tissue. There were no intraoperative and postoperative complications, and advised four more cycles of the same chemotherapy regimen. The patient is still alive after 12 months and is currently on regular follow-up and conservation management.

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Figure 4 Microscopic examination on H and E stain revealed abundant pleomorphic malignant mesothelioma cells predominantly of epitheloid type (black arrow)

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Conclusion

Primary pericardial mesotheliomas are an extremely rare malignancy of unknown etiology. The onset of symptoms is usually insidious and has a progressive clinical course and grave prognosis with constrictive pericarditis or pericardial effusion with or without cardiac tamponade and heart failure caused by myocardial infiltration. As a whole-body scan modality, 18F-FDG PET/CT has a promising role in accurate diagnosis and staging, as well as helping in targeting the biopsy site, postchemotherapy response evaluation, and surgical planning. The PPM was, although rarely reported, in the Indian population.