A case report of malignant primary pericardial mesothelioma with atypical imaging appearance: multimodality imaging with histopathological correlation.

Background: Primary pericardial mesothelioma is a rare primary cardiac malignancy, with three main histopathological types, sarcomatoid histotype being the rarest. The imaging features were atypical due to concomitant extensive calcification, which resulted in aggravated differential diagnosis.

Case Summary: A 45-year-old man presented to our hospital with non-specific clinical symptoms. According to clinical history, a mediastinal tumour had been suspected with a previous unsuccessful attempt of transthoracic computed tomography-guided biopsy at an overseas hospital with limited data of performed imaging procedures. Multimodality imaging at our centre revealed extensively calcified solid masses in the pericardium, invading the left atrium. As the imaging features suggested an atypical primary pericardial malignancy, a diagnostic thoracoscopy was performed. Histopathological analysis of specimen revealed sarcomatoid type of pericardial mesothelioma with areas of necrosis and foci of osteogenic differentiation. Despite planned treatment, 2 weeks after histological diagnosis, the patient passed away due to perforated peptic ulcer-related sepsis.

Discussion: The presence of extensive calcification in the lesion resulted in a challenging imaging workup and diagnosis. Initial differential diagnosis included primary or metastatic calcification-prone tumour, secondary calcification due to haemorrhage after previous interventional procedure and other pathologies, such as tuberculous pericarditis, calcified amorphous tumour, among others. Calcification may be part of the histological tumour characteristics; however, proper history taking is crucial as concomitant diseases, previous treatment, and interventional procedures may alter the imaging pattern.