A rare primary pericardial DLBCL masquerading as an unexplained malignant pleural effusion in an elderly woman: A case report.

Introduction: Primary cardiac lymphoma (PCL) is an extremely rare and fatal heart neoplasm. Primary cardiac non-Hodgkin lymphoma (NHL) is uncommon, considering the rarity of pericardial diffuse large B-cell lymphoma (DLBCL) with advanced pleural metastasis. Case presentation: We reported an 86-year-old female with primary pericardial DLBCL diagnosed initially by pleural effusion cytology. The chest imaging study revealed multiple pericardial lobulated infiltrative masses and epicardial invasion. Subsequently, she underwent an emergent pericardial window with a pericardial mass biopsy. The final histopathological and immunohistochemical (IHC) stain confirmed primary pericardial DLBCL, initially showing unexplained malignant pleural effusion. Clinical discussion: The presence and extent of tumour invasion in the heart can be confirmed by echocardiography, computerised tomography (CT), or magnetic resonance imaging (MRI). However, the final histopathological diagnosis requires an examination of the endocardial, myocardial, pericardial window and biopsy or pericardial and pleural effusion cytology. This is the first case report of primary pericardial DLBCL diagnosed by metastatic malignant pleural effusion cytology per the literature review. Conclusion: The definitive diagnosis for primary pericardial DLBCL is based on effusion cytology, histopathological and IHC evaluation, and clinical characteristics and image feature correlation.