Cytological Diagnosis of Primary Cardiac Angiosarcoma Presenting With Multiple Serous Effusions: A Case Report With Cell Block.

Primary cardiac angiosarcoma (PCAS) is the most aggressive primary malignant cardiac tumor. Owing to the nonspecific nature of clinical symptoms, early detection, diagnosis, and treatment remain challenging. The tumor is characterized by high malignancy, a propensity for early metastasis, and an overall poor prognosis. We report a 42-year-old female presenting with abdominal distension and exertional dyspnea for 1 month, found to have a cardiac space-occupying lesion and multiple serous effusions on imaging. The final diagnosis of PCAS was established by combining cytomorphological analysis of the pleural effusion (showing pleomorphic tumor cells with marked atypia), cell block (CB) preparation, and immunocytochemical (ICC) staining. Next-generation sequencing (NGS) of the CB specimen identified a missense mutation in MSH2 (c.14C>A, p.Pro5Gln) with a variant allele frequency (VAF) of 48%, confirming the feasibility of CB as an alternative specimen for molecular testing. The patient received chemotherapy combined with radiotherapy and remained in stable clinical condition. Cytopathology offers a valuable diagnostic approach for patients with primary cardiac tumors in whom histological sampling cannot be obtained, and molecular testing using CB specimens can provide additional insights into the genetic profile of such rare tumors.