Trends in the Incidence of Rare Primary Cardiac Neoplasms: A Surveillance, Epidemiology, and End Results (SEER)-Based Analysis.

Background Primary malignant cardiac tumors (PMCTs) are considered extremely rare neoplasms, with limited population-level data on incidence patterns and future trends. This study aims to describe the epidemiology of PMCTs in the United States, focusing on three main histologic subtypes, such as sarcomas, lymphomas, and mesotheliomas, and to forecast incidence over the next decade. Methods We extracted cases of pathologically confirmed PMCTs diagnosed between 2000 and 2022 from the Surveillance, Epidemiology, and End Results (SEER) 17 Registries database. Incidence rates (IRs) were age-adjusted to the 2000 US Standard Population and stratified by histology, sex, age (<60 vs. ≥60 years), and race. Annual percent change and percentage change were calculated. Time series forecasting was performed using linear regression, ETS, ARIMA, and neural network autoregression models, with model selection based on root mean square error, mean absolute error, mean absolute percentage error, and residual diagnostics. Poisson and quasi-Poisson regression analyses evaluated demographic associations with incidence. Results From 2000 to 2022, PMCTs demonstrated distinct subtype-specific trends. Cardiac lymphoma incidence increased steadily, with forecasts predicting a rise from 0.062 per 100,000 in 2023 to 0.080 by 2032. Sarcoma incidence remained stable (~0.008-0.009 per 100,000) but was highly volatile year to year. Mesothelioma incidence was consistently low (<0.001 per 100,000) but projected to increase slightly over time. Age ≥60 years was strongly associated with higher sarcoma and mesothelioma incidence, whereas lymphoma showed no significant age-related difference. Sex and race disparities were evident: males had higher sarcoma and mesothelioma rates, while females had slightly higher lymphoma rates; Asian/Pacific Islander groups exhibited greater volatility in lymphoma incidence, and Black populations had the lowest incidence across subtypes. Conclusions PMCTs remain exceptionally rare, but incidence trends vary by histologic subtype. Cardiac lymphoma incidence is rising and expected to continue increasing, whereas sarcoma rates are stable, and mesotheliomas show a modest upward trajectory. These findings highlight the need for improved detection in high-risk groups, the integration of molecular data into registries, and the development of global cardiac tumor collaborations to refine epidemiologic understanding and improve patient care..