Guan T, et al. - Researchers sought to determine how tumor size affects overall survival and cancer-specific survival of primary cardiac sarcoma (PCS) patients in order to present a reference for the surgical treatment. The SEER database yielded data of 261 PCS patients from 1983 to 2016, for inclusion. The tumor size was classified into two subgroups—less than or equal to 4.0 cm (≤ 4.0 cm) and greater than 4.0 cm (> 4.0 cm)—using the X-tile program. Outcomes revealed an independent predictive value of tumor size of > 4.0 cm for poor prognosis and its association with the surgical outcome in PCS patients. PCS patients with tumor size > 4.0 cm had significant improvement in the prognosis following surgery. Based on the findings, clinicians may better evaluate the prognosis of PCS patients and develop optimal therapeutic strategies.