Abstract. Pulmonary artery (PA) leiomyosarcoma (PAL) is a rare but extremely malignant tumor of the cardiovascular system, which is often misdiagnosed as pulmonary thromboembolism. Although the early detection and surgical resection improves patient survival, the benefits of adjuvant therapy are not well understood. The current study presents the case of a patient with primary PAL who underwent surgical resection along with three courses of chemotherapy. Despite these interventions, the patient experienced recurrence of the PAL within four months following treatment. The patient received localized radiotherapy and subsequently achieved a stable disease state. This case indicates that radiotherapy may offer a benefit to PAL patients, particularly those who do not respond to chemotherapy.