Left Atrial Primary Leiomyosarcoma Presenting With Complete Right Pulmonary Vein Thrombosis in a Young Male Patient: A Case Report and Literature Review.

Primary cardiac leiomyosarcomas are extremely uncommon, constituting only a very small fraction of all primary cardiac tumors and a minor subset of cardiac sarcomas. Nearly half occur in the left atrium due to smooth muscle elements in the pulmonary venous junction. Their nonspecific presentation, often mimicking atrial myxoma or thrombus, delays diagnosis and treatment. A 19-year-old male patient presented with recurrent hemoptysis and exertional dyspnea. Initial workup suggested pneumonia; however, contrast-enhanced computed tomography (CT) and echocardiography revealed a large, heterogeneous mass (7.0 × 4.5 × 6.0 cm) filling the left atrium with complete right pulmonary vein thrombosis. Urgent open-heart surgery achieved en bloc tumor excision, posterior left atrial wall reconstruction, right pulmonary vein reimplantation, and valve repairs. Histopathology confirmed an intermediate-grade leiomyosarcoma (French Federation of Cancer Centres grade 2) with spindle cells, necrosis, mild atypia, five mitoses per 10 high-power field, and smooth muscle actin/vimentin positivity. Postoperative CT demonstrated a tumor-free reconstructed atrium and patent pulmonary vein. Complete pulmonary vein thrombosis is a rare but critical indicator of malignant cardiac tumors. While multimodal imaging (echocardiogram, cardiac magnetic resonance imaging, CT, and positron-emission tomography) assesses tumor extent, histology and immunohistochemistry remain diagnostic standards. According to the literature, the prognosis remains poor, and survival rates are low even when surgery is combined with adjuvant chemotherapy. Rare long-term survivors are reported after multimodal treatment. An atrial mass with complete pulmonary vein thrombosis strongly suggests malignancy. Early surgery, histological confirmation, and multidisciplinary care are essential, although prognosis remains poor.