An Elusive Intracardiac Mass: Diagnosing Intimal Sarcoma of the Heart

Background: Primary cardiac tumors are rare, with an incidence of 0.002% to 0.03% in autopsy series, and <25% are malignant.Primary cardiac intimal sarcoma is an exceptionally aggressive subtype arising from the endocardial intimal layer, histologically characterized by malignant spindle cells and frequently associated with MDM2 overexpression.The nonspecific presentation, rapid progression, and limited therapeutic options contribute to the poor prognosis for patients with intimal sarcoma.Case Report: A 54-year-old female presented with progressive exertional dyspnea, chest discomfort, and palpitations.Transthoracic echocardiography revealed a mobile 3.6 × 2.8-cm mass involving the anterior mitral leaflet and causing severe functional mitral stenosis (mean gradient 18 mm Hg).Computed tomography demonstrated a filling defect in the left inferior pulmonary vein and mediastinal lymphadenopathy without distant metastases.The patient underwent surgical excision and bioprosthetic mitral valve replacement.Histopathology confirmed intimal sarcoma with a high proliferative index (Ki-67 40% to 50%) and supportive immunohistochemical features.Postoperative imaging showed residual tumor and a mitral valve pseudoaneurysm, prompting repeat surgery with cardiac autotransplantation, extensive tumor resection, left atrial reconstruction, and mitral valve replacement.The patient received multimodal therapy that included anthracycline-based chemotherapy and enrollment in a clinical trial with the MDM2 inhibitor brigimadlin.Following a brief period of disease stability during treatment with brigimadlin, the patient's disease progressed and she died.Conclusion: Primary cardiac intimal sarcoma is a rare, highly malignant tumor with poor outcomes despite aggressive multimodal therapy.Surgical resection is the cornerstone of management for symptom relief and local control, while emerging therapies may offer disease stabilization in select patients.