Five-year institutional experience with pulmonary artery intimal sarcoma: Two cases highlighting diagnostic challenges and lethal embolic complications

Context Intimal sarcoma is a rare, aggressive malignant mesenchymal neoplasm arising from large vessels and the heart. Pulmonary artery involvement frequently mimics chronic thromboembolic pulmonary hypertension (CTEPH), resulting in delayed diagnosis and poor outcomes. Cases We report two cases of pulmonary artery intimal sarcoma (PAIS) identified in patients undergoing pulmonary endarterectomy for presumed CTEPH. Both patients presented with clinical and radiographic features consistent with chronic thromboembolic disease. Histologic examination of endarterectomy and tumor specimens revealed high-grade sarcomas with predominantly intraluminal growth, marked cytological atypia, and extensive necrosis. Immunohistochemical studies demonstrated limited lineage-specific differentiation, with focal expression of vascular and smooth muscle markers and broad negativity for epithelial, hemato-lymphoid, and melanocytic markers. In both cases, fluorescence in situ hybridization (FISH) demonstrated high-level MDM2 amplification, confirming the diagnosis of intimal sarcoma. Results Despite surgical intervention, both patients experienced rapid postoperative deterioration and died shortly after diagnosis. Conclusion PAIS is an important, but under-recognized mimic of CTEPH. Careful histologic evaluation of pulmonary endarterectomy specimens and consideration of MDM2 FISH testing in atypical cases are critical for accurate diagnosis. These cases underscore the aggressive nature of this entity and the need for heightened pathologic suspicion when thromboembolic disease behaves atypically.