Case Report: Three rare cases of pseudomyogenic hemangioendothelioma with atypical skeletal involvement.

Introduction: Pseudomyogenic hemangioendothelioma (PHE) is a rare vascular neoplasm of intermediate malignant potential that predominantly affects young adult men and most frequently arises in the lower extremities. Involvement of unusual skeletal sites is uncommon, and the nonspecific imaging features of PHE may contribute to diagnostic uncertainty. Case report: We report three cases of PHE involving unusual osseous locations, including the thoracic spine, femur, and humerus, with one case showing concomitant soft tissue involvement of the upper arm. Multimodal imaging, including computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography/computed tomography (PET/CT), demonstrated osteolytic bone destruction, soft tissue extension, heterogeneous enhancement, and increased metabolic activity. All patients underwent individualized surgical management according to tumor location and disease extent. The final diagnosis was established by histopathological and immunohistochemical (IHC) evaluation, particularly FOSB positivity and endothelial marker expression. Conclusion: PHE should be considered in the differential diagnosis of atypical bone and soft tissue lesions, even when they occur at uncommon anatomic sites or in patients outside the typical demographic profile. Comprehensive imaging assessment, histopathological confirmation, individualized treatment, and long-term follow-up are essential for accurate diagnosis and optimal clinical management.