Supplementary Material for: The Pleural origin of Retiform Hemangioendothelioma: an unusual origin of a rare diagnosis

Introduction: Vascular malignancies are categorized into benign hemangiomas, malignant angiosarcomas, and tumors of intermediate malignancy. Retiform Hemangioendothelioma (RH) is one of the rare diagnoses belonging to the class of intermediate malignancies that was initially diagnosed. Case Presentation: In this case report, we have reported a rare case of Retiform Hemangioendothelioma, a locally aggressive, vascular tumor of malignant potential presenting at an unusual site. The most observed locations of this soft tissue tumor are skin and Subcutaneous tissues of extremities; however, this case of Retiform Hemangioendothelioma was observed in an unusual site called pleura, which is a rare occurrence related to this tumor. The presence of cell surface markers like CD31 and ERG of Vascular and endothelial origin and the presence of hobnail appearance of endothelial channels on the biopsy profile supported the vascular origin of the tumor; the clinical features and Imaging studies further confirmed the diagnosis of RH. Conclusion: In this case report, a rare case of Retiform Hemangioendothelioma with an unusual site of origin was highlighted. Retiform Hemangioendothelioma is a vascular neoplasm commonly observed sites of this vascular tumor were skin and subcutaneous tissue of the extremities, however, in this case, the site was unusually different which was the pleura of the left lung.