Post-Traumatic Intravascular Papillary Endothelial Hyperplasia (Masson Tumor) of the Eyelid.

Intravascular papillary endothelial hyperplasia (IPEH), also known as Masson tumor, is a rare benign vascular lesion characterized by reactive endothelial proliferation within the vessel lumen. Eyelid involvement is exceedingly uncommon and may clinically mimic malignant vascular tumors. The authors report a case of post-traumatic IPEH of the eyelid in a 50-year-old man presenting with a slowly enlarging purplish nodule in the lateral canthal region. Complete surgical excision was performed. Histopathologic examination revealed tuft-like papillary endothelial proliferation confined within an expanded vein with associated thrombus, without cytologic atypia or mitotic activity, consistent with the pure type of IPEH. Immunohistochemical staining showed diffuse CD34 positivity and negative p53 expression, supporting the diagnosis and excluding angiosarcoma. No recurrence was observed during follow-up. This case underscores the extreme rarity of eyelid involvement and emphasizes that, despite a history of trauma, accurate subtype classification of IPEH relies on histopathologic rather than clinical findings.