Intravascular Papillary Endothelial Hyperplasia (Masson's Tumor) of the Thumb Presenting as a Giant Cell Tumor of Tendon Sheath: A Case Report and Literature Review.

Masson's tumor, also known as intravascular papillary endothelial hyperplasia (IPEH), is a rare benign vascular lesion of the skin and subcutaneous tissues. It represents the organization and recanalization of a thrombus within a normal vessel, vascular malformation, or hematoma. Although it can occur in any part of the body, its presence in the hand can be particularly challenging to differentiate from other soft-tissue lesions. We present a case of Masson's tumor located in the distal phalanx of the thumb. Initial magnetic resonance imaging (MRI) examination suggested a giant cell tumor of the tendon sheath; however, following surgical excision, histopathological evaluation confirmed the diagnosis of Masson's tumor. This case highlights the critical importance of histopathological examination, as Masson's tumor can closely mimic other soft-tissue lesions.