Masson Tumour - A Rare Cause of a Hand Lump.

Intravascular papillary endothelial hyperplasia, also known as Masson tumour, is a rare proliferative vascular lesion that can affect the hand. We report a patient who was operated on for a progressively enlarging soft tissue lump at the base of his thumb. Initially, it was thought to be a post-traumatic false aneurysm arising from a branch of the radial artery following blunt trauma. Subsequent histology revealed it to be a Masson tumour. We aim to highlight this rare pathology that can affect the hand and the diagnostic confusion we faced during the evaluation and management of this patient. Level of Evidence: Level V (Therapeutic).