Answer:
Presents as a symmetrical hemispheric growth on the dorsum of the wrist, most frequently between the base of the second or third metacarpal and the trapezoid or capitate. This tumor is believed to be due to a congenital accessory ossification center resulting in maldevelopment of the joint. Predisposed to degenerative arthritis. If symptomatic, rongeur the bony lip to flatten and smooth the dorsal surface.