Histopathologic study of Koenen tumors. Are they different from acquired digital fibrokeratoma?

Fifteen periungual fibromas from nine patients were studied histologically. The lesions were elongated. Capillaries were found in the distal part surrounded by thin collagen bundles whereas the proximal part was made up of dense, closely packed fibers. The epidermis covering the tumor appeared to be connected with the nail fold. The dense collagen of the lesion faded into the normal structure of the cutis of the proximal nail fold. Periungual fibromas can be subdivided into (1) fibrokeratomas originating from the dermal connective tissue and (2) fibrokeratomas originating from the proximal nail fold.