Inclusion body fibromatosis of the shoulder.
DISCUSSIONInclusion body fibromatosis (IBF), also known as infantile digital fibromatosis, is a rare yet benign fibroblastic proliferation. IBF is predominantly encountered in infants and young children with some reports in adults. 1,2 It was first described by Reye in 1965. The precise etiology of IBF remains unknown, although some cases have been reported presenting after previous trauma.Clinically, IBF presents as an asymptomatic, firm, fleshy, dome-shaped nodules, with most cases arising on the dorsal and lateral aspects of fingers and toes. Instances of IBF occurring outside of the digits are exceptionally rare. 3 The characteristic features of IBF include the presence of firm dermal nodules with white-gray cut surfaces located directly beneath the skin and measuring ,2 cm in size. Histologically, IBF is characterized by the proliferation of bland intradermal spindle cells arranged in various patterns within a collagenous matrix. The pathognomonic feature is the presence of paranuclear small, round, pink bodies referred to as inclusion bodies. Masson trichrome stain highlights inclusion bodies. Inclusion bodies count often correlates with lesion age.