Spectrum of Histological Features in Infantile Digital Fibromatosis

Abstract

Infantile digital fibromatosis (IDF), also called Reye tumor or inclusion body fibromatosis, is a benign proliferation of myofibroblasts, with characteristic perinuclear eosinophilic cytoplasmic inclusion bodies. The inclusions stain pink with hematoxylin‐eosin, red with Masson’s trichrome, and purple with phosphotungstic acid‐hematoxylin. This intradermal neoplasm is formed by interlacing bundles of collagen and spindle cells. Positive immunohistochemical staining with vimentin, cytokeratin, desmin, and actin indicate myofibroblastic cell origin. Clinically, patients present at birth or infancy with asymptomatic smooth, flesh colored nodules, typically on lateral or dorsal digits. IDF is a benign neoplasm that may spontaneously regress and treatment is observation. Lesions recur in 60% of excisions; surgery is only recommended in cases of functional impairment or aggressive growth. We report three cases of IDF. The patients, ranging 8 months to 8 years old, presented with pink to flesh colored nodules on the feet and fingers. A spectrum of histological features was observed. All cases revealed dermal proliferation of spindle cells with blunt nuclei and eosinophilic intracytoplasmic inclusions. Pattern of spindle cells ranged from loose haphazard arrangement to well‐organized interlacing bundles. The quantity of eosinophilic inclusions varied. For diagnostic and treatment purposes, all three patients underwent excision, with subsequent recurrence in two cases.