Reports of IDF developing in older children and adults are rare. Patients are asymptomatic, without associated systemic symptoms. They can grow to 2 centimeters in size, yet rarely cause functional impairment or deformity. Distribution of lesions includes fingers and toes with equal frequency, except for sparing of the thumbs and great toes. Rare extradigital sites reported include hands, feet, arms, nose, breast, and tongue.
Skin biopsy is recommended to confirm the diagnosis.
Interlacing fascicles of spindle-shaped cells and collagen bundles form a dermal nodule. The nodule may extend into the subcutaneous tissue. The ovoid nuclei of the cells are accompanied by characteristic perinuclear eosinophilic cytoplasmic inclusion bodies. Immunohistochemical stains positive for vimentin, cytokeratin, desmin and muscle-specific actin, along with ultrastructural studies point to a myofibroblastic origin for the cells. Because of the benign nature of the lesions, observation is suggested.