Clinical and radiological characterization of fibrous hamartoma of infancy

Dear Editor,A newborn male patient presented with suspected obstetrictrauma due to increased forearm diameter. An X-ray of the fore-arm (Figure 1A) showed fracture of the ulna and bowing of theradius, together with increased thickness and density of the adja-cent soft tissues. Intravenous contrast-enhanced magnetic reso-nance imaging (Figures 1B, 1C, and 1D) revealed a heteroge-neous, infiltrative tissue formation, with ill-defined and thereforedifficult to measure borders, the epicenter of which was in theinterosseous membrane of the middle and distal thirds of the fore-arm. The formation was infiltrating the muscle planes on the volarand dorsal faces of the forearm and was in contact with the vascu-lar-nervous bundles, although there were no signs that it had in-vaded the bundles. The lesion created discontinuity in the middlethird of the ulna and the bowing of the radius. Heterogeneouscontrast enhancement was observed, as were lipid material fromthe lesion and fibrotic streaks.An incisional biopsy was performed. Histological and immu-nohistochemical analysis of the biopsy specimen demonstratedpositivity for vimentin alpha-actin and for S-100 protein, togetherwith negativity for desmin. On the basis of those findings, thedefinitive diagnosis of fibrous hamartoma of infancy (FHI) wasmade.A benign soft-tissue tumor that typically occurs in the firsttwo years of life