Subcutaneous granuloma annulare: MR imaging features in six children and literature review

PURPOSE: To describe the magnetic resonance (MR) imaging findings of subcut aneous granuloma annulare (StA), a rare mass of early childhood. MATERIALS AND METHODS: MR imaging studies and clinical records in six child ren aged 2 1/2-4 years in whom SCA was diagnosed between 1993 and 1997 were retrospectively reviewed. All MR imaging examinations included T1-weighted and fast spin-echo T2-weighted sequences. Three children received intraven ous contrast material. The diagnosis was established by using excisional bi opsy results, with confirmation by means of characteristic features in muci n-stained specimens. RESULTS: All children presented with a nontender, nonmobile mass. The lesio n in all six children was confined to the pretibial (n = 5) or prepatellar (n = 1) soft tissues. MR imaging characteristics were uniform. Masses were subcutaneous in location and had ill-defined margins. On T1-weighted images , the lesion was isointense or slightly hyperintense to muscle. On T2-weigh ted images, the signal intensity was more heterogeneous, but the lesion was predominantly hyperintense. In three children who received contrast materi al, the lesion enhanced nearly homogeneously. CONCLUSION: Although SCA can often be diagnosed on the basis of clinical ch aracteristics, MR imaging may be requested by practitioners unfamiliar with the lesion. In these cases, with recognition of typical MR imaging feature s, a limited biopsy and specific histologic preparation that includes mucin staining can be recommended.