Muscular sarcoidosis: findings at MR imaging

Twelve patients with muscular sarcoidosis were evaluated with magnetic resonance (MR) imaging: Nine patients had the nodular type and three had the myopathic type of muscular sarcoidosis. The nodular type showed a characteristic appearance on MR images. In each patient with the nodular type, both T1- and T2-weighted axial spin-echo images showed an oval nodule consisting of a star-shaped area of low signal intensity surrounded by an area of high signal intensity. Histopathologic correlation in patients with the nodular type revealed that the central portion of the nodule was fibrotic tissue surrounded by inflammatory granulomatous tissue. In each patient with the myopathic type of muscular sarcoidosis, MR images failed to show any abnormality; the authors hypothesize that this failure correlated with the sparse distribution of epithelioid cell granulomas. Identification of the star-shaped area of low signal intensity may help in the diagnosis of muscular sarcoidosis and the differentiation of lesions associated with sarcoidosis from other soft-tissue masses.