Granular cell tumor of the extremity: Magnetic resonance imaging characteristics with pathologic correlation

Objective: The purpose of this study is to delineate the magnetic resonance (MR) appearance of a granular cell tumor (GrCT) of the extremity and to correlate the imaging appearance with the microscopic findings. Design and patients: A retrospective review of five patients with a histopathologic diagnosis of GrCT and pre-operative MR imaging of the neoplasm was done. The images were reviewed by two musculoskeletal radiologists in a consensus fashion. Lesion location, size, shape, margination, and signal intensity characteristics were assessed. MR findings were correlated with histopathological examination. Results: The benign subtype of GrCT is usually isointense or brighter than muscle on T1-weighted sequences, round or oval in shape, superficial in location, and 4 cm or less in size. On T2-weighted sequences, benign lesions may demonstrate a high peripheral signal, as well as a central signal intensity that is isointense to muscle or suppressed fat. A significant stromal component in the tumor and, hypothetically, a ribbon-like arrangement of tumor cells may influence the signal intensity demonstrated on the T1 and T2-weighted sequences. The malignant subtype may demonstrate signal intensity characteristics and invasion of adjacent structures often seen with other aggressive neoplasms; sizes larger than 4 cm and association with major nerve trunks can be seen. Conclusion: Benign GrCT has imaging characteristics which may distinguish this tumor from other soft tissue neoplasms, as well as the malignant type of this tumor.