Magnetic Resonance Imaging of T2-weighted Hypointense Nodular Lesions of the Foot and Ankle: A Pictorial Review of Rheumatoid Nodules, Tophaceous Gout, and Tenosynovial Giant Cell Tumor

Abstract: Nodular soft tissue abnormalities are common in the foot and ankle and often demonstrate overlapping magnetic resonance imaging features, typically showing high signal intensity on T2-weighted sequences. In contrast, T2-weighted hypointense soft tissue nodules are less common and encompass a range of neoplastic and pseudotumoral entities. Among these, Morton's neuroma is likely the most prevalent abnormality; however, other less common but clinically relevant lesions may appear with similar imaging features. Abstract: This article focuses on three such conditions: rheumatoid nodules, tophaceous gout, and tenosynovial giant cell tumor. Although the imaging findings of these lesions themselves are often nonspecific, the associated features can provide important diagnostic clues. Rheumatoid nodules typically occur around the metatarsophalangeal joints, in areas subject to repeated mechanical stress, and usually present as multiple lesions with accompanying intermetatarsal bursitis. In contrast, tophaceous gout is rarely associated with interdigital bursitis, but more commonly it shows diffuse fatty muscle infiltration. Tenosynovial giant cell tumors are typically limited to a single joint space or tendon sheath and usually not associated with bursitis, pseudobursae, or fatty infiltration of the muscles.