Differential diagnosis of T2 hypointense masses in musculoskeletal MRI

Many soft tissue masses have an indeterminate appearance on MRI, often displaying varying degrees and extent of T2 hyperintensity. However, a subset of neoplasms and tumor-like lesions may exhibit prominent areas of T2 hypointensity relative to skeletal muscle. The hypointensity observed on T2-weighted MRI can be caused by a variety of substances, including evolving blood products, calcifications or other inorganic crystals, or fibrous tissue. Carefully evaluating the presence and pattern of T2 hypointensity in soft tissue masses and considering potential causes in their associated clinical contexts can help to narrow the differential diagnosis among neoplastic and non-neoplastic possibilities. These include endometriosis, aneurysmal bone cysts, tenosynovial giant cell tumor, arteriovenous malformation and pseudoaneurysm, calcium pyrophosphate and hydroxyapatite deposition diseases, tumoral calcinosis, gout, amyloidosis, hemangiomas with phleboliths, low-grade fibromyxoid sarcoma, ossifying fibromyxoid tumor, collagenous fibroma, desmoid-type fibromatosis, myxofibrosarcoma, peripheral nerve sheath tumors, dedifferentiated liposarcoma, and treated sarcoma.

Automated summary

Soft tissue masses on MRI may show indeterminate appearances with varying degrees and extent of T2 hyperintensity, but some neoplasms and tumor-like lesions may exhibit areas of T2 hypointensity. Careful evaluation of T2 hypointensity and consideration of potential causes can help narrow down the differential diagnosis among various possibilities.