- lobulated oval soft tissue mass surrounding the diaphysis of the fifth metacarpal at the palmar surface (hypothenar eminence).
- The mass shows high signal on fluid sensitive sequences with few millimetric cystic changes and multiple hypointense linear septa. It also shows avid heterogenous enhancement postcontrast administration.
- The mass causes scalloping with cortical loss of the palmar fifth metacarpal cortex at the mid diaphysis with marked bone marrow edema of the fifth metacarpal and adjacent soft tissue.
- The mass surrounds approximately 50% of the diameter of the proximal flexor digiti minimi tendon and completely encases the proximal extensor digiting minimi causing mild narrowing of the tendon.