Presentation
Evaluate thenar mass.
Patient Data
There is a well-defined lytic lesion located centrally within the mid-diaphysis of the first metacarpal which has a thin sclerotic margin and central punctate calcfication. It is non-expansile and shows no evidence of cortical violation or overlying periosteal reaction.
There is also a large fat density mass within the thenar eminence, surrounding the first metacarpal and displacing the surrounding tissue. There are clear fat/tissue interfaces indicating little or no associated edema.
Lunotriquetral coalition is incidentally noted.
The lesion located within the first metacarpal demonstrates predominantly high fluid signal intensity with low T1 signal, and scattered areas of low/low signal intensity. It is well defined without surrounding edema, and does not violate the cotex.
There is also a large fat-signal intensity lesion anterior to the first metacarpal that extends between the opponens pollicus and flexor pollicis brevis. This lesion demonstrates no concerning septal thickening or enhancement, althoug pre-contrast T1 fat sat images would ideally be included for a confident diagnosis of benignity. The transverse low T1 high STIR signal band that spans the first metacarpal from the medial to the lateral apects of the lipomatous mass is somewhat disconserting, but does not enhance.
Lunotriquetral coalition is again noted.
Case Discussion
The 1st digit is the least common ray to find an enchondroma in the hand, and lipomas of the hand are likely equally rare. Having both in a similar location is simply bizzare and entertaining (to the radiologist), especially when throwing lunotriquetral coalition into the mix.
Case courtesy of Dr. Deborah Forrester
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