Intraosseous epidermoid cyst - probable
History of remote trauma to finger about a year ago, currently complaing of pain.
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There is an expansile lucent lesion involving the tuft of the second phalanx with a cortical defect in the distal most aspect. There is scalloping of the volar aspect of the distal phalanx on the lateral view, suggesting possible remodeling from adjacent soft tissues. This lesion is likely benign in nature and may represent a giant cell tumor of the tendon sheath or an enchondroma. Other benign etiologies such as an epidermal inclusion cyst is also possible given the history of prior trauma to this region. A metastatic lytic lesion is a far less likely considered, given location. Incidental note of clubbing of the nailbeds.
The differentials of this case include: giant cell tumor of the tendon sheath (especially with the 2nd digit tuft volar bony remodeling), enchondroma (given its prevalence compared to the other differentials), or an epidermal inclusion cyst (consistent with the history). Metastasis is thought less likely given that the location would be rare.
A prior exam would have been very helpful (as always), but we did not have one.
Further evaluation with MRI can be helpful, especially with direct visualization of giant cell tumor of the tendon sheath. Patient did not return for follow-up...
The case brings up the interesting possibility that this may represent an intraosseous epidermoid cyst given the history.