Case Report of a Distal Phalanx Interosseous Epidermoid Inclusion Cyst Presenting as an Enchondroma

Lesions in the distal phalanx can be attributed to a broad range of pathologies. Benign lesions such as enchondromas are common; however, there are a range of conditions that can mimic tumors on both clinical presentation and imaging.

Here, we report a case of a 42-year-old man who presented with pain and swelling in the distal phalanx of his right ring finger following trauma. Plain radiographs showed a fracture through a probable enchondroma in the distal phalanx, and this report was corroborated by an MRI. However intraoperatively, the lesion was found to be a caseous lesion encased in a capsule and histological examination revealed the lesion to be an intraosseous epidermoid inclusion cyst.

In this report, we discuss how enchondromas can be differentiated from intraosseous epidermoid inclusion cysts on clinical and imaging appearances. Intraosseous epidermoid inclusion cysts are more common in young males, with the previous trauma at the site of the lesion. Radiographically intraosseous epidermoid cysts can be differentiated by enchondromas by the absence of calcification within the lesion, and the location of the lesion in the subungal part of the distal phalanx. Ultimately, however, the definitive diagnosis of both lesions is histological and therefore it is important to maintain a broad differential when approaching the diagnosis of distal phalanx lesions.