Subungual Exostosis
Subungual exostosis is an uncommon bony tumor of the distal phalanx most often seen on the hallux. Although this lesion is completely benign, it must be distinguished from a number of other subungual tumors, both benign and malignant. Radiography of the digit is a noninvasive test that should be part of the initial workup whenever subungual exostosis is in the differential diagnosis. Once identified, surgical removal of the exostosis generally is both effective and well tolerated. We present a case of subungual exostosis that was discovered incidentally during a full-body skin examination. We also review the pertinent clinical and histopathologic findings, diagnosis, and treatment of this entity.
Practice Points
- Subungual exostosis is a benign tumor that is most common on the hallux.
- Plain radiographs can identify an exostosis and should be part of the initial workup of any subungual tumor.
- Surgical excision is an effective and well-tolerated treatment of subungual exostosis.
The most commonly accepted treatment of subungual exostosis is a localized excision. Partial or total removal of the nail has traditionally be advocated to ensure complete excision of the exostosis, a nail-sparing technique that has been shown to enhance cosmetic results.3 Incomplete excision and incomplete maturation of the lesion have been reported to be responsible for almost 50% of recurrences.3 This high recurrence rate is due to difficulty in ensuring a total excision because the gradual merging of the fibrocartilage cap with the overlying nail bed makes it impossible to develop a cleavage plane5; as a result, it has been suggested that excision should only be attempted after maturation of the tumor so the cleavage plane can fully develop. Other studies claim that delaying treatment can result in elevation and deformity of the nail, pain, and secondary periungual infection.3
Conclusion
Subungual exostosis is a benign bony tumor of the distal phalanx that can cause pain and onycholysis. Radiography of the affected digit is a noninvasive way to confirm the diagnosis and should be part of the initial workup of any suspicious subungual tumor. Once identified, complete removal of the exostosis by excision has been shown to be an effective treatment with few complications.
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