The treatment failure with the terbinafine made onychomycosis unlikely, and the appearance of the finger did not suggest that this was a wart. So, the physician opted for a 4-mm punch biopsy of the lateral nail fold, which confirmed that this was a well-differentiated squamous cell carcinoma (SCC) of the fingertip.
Periungual SCC is twice as common in men as women. Lesions tend to appear as hyperkeratotic plaques or nodules, pushing the nail plate away from the nail bed. With onychomycosis, one would expect the nail to be more thickened and discolored. A wart would not be as keratotic as this lesion was, and there would be thrombosed capillaries on closer inspection.
SCC is the second most common skin cancer in humans. It is most common on sun-exposed areas but may present in sites not exposed to the sun. It has been hypothesized that high risk human papillomavirus (HPV) types—particularly HPV 16—may contribute to diseases of the fingertips and nail unit in older adults. (There was no known history of HPV in this patient.)
A surgical approach often is curative. Achieving appropriate margins occasionally requires partial amputation. Mohs micrographic surgery (MMS) offers the highest cure rate and spares as much uninvolved tissue as possible. Radiation therapy is another tissue-sparing technique. It requires 15 to 30 sessions over 3 to 6 weeks and has a lower cure rate than MMS.
In this case, the patient underwent MMS. Follow-up skin surveillance exams revealed other small nonmelanoma skin cancers at other sites. The patient also developed a dystrophic nail spicule near the surgical site that was re-excised and deemed benign.
Photos and text for Photo Rounds Friday courtesy of Jonathan Karnes, MD (copyright retained). Dr. Karnes is the medical director of MDFMR Dermatology Services, Augusta, ME.