Lingering wart raises suspicion
The skin over the posterior nail fold had thickened and spread up towards the DIP joint line. The nail had been elevated from the nail bed at one edge. There was certainly warty-like thickened skin at the other edge. However a biopsy of the skin behind the posterior nail fold was reported as squamous cell carcinoma in situ. This was surprising. Papilloma virus can be oncogenic but these serotypes are usually seen in the genital or oral areas.
The next step was to remove the nail to obtain access to the lateral nail beds and to punch biopsy both lateral edges of the nail bed