Immunohistochemical staining for the differentiation of subungual keratoacanthoma from subungual squamous cell carcinoma.

Summary Background.  Subungual keratotic tumours are rare. The clinical and histological distinctions between subungual keratoacanthomas (SUKAs) and subungual squamous cell carcinomas (SCCs) are important, but often difficult. Adequate methods of differentiation between the two are required, both for the purpose of management and for assessment of prognosis. Aim.  To establish the value of immunohistochemical staining patterns of proliferating cells to distinguish between SUKAs and subungual SCCs. Methods.  In total, 20 keratotic tumours from 20 patients were examined with immunohistochemical staining techniques using bcl-2, Ki67 and p53. Results.  Of 20 patients, 4 had SUKAs, 5 had cutaneous KAs, 6 had subungual SCCs and 5 had cutaneous SCCs. Our results showed that a high index of staining of p53 favours the diagnosis of subungual SCC over SUKA. Conclusion.  SUKAs do not express Ki67 strongly whereas some subungual SCCs do. Thus we conclude that immunohistochemistry for p53 and Ki67 may help distinguish between a subungual SCC and a SUKA.