Immunohistochemical prognostic criteria in xeroderma pigmentosum.

Xeroderma pigmentosum (XP) is a rare inheritable disease characterized by severe sun sensitivity and early development of skin cancers. We compared the expression of cell proliferation markers and cell cycle checkpoint regulators in squamous cell carcinomas (SCC) and basal cell carcinomas (BCC) from patients with and without XP. Immunostaining for p53, Ki-67, and proliferating cell nuclear antigen (PCNA) was determined in SCCs and BCCs from 18 XP patients and 30 controls. Nine of the 18 XP patients had SCC and BCC, and the other nine had only SCC. In the control group, 15 moderately differentiated SCCs and 15 BCCs were evaluated. Expressions of p53, Ki-67 and PCNA in XP and non-XP patients were assessed statistically by using the Chi-square method. Expression of Ki-67 and PCNA was found to be greater in SCC from XP patients than controls (P = 0.021 and P = 0.033, respectively). Expression of PCNA and p53 by BCCs was greater in XP patients (P < 0.001 and P = 0.027, respectively). There was a significant difference in Ki-67 (P < 0.001) and PCNA (P = 0.001) expression between the lesions of the XP patients who died during the follow up and XP patients who survived. In XP patients, SCCs with more than 10% Ki-67 expression and %50 PCNA expression have a poor prognosis. Our results suggest that increased Ki-67 and PCNA expression may be a predictor for recurrence of nonmelanocytic skin cancer and a poor prognosis.