An immunohistochemical study of abnormal keratinocyte proliferation in molluscum contagiosum

BACKGROUND: Molluscum contagiosum is a common cutaneous tumour that is characterized by usually spontaneous involution and self-limited spreading in immunocompetent individuals. OBJECTIVE: We aimed to investigate the apoptosis and the expression of cell-cycle proteins in molluscum contagiosum lesions. METHODS: The terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL)-based apoptotic index and the expression of the cell-cycle proteins Ki-67, p53, p21WAF and Bcl-2 were investigated in molluscum contagiosum lesions obtained from the trunk of 20 immunocompetent patients and in normal skin samples from the trunk of six healthy volunteers. RESULTS: Whereas molluscum contagiosum lesions displayed a TUNEL-based apoptotic index similar to that of normal skin, they exhibited an increased Ki-67 index, which was confined to the basal and first suprabasal layers (P < 0.001). Compared with normal non-sun-exposed skin, molluscum contagiosum lesions also exhibited increased p53 staining in basal cells (P < 0.01), increased p21WAF in suprabasal cells (P < 0.001) and loss of Bcl-2 expression. CONCLUSIONS: These results indicate that molluscum contagiosum lesions exhibit an increased proliferation rate of keratinocytes, which is likely to be partially counteracted by accumulation of p53.