High incidence of demodicidosis in eyelid basal cell carcinomas

Although UV radiation is the major cause of basal cell carcinoma (BCC), local factors, such as chronic trauma, irritation, or inflammation, may also have some role in its etiopathogenesis. The pilosebaceous follicle mites, Demodex folliculorum and D. brevis, inhabit most commonly and densely certain facial skin areas, including the nose and periorbital regions, where BCC also develops most frequently.

To investigate, in a retrospective histopathologic study, whether a possible etiopathogenetic relationship exists between demodicidosis and eyelid BCCs.

We examined 32 eyelid BCC specimens that contained at least five eyelashes or five hair follicles with respect to the presence and density of Demodex mites. As controls, we evaluated 34 matched specimens consisting of benign eyelid skin lesions.

Twenty-one of 32 BCC cases (65.6%) and eight of 34 control cases (23.33%) had demodicidosis. Mean mite counts were 1.31 +/- 1.57 and 0.47 +/- 0.99 in BCC cases and controls, respectively. The differences were significant for both prevalence (P < 0.001) and density (P = 0.0052). Although there was a significant positive correlation between increasing mite number and patient age in the control group (r = 0.47, P < 0.05), no significant correlation was found between these two factors in BCC cases (r = -0.102, P > 0.05).

Demodicidosis may be one of the triggering factors of carcinogenesis in eyelid BCCs in otherwise predisposed people due to its traumatic/irritating effect or chronic inflammation.