Histology of chronic pilonidal sinus.

Many theories concerning the development of chronic pilonidal sinus have been proposed. A histologic study of primary pilonidal sinus in 53 patients is presented. Subcutaneous tissue contained sinuses surrounded by chronic inflammation. Hair in sinuses was found in three quarters of the specimens examined. Examination showed that hair entered via one of the sinus openings created. Pits (defined as darker spots of varying width in the midline of the internatal cleft) were found to be indentations of the skin containing keratin plugs and debris. They may be isolated or connected with hair follicles. Pilonidal sinuses are chronic inflammatory processes of the skin caused by keratin plugs and debris clinically observed as pits, having penetrated the dermis.