Disseminated superficial actinic porokeratosis. A histological review of 61 cases with particular reference to lymphocytic inflammation.

The pathology of 61 cases of disseminated superficial actinic porokeratosis was reviewed and the relative frequency of the histological features associated with the cornoid lamella and the pathology within and outside the porokeratotic rim were assessed. Papillary dermal lymphocytic infiltrate (97%), spinous layer vacuolar changes (90%), dyskeratotic cells in the epidermis (77%), and liquefaction degeneration of the basal layer (67%) were frequently seen under the cornoid lamella. Papillary lymphocytic infiltration was seen more frequently inside the porokeratotic ring in comparison to the outer skin. Lymphocyte marker studies in nine cases showed a predominance of activated T lymphocytes with positive LN3 and UCHL-1 staining. Together with the finding of a lichenoid reaction pattern, these results lend support to the hypothesis that actinic porokeratosis represents a migrating clone of abnormal keratinocytes with an associated immunological host response.