Ultrastructural appearances of disseminated superficial actinic porokeratosis

Morphogenesis of the cornoid lamella: histochemical, immunohistochemical, and ultrastructural study of porokeratosis

To elucidate the morphogenesis of cornoid lamellae (CL) in porokeratosis, skin lesions of three cases of disseminated superficial actinic porokeratosis and a case of linear porokeratosis were examined. By N-(7-dimethylamino-4-methyl-3-coumarinyl)maleimide staining, SH groups were present in the living layer of the epidermis beneath CL and irregularly disappeared at the bottom of CL, whereas SS linkages appeared in dyskeratotic cells in the living layer and in the irregularly shaped cell membranes of the horny cells. Epidermis beneath CL showed an increased and irregular involucrin expression. Ultrastructurally, the living keratinocytes contained many cytoplasmic vacuoles and had a smaller number of lamellar bodies than normal. Intercellular lamellar sheets were incompletely formed. The dyskeratotic cells and the lower horny cells contained many small vacuoles but formed a marginal band. The horny cells of CL also formed a marginal band and, further, a keratin pattern. CL may be formed by hyperproliferative atypical kertatinocytes which keratinize rapidly and irregularly and show defective desquamation due to the paucity of intercellular lamellar sheets.

Scanning electron microscopy of disseminated superficial actinic porokeratosis

A typical skin lesion from a patient with biopsy-confirmed disseminated superficial actinic porokeratosis (DSAP) was examined by scanning electron microscopy. The lesion was rimmed by a prominent but discontinuous cornoid lamella. The cornoid lamella was found to consist of a packed layer of keratinocytes whose orientation varied from parallel to the epidermis at the base of the lesion to perpendicular at the summit of the porokeratotic column. The central core of the cornoid lamella consisted of a tightly packed mass of keratin.

Squamous cell carcinoma in porokeratosis in two patients

Malignancy arising in porokeratoses is a well recognised but infrequently reported complication. Histological studies suggest that malignancy arises from the abnormal clone of keratinocytes which produce the cornoid lamella. We report two cases of squamous cell carcinoma arising in porokeratoses and postulate genetic, environmental and host factors as important in the evolution of their malignancy.

Disseminated superficial actinic porokeratosis: a clinical study

Disseminated superficial actinic porokeratosis is an autosomal dominant condition that requires sun exposure for full expression. It affects only sun-exposed areas, with relative sparing of the face. In sun-damaged skin of Australians disseminated superficial actinic porokeratosis is commonly mistaken for solar keratosis. Twenty-nine subjects with disseminated superficial actinic porokeratosis were involved in an extensive questionnaire and clinical study. The distribution of lesions was charted on all subjects, with a mean count of 268 lesions per subject. We found no evidence that skin cancer had arisen in disseminated superficial actinic porokeratosis lesions. A review of the etiologic and clinical features of disseminated superficial actinic porokeratosis also is presented.