Immunohistochemical Study of Localization of Involucrin in Normal and in Lesioned Skin

Abstract

Involucrin is a soluble protein precursor of the cross-linked envelope of epidermal keratinocytes and a most useful marker for the early stage of terminal differentiation. We examined the localization of involucrin, using an immunoperoxidase technique. The normal epidermis showed that involucrin was localized in the stratum granulosum and upper stratum spinosum. In the appendages, the infundibulum, the layers of the inner root sheath in the hair follicles and sebaceous ducts showed immunoreactivity for involucrin. As to the lesioned skin, proliferating lesions formed by basal oid cells (seborrheic keratosis, actinic keratosis and basal cell epithelioma) were negative for involucrin, while that formed by squamoid cells (psoriasis vulgaris, lichen planus, keratoacanthoma, Bowen’s disease and squamous cell carcinoma) show immunoreactivity for involucrin. In the squamoid lesions, patterns of staining for involucrin differed between benign lesions and malignant neoplasmas: the former showed a uniform staining but the latter showed an irregular staining of various intensities involving a patchy or patchwork-quilt pattern. Thus, involucrin aids in making a differential diagnosis of these lesions. Lichen planus and the overlying epidermis of actinic keratosis showed granular staining for involucrin, a finding suggestive of damage of the basal layer.