Expression of Epidermal Differentiation Markers in Seborrheic Keratosis

Lee, Jong Hee; Ahn, Hee Tae; Lee, Dong Youn; Cho, Kwang Hyun

Abstract

BACKGROUND: Seborrheic keratosis(SK) is a benign epidermal tumor histopathologically composed of basaloid cells and squamous cells.
OBJECTIVE
We investigated the mode of expression of various epidermal differentiation markers in SK.
METHODS
Twenty two cases of pathologically confirmed SK were collected from the pathologic files. The histological types included acanthotic type (19 cases) and reticulated type (3 cases). Immunohistochemical staining to various cytokeratins(CK), involucrin, loricrin and filaggrin was performed.
RESULTS
Two expression patterns of CK 1 were observed. There was diffuse homogeneous expression of CK 1 in squamous cells in 14 cases and in 8 cases heterogeneous expression with immunoreactive cells scattered among nonimmunoreactive cells to CK 1. Immunoreactivities to CK 14 were observed in basaloid cells. CK 6 was expressed in entire epidermis including basal layer in 19 cases. But stronger expression of CK 6 was expressed in squamous cells than in basaloid cells. In 3 cases immunoreactive cells to CK6 were squamous cells in spinous and granular layer. CAM 5.2 was focally expressed in basaloid cells only in one case. Expression of involucrin was observed in squamous cells in upper spinous and granular layer. Loricrin and filaggrin were expressed linearly in only uppermost granular layer or with horny layer.
CONCLUSION
CK expressions in SK suggest that differentiation process from basaloid cells to squamous cells is the same as that of from basal cells to sqamous cells in the suprabasal epidermis. Squamous cells of SK are activated keratinocytes which proceed normal keratinization with normal involucrin expression although terminal differentiation is presumptive to be slightly retarded because of decreased expression of loricrin and filaggrin.