Expression of bcl-6 protein in normal skin and epidermal neoplasms.

Bcl-6 protein is a recently identified novel transcription factor whose deregulated expression is associated with diffuse large B cell lymphomas. It was recently shown by us that the protein is located in germinal center B cells and their neoplastic counterparts. In the present study, the expression of bcl-6 protein on normal epidermis, benign, and malignant tumors originating from epidermal cells, and squamous cell carcinoma (SCC) cell lines are investigated. With the use of immunohistochemistry, bcl-6 protein was shown to stain intensely on normal prickle cells, but none to only slightly on epidermal basal cells. Papillomas and keratoacanthomas copied their normal counterparts in the mode of expression. Various levels of expression were found on seborrheic keratoses, while the expression level on basal cell epitheliomas was low. Peculiarly, eccrine poromas and undifferentiated spindle-shaped basal cell epitheliomas were totally unstained. Squamous cell carcinomas showed a variety of expression levels, while two undifferentiated spindle-shaped carcinomas and one undifferentiated SCC cell line remained unstained. These results suggest that the expression of bcl-6 protein may be associated with morphological differentiation in normal and neoplastic epidermal cells.