CD44 expression in normal human skin and skin tumors

CD44 is thought to be a principal cell surface receptor for hyaluronic acid. Although the distribution of hyalulonic acid has been studied, little is known about the distribution of the CD44 molecule in the human skin and skin tumors. This study was undertaken to investigate the distribution of the CD44 molecule in normal human skin as well as in benign and malignant skin tumors. In normal skin, CD44 was expressed on 1) keratinocyte cell surfaces throughout the epidermis except for the granular and horny layers, 2) hair follicular cells, 3) eccrine sweat gland cells, and 4) cell surfaces of dendritic cells in the dermis. In skin tumors, although CD44 was expressed on the tumor cell surface of seborreic keratosis, Bowen's disease, and squamous cell carcinoma as in normal skin, we could not detect any CD44 expression on the cell surface of the tumor cells of basal cell carcinoma. However, CD44 positive dendritic cells were observed in the tumor islands of basal cell carcinoma. Phenotypic analysis suggested that these CD44 positive cells were melanocytes.