CD34-positive dendritic cells disappear from scars but are increased in pericicatricial tissue

CD34-positive stromal cells (CD34SC) are distributed throughout the body, including the dermis. They are thought to play a role in maturation and proliferation of adjacent mesenchymal and epithelial stem cells and in immune responses. To investigate the role of such cells in wound healing after excision of cutaneous lesions, we examined the distribution and quantity of CD34SC in scars from the sites of removal of malignant skin tumors and from reconstructive surgery, as well as in samples of normal skin. In normal skin, CD34 staining was confined to dendritic cells in the dermis, endothelial cells, perifollicular cells and eccrine glands. In cutaneous scars, the cicatricial tissue was totally devoid of CD34SC. However, the dermis adjacent to scar showed increased numbers of CD34SC as compared with normal skin [41.5 cells/mm(2) vs. 24.5 cells/mm(2) (p < 0.001)]. We conclude that CD34SC disappears from scars but are induced to proliferate in pericicatricial tissue. The cells in question may play a role in remodeling of scarred skin. One should be aware that augmented labeling for CD34SC around scars is common; it should not be interpreted as evidence for the persistence or recurrence of tumors that may also express CD34.