The inherent longetivity of stem cells causes them to be susceptible to multiple genetic hits. Thus, it is not surprising that stem cells are implicated in the etiopathogenesis of select cutaneous
neoplasms. However, most studies to date are restricted to the use of a single marker (p63,
cytokeratin-15 or
cytokeratin-19) and do not appear to compare distribution of stem cell markers in a spectrum of cutaneous in situ versus invasive epithelial
malignancies. In this study, we evaluate expression of
cytokeratin-15,
cytokeratin-19, and p63 in a series of primary cutaneous epithelial lesions that include
actinic keratosis (n=29),
squamous cell carcinoma in situ (
n=30), bowenoid papulosis (n=15) and
squamous cell carcinoma, well differentiated (n=29) in order to evaluate the role of stem cell marker expression in the grading and development of in situ and invasive
malignancies. For
cytokeratin-15, expression was retained in
actinic keratosis (38%),
squamous cell carcinoma in situ (53%) and bowenoid papulosis (60%) but appeared to be lost in
squamous cell carcinoma (3%) with statistically significant differences observed between groups that retained versus those that did not (P<0.05 for all three); for
cytokeratin-19, patchy yet basal expression was noted in
actinic keratosis (21%), patchy and suprabasal expression was noted in
squamous cell carcinoma in situ (37%), bowenoid papulosis (13%) and
squamous cell carcinoma (24%) with no statistically significant differences between groups; for p63, expression was retained in
actinic keratosis (90%),
squamous cell carcinoma in situ (87%), bowenoid papulosis (60%) and
squamous cell carcinoma (100%) with no statistically significant differences between groups. In summary, our findings expand the
neoplasms which involve stem cells to include cutaneous epithelial
malignancies. Differential localization of each of these markers argues in favor of stem cell heterogeneity.