RESUMO
BACKGROUND: The epidermis and adnexal epithelium might express different types of keratin (K) during fetal development. OBJECTIVE: The objective is to observe the distribution of K8/18 in the skin of fetuses and to find out the distinction of expressions of K8/18 during fetal development. METHODS: Immunohistochemical analysis was applied to the skin of the scalp and sole of 42 fetuses ranging from 10 to 39 weeks of gestation. Immunohistochemical staining with monoclonal antibodies with CAM5.2 using LSAB kit against K8/18 was conducted. RESULTS: In the skin of the scalp, K8/18 was expressed in the periderm and basal layer of epidermis from the 10th week to the 31st week of fetal gestation. K8/18 was expressed in the hair germ, bulge and basal cells of fetal the infundibulum and sebaceous glands. Root sheath cells were weakly positive but matrix cells were negative. The expression of K8/18 was negative in the basal layer of the sole. Merkel cells, which are located in the basal layer and upper dermis, were positive from the 12th week of gestation. Terminal eccrine ducts and acinar cells were positive after the 20th week of gestation. CONCLUSION: K8/18 in the skin of the scalp and sole of fetuses were expressed in different ways. The expression of K8/18 in the basal cells of the sole were negative while basal cells of the epidermis of the scalp were positive transiently from the 12th to the 31st week of gestation. Early hair germ cells and bulge cells were expressed strongly in hair follicles. Terminal eccrine ducts and acini were expressed strongly in the eccrine gland. Merkel cells located in the basal layer and papillary dermis also express K8/18.