The immunohistochemical expression of keratins 7, 8, 10, 13, 14, 17, 18 and 19 was examined in formalin-fixed paraffin-embedded tissues of normal uterine cervical epithelium and carcinomas of cervical origin (4 squamous cell carcinoma in situ, 17 squamous cell carcinoma, 9 adenocarcinoma, and 1 adenoid basal carcinoma). A panel of 8 monoclonal antibodies capable of recognizing 8 individual keratin subtypes was employed using microwave oven heating and a labeled streptavidin biotin method. Ectocervical squamous epithelium expressed keratins 14 and 19 in the basal cell layer, and keratins 10 and 13 in the suprabasal cell layer. Endocervical columnar cells were found to express keratins 7, 8, 18 and 19, whereas the reserve cells expressed keratins 7, 8, 14, 17, 18 and 19. Most of the squamous cell carcinomas, both keratinizing and non-keratinizing, as well as the carcinoma in situ revealed a keratin phenotype detected in normal ectocervical squamous cells (keratins 10, 13, 14 and 19) and endocervical subcolumnar reserve cells (keratins 7, 17 and 18). The adenocarcinomas, both endocervical and endometrial type, were positive for keratins 7, 8, 17, 18 and 19. The adenoid basal carcinoma expressed all the keratins examined including the expression of reserve cell keratin. Reserve cell keratins were found mostly in squamous cell carcinomas, adenocarcinomas and adenoid basal carcinoma of cervical origin. Therefore, the keratin expression pattern indicates the origin of a variety of carcinomas of the uterine cervix from a common progenitor, endocervical reserve cells.

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