Patterns of keratin 19 expression in normal, metaplastic, condylomatous, atrophic, dysplastic, and malignant cervical squamous epithelium.

Keratin 19 (K-19) expression has been strongly correlated with dysplasia in oral epithelium. Expression of K-19 was evaluated by immunoperoxidase staining in formalin-fixed normal ectocervical tissue, normal endocervical tissue, cervical dysplasia, squamous metaplasia, atrophic epithelium, cervical condylomas, and invasive carcinoma to determine if a correlation of K-19 expression with dysplasia was present in the cervical epithelium. Uniform expression of K-19 was seen in endocervical epithelium and in the basal layer of normal ectocervical epithelium in all areas where these epithelia were present. Cervical dysplasia without associated condylomatous changes showed increased expression of K-19 in suprabasal epithelium, corresponding to the level of immature cells. Squamous metaplasia was characterized by scattered cells with increased staining (patch-quilt pattern). There was considerable overlap in the patterns of K-19 expression in dysplastic and metaplastic epithelium. Thus K-19 staining pattern could not be used as a distinctive marker for dysplasia in the cervical epithelium. Atrophic epithelium showed a characteristic uniform but low-level expression of K-19 in suprabasal areas. This pattern may be of diagnostic use in differentiating atrophic lesions from dysplasia. Condylomas showed focal loss of K-19 in the basal layer, suggesting induction of premature differentiation in the basal layer by human papillomavirus infection. Invasive carcinomas showed variable patterns. K-19 is a marker of immature cervical squamous epithelium, with generally distinctive but sometimes overlapping patterns of expression in various diagnostic categories.