Carton, Daly & Ramani: Clinical Pathology 
'Ask the Author' Forum
Figures from the bookCarton, Daly & Ramani: Clinical Pathology
October 2006: Transformation zone of the cervix
Q. I'm having trouble getting my head around the concept of the transformation zone of the cervix. Is it the same as the squamocolumnar junction?
A. This is a difficult area which is a common cause of confusion. Your question is best answered by looking at Figure 12.4 on p258 of Clinical Pathology. The transformation zone is the green area in parts C and D of the figure; it develops after puberty when the lower part of the endocervix becomes exposed to the acidic environment of the vagina and the surface glandular epithelium undergoes metaplasia into squamous epithelium. Microscopically, the transformation zone can be identified where squamous epithelium overlies endocervical glands. The transformation zone is so important because it is this area which can become dysplastic in some people with persistent infection by high risk types of human papillomavirus. The squamocolumnar junction is simply the point at which surface squamous epithelium meets columnar epithelium in the cervix. In parts A and B of the figure this is where the blue area meets the red area. After the development of the transformation zone, the squamocolumnar junction is where metaplastic squamous epithelium of the transformation zone meets the glandular epithelium of the endocervix i.e. where the green area meets the red area in parts C and D of the figure. I hope this helps!
View print version