34. Cervical intraepithelial neoplasia CIN III

Overview of the slide

Staining: PAS-H

Organ: Cervix

Description:

We can see two sections of a cervix. The top one is the best, so we’ll go with that. On the bottom left corner can we see a very PAS-positive area. Upon closer inspection can we see that the PAS positive cells are stratified squamous cells. The other epithelium found in this section isn’t PAS-positive. This epithelial layer is also much thicker than the other.

The PAS-negative epithelium contains pleomorphic cells (they have different shapes and sizes). These cells are larger than the PAS-positive cells as well. We can also see some cells undergoing mitosis here. A special cell type with a white “ring” around an irregular nucleus can be seen.

Diagnosis: Cervical intraepithelial neoplasia CIN III

This picture shows the abrupt change from healthy, PAS-positive epithelium to PAS-negative dysplasia.

Causes: HPV infection

Theory:

The normal epithelium here is the PAS-positive epithelium. The PAS positivity comes from the large amount of glycogen in the epithelial cells. Because the epithelium is stratified squamous and not columnar can we understand that this section is from the exocervix.

The PAS-negative epithelium has undergone dysplasia. These cells have lost their maturation and orientation, and some undergo mitosis. The loss of maturation and orientation has caused them to not produce glycogen like healthy cells do, which is why they’re PAS-negative. They are pleomorphic, meaning that the cells and their nuclei have varying shapes and sizes. They’re larger than normal epithelial cells, and don’t have the same shape as the healthy cells anymore.

Note also that the cells are pleiomorphic, i.e. they have different shapes and sizes and nuclei look different.

A special cell type called koilocytes can also be seen. These are the cells with the perinuclear halo and irregular nuclei. The presence of these cells is called koilocytosis or koilocytic atypia. Koilocytes are a sign of human papilloma virus (HPV) infection.

This dysplasia is part of a condition called cervical intraepithelial neoplasia, or CIN. This condition has three degrees of severity: CIN I – Dysplasia in only lower 1/3 of epithelium, CIN II – Dysplasia in lower 2/3 of epithelium, and CIN III – Dysplasia in the whole epithelium.

Any type of CIN is a precancerous lesion for cervical cancer. CIN III is the closest to becoming cancer while CIN I is the earliest stage. However, not all CIN III lesions become cancer – only 10% of them become cancerous. Because dysplasia is in the whole width of the epithelium in this slide it is classified as CIN III.