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'''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 we know this section is from the exocervix. | '''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 we know 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 makes them PAS-negative. They are pleomorphic. They’re larger than normal epithelial cells, and don’t have the same shape as the healthy cells anymore.[[File:CIN III pleiomorphism.png|thumb|Note also that the cells are pleiomorphic.]]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 HPV infection. | 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 makes them PAS-negative. They are pleomorphic. They’re larger than normal epithelial cells, and don’t have the same shape as the healthy cells anymore.[[File:CIN III pleiomorphism.png|thumb|Note also that the cells are pleiomorphic.]]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 HPV infection. |