The endocervical canal is lined by columnar epithelium on a basement membrane. There are also endocervical glands, and its extension is influenced by age, parity and hormonal status. The Squamous Columnar Union (SCJ) is in constant change throughout the life of the woman, there is a constant transformation from columnar to squamous epithelium, which is known as squamous metaplasia. Lesions of the cervix can be produced by trauma (tears, holes or ulcerations), infection: such as those caused by sexually transmitted agents (Chlamydia trachomatis, Neisseria gonorrhea, Trichomonas, herpes virus, or HPV), and neoplasms, that can be benign represented by endocervical polyps or fibroids, endometriosis, or malignant.
For analysis of premalignant cervical lesions, we use the 2001 Bethesda System, which organizes cervical cells from normal to carcinoma in situ, both originated from squamous cells, and from the glandular epithelium. In 1975, for the first time, the possible association between HPV and cervical cancer was noted, and 8 years later Zur Hausen and then Walmoeers and Bosch demonstrated the possibility to isolate the virus from cervical biopsies.
http://www.hysteroscopy.info