Many in situ neoplasms are regarded as being located within a continuum of morphological change between dysplasia and invasive cancer. For example, for cervical intraepithelial neoplasia (CIN) three grades are recognized, the third of which (CIN III) includes both severe dysplasia and carcinoma in situ. This system of grading has been extended to other organs, such as vulva and vagina. Descriptions of grade III intraepithelial neoplasia, with or without mention of severe dysplasia, are assigned to this section; grades I and II are classified as dysplasia of the organ system involved and should be coded to the relevant body system chapter.