Atypical immature metaplasia (AIM). A subset of human papilloma virus infection of the cervix.

Atypical immature squamous metaplasia (AIM) is a poorly understood lesion with uncertain biological and clinical significance. This report reviews 170 cases of cervical condylomata and 60 cases of high-grade cervical intraepithelial neoplasia (CIN II/III); AIM was found in association with 34% of condylomata and 16% of high-grade CIN. Thirty-seven cases of AIM alone were reviewed and nearly all presented with a cytologic diagnosis of CIN I or condyloma and a colposcopic appearance of white epithelium with or without punctation and mosaic structure. The mean ages of patients with condylomata, AIM, CIN II, and CIN III were 27, 27, 32, and 37 years, respectively. By immunoperoxidase techniques 75% of condylomata, 16% of AIM, and 0% of CIN lesions were positive. The histologic criteria for the diagnosis of AIM and it's morphologic distinction from CIN and relationship to condylomata, are outlined. AIM is a distinct histologic entity that shares similar epidemiologic, morphologic and biologic characteristics with condyloma. When AIM is found alone in biopsy material, careful correlation of cytology, and biopsy results should be performed and therapy should be based on the size and distribution of the lesion.