Cervical cone biopsy has become an important surgical procedure for endocervical adenocarcinoma in situ (AIS), especially for patients who desire to retain their fertility. Establishing the usefulness of the endocervical margin status in cone biopsy specimens as a predictor of residual AIS is paramount. We examined the status of the endocervical margin in the cone biopsy specimen, the distance between the most proximal AIS and the endocervical margin in the cone biopsy specimen, and the endocervical curettage (ECC) specimen performed at the time of cone biopsy and residual AIS in the hysterectomy specimens of 61 patients with specimens accessioned from 1968 through 1997; 43 (30%) of patients with a negative endocervical margin had residual AIS in the hysterectomy specimen. Conversely, 10 of 18 (56%) patients with a positive endocervical margin in the cone biopsy Endocervical adenocarcinoma in situ (AIS) is an acknowledged precursor lesion of invasive endocervical adenocarcinoma.1-3 Hysterectomy has been the traditional surgical procedure for AIS. However, its routine use has been questioned because m a n y patients with AIS are in their childbearing years and desire to retain their fertility. [4][5][6][7][8] In this context, the cervical cone biopsy has become an important surgical procedure for AIS. The major concern of using the cone biopsy as a definitive surgical procedure is its ability to completely excise the AIS, because any AIS that is left in the uterus has the potential to progress to invasive a d e n o c a r c i n o m a . Predicting w h i c h patients have a high likelihood of having residual AIS in the uterus after cone biopsy is paramount. The specimen had no AIS in the hysterectomy specimen. All 6 patients with AIS in the ECC specimen had residual AIS. No patient with an endocervical margin in the cone biopsy specimen greater than 10 mm had residual AIS. Patients with distances less than 10 mm had equal percentages of residual AIS. In general, more patients with a negative endocervical margin in the cone biopsy specimen had no residual AIS in the hysterectomy specimen than those with a positive endocervical margin in the cone biopsy specimen. However, the status of this margin is not useful for p r e d i c t i n g the p r e s e n c e of r e s i d u a l AIS. Pathologists should report the distance between the endocervical cone biopsy margin and the closest AIS. (Key words: Cervix; Endocervix; Adenocarcinoma in situ; Cone biopsy; Margins) Am J Clin Pathol 1998,109:727-732. status of the margins in the cone biopsy specimen is a histologic feature that would seem to be predictive of residual AIS in the uterus, but some studies have suggested that this may not be the case. Furthermore, the optimum minimal distance between the endocervical margin in a cone biopsy specimen and AIS that would markedly reduce the likelihood of residual AIS has yet to be established. We retrospectively studied the specimens of patients with AIS who had undergone a cervical cone biopsy followed by hysterectomy to determin...