Adenocarcinoma in situ of the cervix: an underdiagnosed lesion.

Although invasive adenocarcinoma of the cervix constitutes 5--15% of all cervical cancers, the in situ counterpart is underrepresented in the published series of percursor lesions of cervical cancer. Moreover, no cases are known to have been published in which in situ adenocarcinoma preceded invasive cancer. Partly, this can be explained by the fact that in situ adenocarcinoma is an underdiagnosed lesion. In a series of 52 cases of adenocarcinoma of the uterine cervix, 18 "negative" endocervical biopsies, taken 3--7 years prior to the clinical presentation of cancer, were available for study. In five of these cases, areas of adenocarcinoma in situ were found. The quantitative parameters of these "missed" adenocarcinomas in situ and adenocarcinomas in situ adjacent to invasive cancer were the same. The in situ lesions differed significantly from benign endocervical epithelium. This study strongly suggests that these lesions may progress to invasive cancer. With the acquired information on the quantitative features of adenocarcinoma in situ cells, the most significant criteria for routine diagnostic practice can be identified.