In-situ and microinvasive adenocarcinoma of the uterine cervix. A clinical, cytologic and histologic study of 14 cases. Am J Clin Pathol 64: 155-70, 1975. The clinicopathologic features of 14 cases of in-situ and microinvasive adenocarcinoma of the cervix, encountered during the period 1961-1974, form the basis of this report. Seven cases represent examples of in-situ and seven, microinvasive adenocarcinoma. Severe dysplasia and carcinoma in-situ of the squamous epithelium were coincidental finds in 12 patiients. Papanicolaou smears were abnormal in all 14 patients. In nine, malignant glandular cells were identified. Five smears contained both malignant squamous and glandular cells. The mean age of the 14 patients was 38.4 years. Thirteen patients had borne one to six children. Two were pregnant at the time of diagnosis, and four were on birth control medication. Thirteen of the patients underwent conization biopsy. Hysterectomy in one form or another was curative in all. The relatively infrequent occurrence of in-situ adenocarcinoma is probably due to the low incidence of cervical adenocarcinoma and to the fact that the lesion is focal and easily overlooked. Five of the cases in the present series were a chance finding in a review of 200 consecutive cone biopsies of the cervix. The resemblance of the in-situ lesions to carcinoma and the presence of morphologically similar glandular tissue adjacent to foci of microinvasion suggests that the in-situ lesion is the precursor of invasive adenocarcinoma of the cerivs.