Ectopic decidual reaction of the uterine cervix: frequency and cytologic presentation.

The histologic and cytologic manifestation of cervical decidual reaction in pregnancy was investigated. Histologically, cervical decidua was found in 30.8% of 191 uteri removed during pregnancy. Characteristic features were focal occurrence, subepithelial location and frequent disruption of the overlying epithelium. Cytologically, decidual cells were found in 34% of patients with histologically confirmed cervical decidual reaction. The number of decidual cells per smear ranged from 11 to 208, with a mean of 105. The majority of cells occurred in aggregates and stained basophilic or amphophilic. Outstanding diagnostic features of decidual cells in smears were finely granular chromatin pattern in 96%, prominent nucleoli in over 80% and marked nuclear enlargement. Cytometrically, decidual cells showed a wide variation in size. The nuclear area ranged from 31 sq micrometers to 320 sq micrometers, with a mean of 111 sq micrometers. In the differential diagnosis, tissue repair, dysplasia, carcinoma in situ and endocervical adenocarcinoma must be considered.