Adenoid basal carcinoma of the cervix: a potential pitfall in cervicovaginal cytology

Adenoid basal carcinoma (ABC) of the cervix is a quite uncommon, indolent, yet invasive neoplasm rarely identified on cervicovaginal smears. This may be due in part to sampling. Unless ABCs become ulcerated, even vigorous brushing of the endocervical canal may not be adequate to dislodge the small, cohesive cells of this neoplasm. Fortunately, the association of ABC with squamous intraepithelial lesions (SIL) often results in its incidental diagnosis on follow-up cervical biopsy or endocervical curettage. We report two cases of ABC. In case 1, a 79-yr-old white woman was diagnosed with squamous-cell carcinoma on cervicovaginal (CV) smear. High-grade SIL, carcinoma in situ, and ABC were identified on subsequent cervical cone biopsy and hysterectomy. Retrospective evaluation of the CV smear revealed a few aggregates of small, uniform cells, with hyperchromatic nuclei representing fragments of ABC. In case 2, atypical basaloid cells suspicious for ABC were recognized on the CV smear of a 67-yr-old black woman, and ABC was subsequently confirmed on cervical cone biopsy. In neither case did the intervening cervical biopsy reveal ABC. In addition to a review of the clinical information useful in the diagnosis of ABC, the cytologic features of these two cases are compared with their subsequent histopathology and contrasted with other similar lesions comprising the differential diagnosis of small neoplastic cells found in cervicovaginal smears.