ENDOMETRIAL CELLS OF THE LOWER UTERINE SEGMENT (LUS) IN CERVICAL SMEARS OBTAINED BY ENDOCERVICAL BRUSHINGS - A SOURCE OF POTENTIAL DIAGNOSTIC PITFALL

The use of endocervical brushes has led to a generous sampling of both endocervical and ''lower uterine segment'' (LUS) cells. To an unfamil iar eye, the large fragments of endometrial tissue from the LUS may le ad to misinterpretation as endometriosis or glandular malignancy, as h appened in our institution when the use of endocervical brush and reco gnition of LUS cells in cervical smears were limited. Eight cases, cyt ologically interpreted as such, were proven to be benign following cer vical biopsy or endometrial curettage. The nature of LUS cells was rec ognized only on retrospective review of this cytologic material. Howev er, in recent years, routine use of the endocervical brush resulted in an influx of similar cases referred by the cytotechnologists to the p athologist as glandular atypia. Thus, to get familiarized with the cyt omorphology of LUS cells and its diagnostic pitfalls, a prospective st udy was undertaken. This entailed a review of 62,187 consecutive cervi covaginal smears (women of post-hysterectomy status were excluded) rec eived within a 12-mo period (July 1, 1992-June 30, 1993). A total of 3 44 smears (0.55%) showed large tissue fragments of branching tubular e ndometrial glands with and without surrounding stroma. Patients ranged from 14-82 yr of age. History of cervical cone biopsy was noted in ni ne patients (2.6%). Repeat cervical smear or concurrent endometrial or endocervical biopsy available in 84 patients (24.4%) were negative. L US cells may be mistaken for endometriosis, epithelial glandular atypi a, as well as carcinoma of both endocervical and endometrial origin. I n addition to glandular abnormality, LUS cells may also be misinterpre ted as that of squamous intraepithelial lesion. The characteristic pre sentation of LUS cells with long tubular branching glands embedded in a loose monomorphic stromal cells containing delicate capillaries is b est appreciated at low power magnification. Familiarity with the cytom orphologic features of LUS and awareness of the diagnostic pitfalls ma y avoid interpretative errors and unnecessary surgical procedures. (C) 1995 Wiley-Liss, Inc.