Atypical squamous cells of undetermined significance: correlative histologic and follow-up studies from an academic medical center.

The diagnosis of ASCUS (atypical squamous cells of undetermined significance) was introduced in the 1988 Bethesda System for reporting cervical/vaginal cytologic findings. Outcome and appropriate management of patients with this diagnosis is not presently established. Criteria defining ASCUS are nuclear enlargement (2.5-3.0 times normal intermediate cell nucleus), mild nuclear hyperchromasia, smooth nuclear outlines with mild variation in nuclear size and shape, or else two, but not all three, cytologic criteria for human papilloma virus (HPV) cytopathic effect. All 668 cases reported as ASCUS from February 1992-December 1993 from our cytology laboratory were reviewed. These ASCUS cases represented 4.5% of all gynecologic cases diagnosed in that same time period. Of these, 284 (41%) had a subsequent colposcopic biopsy and/or endocervical curettage. The biopsied cases included 101 (36%) with condylomata, 38 (13%) with cervical intraepithelial neoplasia (CIN) I, 17 (6%) with CIN II, and 9 (3%) with CIN III. No cases of carcinoma were detected. Of patients with a cytologic diagnosis of ASCUS and subsequent cervical biopsy, 49% had low-grade cervical intraepithelial neoplasia (LGSIL), either condyloma or CIN I. Nine percent had high-grade cervical intraepithelial neoplasia, either CIN II or CIN III. These findings indicate that ASCUS defines cytologically a group of patients who may have either a concurrent or subsequent development of a squamous intraepithelial lesion (SIL). This forms a high-risk group. The management of cases with a cytologic diagnosis of ASCUS should be at least as aggressive as that of LGSIL.