BACKGROUND. The diagnosis of atypical squamous cells of undetermined significance (ASCUS) remains an enigma for the treating physician, because it encompasses both benign, reactive, as well as preneoplastic and possibly neoplastic conditions. To address this problem, The Bethesda System recommends qualifying the ASCUS diagnosis. This study analyzes the difference in the follow-up results between the various groups of patients with an ASCUS diagnosis as outlined by the Criteria Committee: favor premalignant (ASCUS-P), favor reactive (ASCUS-R), and unqualified (ASCUS-C). The outcome, based on follow-up biopsies and/or cytologies, for both the conventional Papanicolaou smear (CS) and liquid-based (LB) methodologies is compared. METHODS. The CS and LB biopsies and/or cytologies included 590 patients and 137 patients, respectively, who had an initial diagnosis of ASCUS. The final outcome after subsequent biopsy and cytology within a 1-year period for each methodology was tabulated. Furthermore, the addition of qualifiers for each diagnosis was tabulated for both cytology and biopsy follow-up and compared between CS and LB technologies. RESULTS. For CS, 29 patients (8.6%) were found to have squamous intraepithelial lesions (SIL) on subsequent cytologic smears, and 176 patients (63.7%) had SIL on biopsy follow-up. For LB, these numbers were 17 patients (19.1%) and 56 patients (65.1%), respectively. Regardless of the qualification used in the initial CS biopsy or cytology, over 90% of the subsequent smears resulted in a benign diagnosis. Biopsy outcomes after CS diagnoses of ASCUS-P, ASCUS-R, and ASCUS-C showed SIL in 80%, 53%, and 66% of patients, respectively. For LB diagnoses, subsequent smears detected SIL in 33% of patients with a diagnosis of ASCUS-P, 22% of patients with a diagnosis of ASCUS-R, and 12% of patients with a diagnosis of ASCUS-C. Biopsy outcomes after LB diagnoses of ASCUS-P, ASCUS-R, and ASCUS-C showed SIL in 68%, 64%, and 66% of patients, respectively. CONCLUSIONS, There appears to be no statistically valid benefit from a clinical point of view in qualifying an ASCUS interpretation by either CS or LB, except for CS evaluation of patients with a diagnosis of ASCUS-P. Cancer (Cancer Cytopathol) 2001;93:93-99. (C) 2001 American Cancer Society.
