Reclassification and analysis of clinical significance of atypical glandular cells on ThinPrep using The Bethesda 2001: Geneva experience

Background. The category "atypical glandular cells" (AGQ in The Bethesda System (TBS) 2001 represents equivocal glandular atypia. The objective was to determine the clinical significance of diagnosing AGC using new TBS 2001 on ThinPrep. There is scant information on the diagnosis of AGC and its outcome on ThinPrep using TBS 2001. Methods: 174 "ThinPrep((R))" Pap tests reported as atypical glandular cells of unknown significance (AGUS) using TBS 1991 during the period (2001-2004) were reclassified using AGC subcategories of TBS 2001. Follow-up histology was correlated with AGC subcategories of TBS 2001 and in women <40 and >= 40 years of age. Results: The mean AGC rate significantly decreased from 0.7% to 0.3%. (p <0.02). The frequency of clinically significant lesions on followup was higher with AGC diagnosis (51%, 21/41) than AGUS diagnosis (36%, 37/103). It was significantly higher for atypical endocervical cells favouring neoplasia (AEC-FN) (67%, 4/6) and AGC with concurrent squamous intraepithelial lesions (SIL) (67%, 8/12) than for the atypical endocervical cells, not otherwise specified (AEC-NOS) subcategory (12.5%, 2/16). All clinically significant lesions were high grade squamous intraepithelial lesions (HSIL) in women <40 years but in women >= 40 years, the majority (70%) were glandular. In categories atypical glandular cells favouring neoplasia (AGC-FN) and atypical endometrial cells (AEMC) all women had clinically significant glandular lesions. Conclusions: AEC-FN, AGC-FN, AEMC and AGC with concurrent SIL subcategories represented high risk diagnoses. The sequence of further investigations may vary by age and presence of postmenopausal bleeding.