The association of atypical squamous cells, cannot exclude a high grade squamous intraepithelial lesion, hyperchromatic crowded groups and high grade squamous intraepithelial lesions involving endocervical glands.

Background: Hyperchromatic crowded groups (HCGs) are often classified as atypical squamous cells, cannot exclude a high grade squamous intraepithelial lesion (ASC-H) on ThinPrep Pap tests. This study reports on the association of HCG's with high grade squamous intraepithelial lesions (HSIL) involving endocervical glands.

Methods: Over a 3-year period (January 1, 2018-December 31, 2020), 115 (0.2%) of 63,817 Pap tests were diagnosed as ASC-H. Histologic follow-up was available in 76 (66%) cases; 42 (55%) cervical biopsies; and 34 (45%) cervical cones/LEEPs.

Results: Based on the histologic results, 49 ASC-H cases showed HSIL/CIN 3 and form the basis of this study. ThinPrep Pap tests showed two cell patterns; atypical immature squamous metaplastic cells and HCGs, each of which was difficult to distinguish from HSIL. On histologic correlation all 10 ASC-H Pap Tests with individual atypical immature squamous metaplastic cells showed HSIL/CIN 3 without endocervical gland involvement and 37 (95%) of the 39 Pap Tests with HCGs showed HSIL/CIN 3 with endocervical gland involvement.

Conclusion: The results of this study support the premise that a subset of HCGs represent endocervical gland involvement by HSIL as opposed to a glandular lesion; in particular endocervical adenocarcinoma in-situ.