Evaluation and significance of hyperchromatic crowded groups (HCG) in liquid-based paps

Hyperchromatic crowded groups (HCG), a term first introduced into the cytology literature by DeMay in 1995, are commonly observed in Pap tests and may rarely be associated with serious but difficult to interpret lesions. In this study, we specifically defined HCG as dark crowded cell groups with more than 15 cells which can be identified at 10x screening magnification.

We evaluated consecutive liquid-based (Surepath) Pap tests from 601 women (age 17-74 years, mean age 29.4 yrs) and observed HCG in 477 cases. In all 477 HCG cases, Pap tests were found to be satisfactory and to contain an endocervical sample. HCG were easily detectable at 10x screening magnification (size up to 400 um, mean 239.5 um) and ranged from 1 to 50 (mean 19.5) per Pap slide.

HCG predominantly represented 3-Dimensional groups of endocervical cells with some nuclear overlap (379/477--79%), reactive endocervical cells with relatively prominent nucleoli and some nuclear crowding (29/477--6%), clusters of inflammatory cells (25/477--5.2%), parabasal cells (22/477--4.6%), endometrial cells (1/477--0.2%). Epithelial cell abnormalities (ECA) were present in only 21 of 477 cases (4.6%). 18 of 21 women with HCG-associated ECA were less than 40 years old; only 3 were = or > 40 years. HCG-associated final abnormal Pap test interpretations were as follows: ASCUS (6/21--28%), LSIL (12/21--57%), ASC-H (2/21--9.5%), and HSIL/CIN2-3 (3/21--14%). The association of HCG with ECA was statistically significant (p = 0.0174. chi-square test). In patients with ECA, biopsy results were available in 10 cases, and 4 cases of biopsy-proven CIN2/3 were detected. Among these four cases, HCG in the Pap tests, in retrospect represented the lesional high grade cells in three cases (one HSIL case and two ASC-H cases). Interestingly, none of the 124 cases without HCG were found to have an epithelial cell abnormality.

We conclude: a. HCG are observed in a high proportion of cervical smears. b. In the vast majority of cases, HCG are benign. c. ECA were only observed in cases with HCG. This observation is consistent with the hypothesis that the presence of HCG in Pap tests most often represents adequate sampling of the transformation zone, thus increasing the chances of detecting an epithelial cell abnormality. d. Only a few cases with HCG were associated with a serious ECA, but careful scrutiny of all HCG appears warranted to avoid the potential diagnostic pitfall of a significant false negative interpretation.