BACKGROUND. Developed in 1989, the Bethesda System has largely replaced pre
vious classifications of Papanicolaou (Pap) smears front the uterine cervix
. The system is binary, dividing smears into two groups - low-grade, squamo
us, epithelial lesions (LSIL) or high-grade, squamous, epithelial lesions (
HSIL). A third category, atypical squamous cells of undetermined significan
ce (ASCUS), is used to classify minimal cellular changes that do not satisf
y the criteria for the low- or high-grade categories. This study was design
ed to confirm the utility of this binary division and to compare the result
s with another classification system (the Munich II Nomenclature) that is n
ot binary but contains three divisions or grades for dysplasia - low, inter
mediate, and high.
METHODS, Pap smears were obtained from 593 women with a cytologic diagnosis
of dysplasia based on the Munich System. Smears were then classified by th
e Bethesda System into LSIL or HSIL. Patients were followed for 2 years eit
her with biopsy or repeat cytology. The initial smears were restained by th
e Feulgen method, and ploidy was evaluated by interactive DNA cytometry.
RESULTS. Of 241 cases of LSIL, 39% were diploid, 57% polyploid, and 4% aneu
ploid, Of 352 cases classified HSIL, 4% were diploid, 17% polyploid, and 79
% aneuploid. After 2 years of follow-up, 2 of 108 patients who were biopsie
d and who were originally classified as diploid progressed to cervical intr
aepithelial neoplasia/ carcinoma in situ (CIN/CIS) whereas 109 of 217 patie
nts who were aneuploid and biopsied were found to have CINIII/CIS.
CONCLUSIONS, The two divisions of the Bethesda System, LSIL and HSIL, corre
lated with ploidy as evaluated by cytometry. Aneuploidy was found to be use
ful to separate cases of HSIL from those of LSIL as defined in the Bethesda
System. Because of the binary division, use of a system with three divisio
ns for dysplasia, such as the Munich II Nomenclature, creates a therapeutic
dilemma because a single diagnostic category (usually the intermediate gra
de) may contain both self-limiting and progressive lesions. DNA cytometry o
f Pap smears was found to be useful as a routine procedure. Cancer (Cancer
Cytopathol) 2001;93:222-228. (C) 2001 American Cancer Society.