Northern Thai women with high grade squamous intraepithelial lesion on cervical cytology have high prevalence of underlying invasive carcinoma.

The aim of this study was to determine the underlying pathology of women with high grade squamous intraepithelial lesion (HSIL) on cervical cytology. A total of 681 women with HSIL cytology undergoing colposcopic examination at Chiang Mai University Hospital (CMUH) between January 2000 and December 2005 were evaluated for the underlying cervical pathology. The final pathology was diagnosed from the most severe lesions obtained by punch biopsy, loop electrosurgical procedure, cold knife conization or hysterectomy. Underlying high grade cervical lesions including cervical intraepithelial neoplasia grade 2, 3 and adenocarcinoma in situ were noted in 502 (73.7%) women. Invasive cervical carcinoma was identified in 141 (20.7%). The remaining 38 (5.6%) had either low grade or no intraepithelial lesions. No significant difference in the prevalence of underlying high grade and invasive lesions was noted between women with cytologic diagnosis of HSIL from CMUH and other hospitals. In conclusion, northern Thai women with HSIL cytology are at significant risk of having underlying severe cervical lesions, and especially invasive carcinoma which is detected in approximately one-fifth of the cases.