By ProPath Women’s Health Staff
As a result of our evolving understanding of the pathobiology and behavior of cervical cancer precursors, there have been many changes in the nomenclature of these lesions, and multiple different classification schemes exist (Table 1). At ProPath, we use standardized, up-to-date reporting terminology for cervical cancer precursor lesions. Our classification system improves communication and makes clinical decision making more straightforward.
Low-grade squamous intraepithelial lesion (LSIL, CIN 1, mild squamous dysplasia)
This category is believed to represent a productive human papillomavirus infection of the cervical squamous epithelium which, in most cases, is self-limited and carries a low risk of subsequent invasive cancer. These lesions may be flat or exophytic (condyloma acuminata). This category encompasses entities that were previously designated as “koilocytic atypia”, “flat condyloma”, or “koilocytosis.”
High-grade squamous intraepithelial lesion (HSIL, CIN 2, moderate squamous dysplasia)
In the WHO/CIN classification scheme, CIN 2 lesions are an intermediate in a stepwise histological progression from CIN 1 to invasive cancer. However, evidence suggests that this stepwise model may not accurately reflect the underlying biology. Rather than a single process, the histological changes of cervical pre-cancer probably represent two distinct biological entities—one a productive viral infection (LSIL) and the other a true neoplastic process confined to the epithelium. Many lesions in the HSIL/CIN 2/moderate dysplasia category are of the latter type, and carry a substantial risk of progression to invasive cancer if untreated.
High-grade squamous intraepithelial lesion (HSIL, CIN 3, severe squamous dysplasia/carcinoma in situ)
These lesions are believed to represent true neoplastic processes that are confined to the epithelium. In the past, severe dysplasia and carcinoma in situ were classified separately, but this is no longer considered a necessary or reliable distinction. These lesions carry a substantial risk of progression to invasive squamous cell carcinoma if untreated.
Difficult cases
Cervical biopsies occasionally contain atypical areas that are difficult to classify, most often because the concerning focus is very small or has superimposed reactive changes. We understand that the definitive classification of cervical biopsies greatly simplifies clinical decision making, and in the majority of cases, we are able to make a definitive diagnosis. Difficult cases are brought to our intradepartmental consensus conference, and immunohistochemical stains are used as needed. In those few cases where we cannot definitively classify a lesion, descriptive terminology is used to explain the histological findings and, when necessary, provide recommendations for follow-up testing. We are available to discuss these challenging cases with you at any time.