CIN 3: the role of lesion size in invasion.

OBJECTIVE

To define the relation between the size of a CIN 3 lesion (measured histologically) and invasive squamous carcinoma.

DESIGN

Measurement of CIN 3 by computerized planimetry of histological sections from 39 cone biopsies containing microinvasive cancer. Comparison with previous measurements of CIN lesions, associated with different grades of dyskaryosis.

RESULTS

Microinvasive carcinoma of the cervix is associated with extensive CIN 3 on the surface and in endocervical crypts. The mean size of CIN 3 lesions showing microinvasion is seven times greater than that for severe dyskaryosis without invasion, (P less than 0.0001) and a 100-fold greater than with mild dyskaryosis (P less than 0.00001).

CONCLUSION

Invasive squamous carcinoma of the cervix arises in large CIN 3 lesions and these are associated usually with severe dyskaryosis. We propose a model for the development of high-grade precancer as a small focus within low grade precancer which then undergoes expansion in size, accompanied by apparent progression in cytological grade.