Why wouldnt they give me a better explanation of cancer in situ?

On the verge of canc: Carcinoma in-situ is a lesion, often in the uterine cervix, that is cancer in the epithelial lining but has not gone deeper into the tissue. If removed, the treatment is curative. If left untreated, there is considerable risk of developing invasive cancer that can cause death. The lesion in cervix is usually related to hpv infection.

Pre-cancerous state: Carcinoma in situ is pre-cancer state- or stage 0- a very early stage of cancer in which the tumor is confined to the structure of the organ where it first developed. The disease has not invaded other parts of the organ. Most in situ carcinomas are highly curable. In breast for instance- it is contained within the duct or the lobule of the breast and not invading beyond the duct /lobule.

"In Situ" means: "in place" but really means "it does not invade". In situ has different implications for different organs, i.e., breast versus bladder, versus cervix. Give them another try: ask what does it mean, does it always lead to invasive cancer, what are my options?