ET was reclassified as a cancer of the bone marrow by the World Health Organization in about 2006. Some oncologists do not accept the reclassification, some may not know about it, some just don't want to deal with patients getting emotional about the c-word.

Your life insurance company likely classifies it as cancer, and may deny your application to increase your life insurance on that basis or to charge you higher premiums.

Many cancers now are chronic, in that they are managed by meds vs surgery/chemo/radiation (what my old oncologist called slash/burn/poison). There was a recent article in the Washington Post a few years ago about this. Hopefully people won't be paywalled out:
https://www.washingtonpost.com/health/2023/06/17/cancer-treatment-advances-chronic-disease/