Tumour development

Most breast cancers start in the epithelial cells (surface cells) of milk ducts, and some in the gland lobules. When the tumour is situated in the ducts or lobules and has not penetrated their cell walls (basement membrane), it is known as a carcinoma in situ - confined locally to the site of onset, e.g. a gland lobule. This is a non-invasive early stage. In this "resting” phase, surgical removal offers a very good chance of curing the disease.

If the tumour cells have penetrated the basement membrane and are growing in the surrounding connective and fatty tissue, this is known as an invasive tumour. This is the actual breast cancer.

Definition of breast cancer:
"Breast cancer means malignant new growth of cells in the duct system and lobules of the female breast, with a high tendency towards lymphogenic and haematogenic metastasis”.*

* Source: Siegenthaler, W.: Lehrbuch der inneren Medizin, Thieme Verlag, Stuttgart, 1984.