Classification of invasive breast cancers

The most commonly used classification of invasive breast cancers divides them into ductal and lobular types. This classification was based on the belief that ductal carcinomas arose from ducts and lobular carcinomas from lobules. We now know that invasive ductal and lobular breast cancers both arise from the terminal duct lobular unit, and this terminology is no longer appropriate. Some tumours show distinct patterns of growth and cellular morphology, and on this basis certain types of breast cancer can be identified. Those with specific features are called invasive carcinomas of special type, while the remainder are considered to be of no special type. This classification has clinical relevance in that certain special type tumours have a much better prognosis than tumours that are of no special type.