An invasive, or infiltrating, carcinoma refers to a cancer that has invaded beyond the confines of the ducts and lobules in the breast. This is different from carcinoma in situ, which has not invaded the surrounding breast tissue.
The vast majority of invasive carcinomas are called invasive ductal carcinomas, but also may be referred to as: invasive mammary carcinoma, not otherwise specified (NOS) and invasive carcinoma, no special type (NST). These carcinomas account for approximately 65-75% of invasive cancers.
The remainder of invasive carcinomas are most often referred to as “special types.” The most common of these special types is called ‘invasive lobular carcinoma,” which usually accounts for approximately 15% of invasive carcinomas. (In the future, check the SBPC Library for more information about invasive lobular carcinoma and other less-common invasive breast cancers.)
Grading invasive carcinomas
Invasive carcinoma of the breast is usually graded, and the grade of the cancer has significance in terms of your prognosis. The most commonly used grading scheme is the modified Scarff-Bloom-Richardson grade, or Nottingham grade.
There are three grades: I, II, and III. The grade of the invasive cancer is based on:
- How much the cancer resembles more normal breast tissue (referred to as “amount of tubule formation”)
- How atypical the cells look (referred to as “nuclear pleomorphism”)
- How fast the cancer is growing (referred to as “mitotic rate”)
The pathologist scores these three features and comes up with a number that you may see in your report as your overall score (from 3-9). The scores correlate to the three grades as follows:
- A score of 3-5 = Grade I (or well differentiated)
- A score of 6-7 = Grade II (or moderately differentiated)
- A score of 8-9 = Grade III (or poorly differentiated)
The size of your invasive cancer is important in determining your breast cancer stage. Learn more. Once the pathologist has determined that you have invasive cancer, it is the size of your invasive cancer and not in situ carcinoma that determines your stage. Often your tumor will have invasive cancer and in situ cancer, but the amount of carcinoma in situ should not be included in that size.
All invasive cancers of the breast should be tested for prognostic and predictive markers, including estrogen and progesterone receptors and HER2 overexpression. Unfortunately, there are many ways of determining if your cancer is estrogen- or progesterone-receptor positive or negative, so it is important to understand what method your pathologist uses. The rules for determining the HER2 status of your cancer have recently changed and will be discussed in the SBPC Library.
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