Breast Cancer Size

Breast cancer size is measured at the tumor’s widest point.

The size of a breast cancer is the measurement of the tumor at its widest point. Doctors measure cancers in centimeters (cm) or millimeters (mm).

The size of the cancer used to be considered extremely important when determining breast cancer stage. In 2018, the American Joint Committee on Cancer (AJCC) updated the breast cancer staging system, so other factors such as hormone receptor status and HER2 status are considered as well. This means that the size of the cancer, although still important when determining stage, is not as important as it once was.

For example, in the past, a breast cancer that was larger than 5 centimeters would likely be classified as stage IIIA. Today, if the cancer were the same size and also hormone receptor-positive, it would likely be classified as stage IB.

When trying to visualize the size of a cancer, it can help to think of common items and foods:

1 mm is about the size of a pencil point
5 mm is about the size of a pencil eraser
10 mm or 1 cm is about the size of a pea
20 mm or 2 cm is about the size of a peanut
50 mm or 5 cm is about the size of a lime
60 mm or 6 cm is about the size of an egg
70 mm or 7 cm is about the size of a peach
100 mm or 10 cm is about the size of a grapefruit

— Last updated on September 27, 2023 at 6:35 PM