The Who, What, Where, When and Sometimes, Why.

Tumor Size and Staging

A pathologist measures the size of the tumor removed during surgery. The longest length of the tumor in the tissue removed during surgery is reported as the tumor size. Tumor size may be measured under a microscope, especially for small tumors.

Tumor size is related to prognosis (chances for survival). In general, the smaller the tumor, the better the prognosis tends to be [12].

Tumor size is part of breast cancer staging. In the TNM staging system, a “T” followed by a number shows the size of the tumor.

In some cases, the size of the tumor cannot be determined (TX) or a tumor cannot be found (T0).

A diagnosis of carcinoma in situ is classified as Tis.

Tumor size categories

TX: Tumor size cannot be assessed

T0: No tumor can be found

Tis: Carcinoma in situ


Subcategories of Tis:


Tis (DCIS): Ductal carcinoma in situ (DCIS)


Tis (Paget): Paget disease of the breast (Paget disease of the nipple) with no DCIS or invasive breast cancer

T1: Tumor is 2 cm or smaller


Subcategories of T1:


T1mi: Very small tumor (0.1 cm or smaller)


T1a: Tumor is larger than 0.1 cm, but no larger than 0.5 cm


T1b: Tumor is larger than 0.5 cm, but no larger than 1 cm


T1c: Tumor is larger than 1 cm, but no larger than 2 cm

T2: Tumor is larger than 2 cm, but no larger than 5 cm

T3: Tumor is larger than 5 cm

T4: Tumor is any size, but has spread beyond the breast tissue to the chest wall and/or skin


Subcategories of T4:


T4a: Tumor has spread to the chest wall


T4b: Tumor has spread to the skin, but isn’t inflammatory breast cancer


T4c: Tumor has spread to both the chest wall and skin


T4d: Inflammatory breast cancer

Adapted from American Joint Commission on Cancer materials [30].

The following is a 3D interactive model showing the stages of breast cancer from 0 to IV. Click the arrows to move through the model to learn more about breast cancer.

 Updated 03/12/24