Understanding Your Breast Tumor Size

Different sizes

Finding out the exact size of your breast cancer tumor affects the staging of your cancer and your treatment decisions. Do you know what size your tumor is?  

Breast cancer is staged by the TNM System: Tumor size, node status, and metastasis. This is also called the AJCC staging system. Tumor Size is divided into four classes:

  1. T-1 is from zero to two centimeters. This is less than an inch in diameter, up to four-fifths of an inch—the size of a peppercorn up to the size of a black-eyed pea.
  1. T-2 is from two to five centimeters. This range is from about four-fifths of an inch to two inches in diameter—the size of a cranberry to the size of a walnut.
  2. T-3 is greater than five centimeters. This is larger than two inches in diameter—the size of a lime.
  3. T-4 is a tumor of any size that has broken through (ulcerated) the skin or is attached to the chest wall.

Measuring Tumor Size

Tumor sizes are measured by a radiologist using a mammogram or an ultrasound image taken of your breast. But not all tumors are simple, round shapes that are easy to measure. For example, the tumor could be elongated like a baked potato and the image could be at an angle in which the radiologist can't see all of the dimensions. And some tumors even have irregular edges so it's hard to estimate the total diameter of the tumor. 

Tumor Size & Staging

Tumor size, lymph node status, and metastasis are combined to calculate the stage of your breast cancer with the TNM system.

This important information is used to assess your options for surgery as well as local and systemic therapies. Here's how it works:

T = Tumor Size: T1 = 0-2 cm, T2 = 2-5cm, T3 = 5cm, T4 = ulcerated or attached

N = Node Status: N0 = clear or negative nodes, N1 = cancerous or positive nodes

M = Metastasis: M0 = no spread of tumor, M1 = tumor has spread

Stage 0: Pre-cancerous

Stage 1  T-1,  N-0,  M-0

Stage 2: Can be any of these combinations:

  • T-1, N-1, M-0.  Notation: T1 N0 M0
  • T-2, N-0 or N1, M-0 Notation: T2 N0 M0 or T2 N1 M0
  • T-3, N-0, M-0 Notation: T3N0M0

Stage 3: Can be any of these combinations:

  • T-Any, N-1, M-0  Notations: T1 N1 M0, T2 N1 M0, T3 N1 M0, T4 N1 M0
  • T-3, N-0 or N-1, M-0 NotationS: T3 N0 M0, T3 N1 M0
  • T-4, N-0, M-0 Notations: T4 N0 M0

Stage 4:

  • T-Any size, N-Any status, M-1.
  • Notations: T1 N0 M1, T1 N1 M1, T2 N0 M1,T2 N1 M1,T3 N0 M1,T3 N1 M1, T4 N0 M1,T4 N1 M1


Cancer Staging, National Cancer Institute, Updated January 6, 2015.

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