Primary tumor (T) categories:

Primary tumor (T) categories:
TX: Primary tumor cannot be assessed.
T0: No evidence of primary tumor.
Tis: Carcinoma in situ (DCIS, LCIS, or Paget disease of the nipple with no associated
tumor mass)
T1 (includes T1a, T1b, and T1c): Tumor is 2 cm (3/4 of an inch) or less across.
T2: Tumor is more than 2 cm but not more than 5 cm (2 inches) across.
T3: Tumor is more than 5 cm across.
T4: Tumor of any size growing into the chest wall or skin. This includes inflammatory
breast cancer.


Nearby lymph nodes (N; based on looking at them under a microscope):
Lymph node staging for breast cancer has changed as technology has evolved. Earlier
methods were useful in finding large deposits of cancer cells in the lymph nodes, but
could miss microscopic areas of cancer spread. Newer methods have made it possible to
find smaller and smaller deposits of cancer cells. Experts haven't been sure what to do
with the new information. Do tiny deposits of cancer cells affect outlook the same way
that larger deposits do? How much cancer in the lymph node is needed to see a change in
outlook or treatment?
These questions are still being studied, but for now, a deposit of cancer cells must contain
at least 200 cells or be at least 0.2 mm across (less than 1/100 of an inch) for it to change
the N stage. An area of cancer spread that is smaller than 0.2 mm (or less than 200 cells)
doesn't change the stage, but is recorded with abbreviations that reflect the way the
cancer spread was detected. The abbreviation "i+" means that a small number of cancer
cells (called isolated tumor cells) were seen in routine stains or when a special type of
staining technique, called immunohistochemistry, was used.
The abbreviation "mol+" is used if the cancer could only be found using a technique
called RT-PCR. RT-PCR is a molecular test that can find very small numbers of cells that
cannot be seen even using special stains. However, this test is not often used for finding
breast cancer cells in lymph nodes because the results do not influence treatment
decisions.
If the area of cancer spread is at least 0.2 mm (or 200 cells), but still not larger than 2
mm, it is called a micrometastasis (one mm is about the size of the width of a grain of
rice). Micrometastases are counted only if there aren't any larger areas of cancer spread.
Areas of cancer spread larger than 2 mm are known to affect outlook and do change the
N stage. These larger areas are sometimes called macrometastases, but may just be called
metastases.
NX: Nearby lymph nodes cannot be assessed (for example, if they were removed
previously).
N0: Cancer has not spread to nearby lymph nodes.
· N0(i+): Tiny amounts of cancer are found in underarm lymph nodes by using either
routine or special stains. The area of cancer spread contains less than 200 cells and is
smaller than 0.2 mm.
· N0(mol+): Cancer cells cannot be seen in underarm lymph nodes (even using special
stains), but traces of cancer cells were detected using RT-PCR.
N1: Cancer has spread to 1 to 3 axillary (underarm) lymph node(s), and/or tiny amounts
of cancer are found in internal mammary lymph nodes (those near the breast bone) on
sentinel lymph node biopsy.

· N1mi: Micrometastases (tiny areas of cancer spread) in 1 to 3 lymph nodes under the
arm. The areas of cancer spread in the lymph nodes are 2 mm or less across (but at
least 200 cancer cells or 0.2mm across).
· N1a: Cancer has spread to 1 to 3 lymph nodes under the arm with at least one area of
cancer spread greater than 2 mm across.
· N1b: Cancer has spread to internal mammary lymph nodes, but this spread could only
be found on sentinel lymph node biopsy (it did not cause the lymph nodes to become
enlarged).
· N1c: Both N1a and N1b apply.
N2: Cancer has spread to 4 to 9 lymph nodes under the arm, or cancer has enlarged the
internal mammary lymph nodes (either N2a or N2b, but not both).
· N2a: Cancer has spread to 4 to 9 lymph nodes under the arm, with at least one area of
cancer spread larger than 2 mm.
· N2b: Cancer has spread to one or more internal mammary lymph nodes, causing
them to become enlarged.
N3: Any of the following:
N3a: either
· Cancer has spread to 10 or more axillary lymph nodes, with at least one area of
cancer spread greater than 2mm, OR
· Cancer has spread to the lymph nodes under the clavicle (collar bone), with at least
one area of cancer spread greater than 2mm.
N3b: either:
· Cancer is found in at least one axillary lymph node (with at least one area of cancer
spread greater than 2 mm) and has enlarged the internal mammary lymph nodes, OR
· Cancer involves 4 or more axillary lymph nodes (with at least one area of cancer
spread greater than 2 mm), and tiny amounts of cancer are found in internal
mammary lymph nodes on sentinel lymph node biopsy.
· N3c: Cancer has spread to the lymph nodes above the clavicle with at least one area
of cancer spread greater than 2mm.