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Part 2
Grading
and Staging of Cancer
TNM
Classifications
Grading and staging of neoplasms are attempts
to describe the degree of malignancy and dissemination of
the cancer. These procedures are of great importance in comparing
the results of various forms of therapy.
Understanding of the systems of grading and
staging of cancers can be of benefit to coders. If the diagnosis
given is ambiguous, review of the medical record for staging
or grouping of the tumor can assist in determining if local
or distant metastasis is present, ultimately resulting in
more precise coding of malignancies.
Cancer is graded on the differentiation
of the tumor cells and the number of mitoses present. These
are thought to be correlated with the ability of the tumor
to grow and spread. Histologic grading determines the degree
of loss of normal cellular differentiation and function of
tumor cells, varying from Grade I (very well differentiated)
to Grade IV (undifferentiated). Grading is of some value in
determining prognosis in soft tissue sarcoma, transitional
cell carcinoma of the bladder, astrocytoma, and chondrosarcoma.
It is of little prognostic value in melanoma and osteosarcoma.
Cancers are staged with respect to their
size, amount of local spread, and whether or not blood-borne
metastasis has occurred. These factors are used to indicate
the extension of cancers as they appear (or do not appear)
on clinical examination prior to beginning definitive therapy.
In some malignancies, such as squamous cell carcinoma of the
cervix, staging is done by clinical examination alone. In
others, such as adenocarcinoma of the colon, stage is determined
by findings in the resected surgical specimen.
Duke’s Classification, which was
devised 60 years ago, describes the pathologic stages of tumor
involvement in carcinoma of the colon and rectum. It includes
four classifications:
|
Class A: |
Limited to mucosa
and submucosa |
|
Class B: |
Penetration
of the entire bowel wall and serosa or pericolic fat |
|
Class C: |
Class A and
B and invasion into the regional draining lymph
node system |
|
Class D: |
Advanced and
widespread regional involvement (metastasis) |
The standardized staging of a tumor at the time
of diagnosis is important for determining the prognosis and
planning treatment. The American Joint Committee on Cancer
(AJCC) has developed a classification system based on the
premise that cancers of similar histology or site of origin
share similar patterns of growth and extension. This classification
system can easily be incorporated into a form for the staging
of tumors.
TNM Staging is used clinically to indicate
the extension of cancer prior to beginning definitive therapy.
The manner in which the staging is accomplished, clinical
examination or pathological examination of a specimen, must
be documented. The TNM system allows for numerical assessment
of the following:
|
T |
Extent of the primary tumor |
|
N |
Absence or presence and extent
of regional lumph node metastasis |
|
M |
Absence or presence of distant
metastases |
The significance of these marker points differs
for tumors of different sites and histologic types. Therefore,
the marker points of T, N, and M must be defined for each
type of tumor in order to be valid and have maximum significance.
For example, TNM classification and staging of cancer of the
colon and rectum is shown to the right.
In certain types of tumors, such as lymphoma
and Hodgkin’s, a different classification system is usually
used which reflects the natural history of this type of tumor
spread. Both histologic grading and clinical staging are relevant
to the choice of treatment in lymphoma and Hodgkin’s.
Traditional staging does not take into account
the biology or aggressiveness of a tumor and may not allow
differentiation of risk groups. Because of this, specific
pathologic characteristics are added into the prognostic evaluation
for certain tumors. For example, estrogen and receptor assays
and proliferative index are considered in staging breast cancer.
As these characteristics are better understood and become
standardized, they may allow identification of patients with
a poorer prognosis earlier in the course of disease when more
aggressive treatment may be beneficial.
Grading and classification and stage-grouping
are a method of designating the extent of a cancer and are
related to the natural course of a particular type of cancer.
They are intended to provide a way by which information can
be easily communicated, assisting in decisions regarding treatment
and determining prognosis. They also provide a mechanism for
comparing cases, particularly in regard to the results of
different therapeutic procedures.
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TNM Classification
Carcinoma of Colon and Rectum
|
Primary
Tumor (T)
|
| TX |
Primary
tumor cannot be assessed |
| T0 |
No
evidence of primary tumor |
| Tis |
Carcinoma
in situ |
| T1 |
Tumor
invades submucosa |
| T2 |
Tumor
invades muscularis propria |
| T3 |
Tumor
invades through the muscularis propria into
the subserosa or into the nonperitonealized
pericolic or perirectal tissue |
| T4 |
Tumor
invades into the visceral peritoneum or
directly invades other organs or structures
|
|
Regional
Lymph Nodes (N)
|
| NX |
Regional
lymph nodes cannot be assessed |
| N0 |
No
regional lymph node metastasis |
| N1 |
Metastasis
in one to three periocolic or perirectal
lymph nodes |
| N2 |
Metastasis
in four or more pericolic or perirectal
lymph nodes |
| N3 |
Metastasis
in any lymph node along the course of a
named vascular trunk
|
|
Distant
Metastasis (M)
|
| MX |
Presence
of distant metastasis cannot be assessed |
| M0 |
No
distant metastasis |
| M1 |
Distant
metastasis
|
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Stage
Grouping
|
|
|
T |
N |
M |
| Stage
0 |
Tis |
N0 |
M0 |
| Stage
I |
T1
T2 |
N0
N0 |
M0
M0 |
| Stage
II |
T3
T4 |
N0
N0 |
M0
M0 |
| Stage
III |
Any
T
Any T |
N1
N2, N3 |
M0
M0 |
| Stage
IV |
Any
T |
Any
N |
M1
|
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Part 1: Neoplasms
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