Tumor Marker:- Part 1 – Definition of Tumor Markers, Staging and Grading
Definition of Tumor Markers
- Tumor markers are the biochemical or immunological counterparts of the differentiation state of the tumor.
- Tumor markers represent the expression of the substances produced normally by embryogenically related tissues.
- Tumor markers are the substances found in increased concentration in malignancies in:
- Body fluids.
- Body tissues.
- Tumors markers can be measured:
- Tumors markers can be measured by:
- Chemical methods.
- Immunological methods.
- Molecular biological methods.
- An ideal tumor marker should be both specific and sensitive to detect small tumors in the early stages.
- But unlikely this is not the situation.
- These are found in different tumors, even originating from one source.
- These are present in high concentrations in malignancies than the benign tissue.
Advantages of tumor marker
- The tumor markers help diagnose, prognosis, and monitor the tumor.
- Help in the determination of the progression of the disease.
- Help in the monitoring of the tumor after the treatment.
- It can be used for the Screening of the general population.
- These are helpful for the Clinical staging of the tumors.
- Help for the Evaluation of the success of the treatment.
- Very useful for the Detection of the recurrence of the tumor.
- Helpful to decide on the immunotherapy.
Staging and Grading
The latest TNM classification was published by the Union for International Cancer Control (UICC) and the American Joint Committee on Cancer (AJCC) in 2017.
Staging of the tumors:
The most common is the TNM classification. This depends upon the spread of the tumor.
- T = Primary tumor size.
- N = Lymph nodal status is the regional lymph node involvement.
- M = Metastasis of the tumor describes the distant spread of the tumor.
Primary tumor size:
- TX = The Main tumor cannot be measured.
- T0 = Main tumor cannot be found.
- T1 = Size and extent of the tumor.
- T2 = same as above
- T3 = same as above
- T4 = same as above. As the T1 to T4, similarly, the tumor size increases.
Lymph nodes status:
- N0 = There is no tumor infiltration in the near regional lymph nodes.
- N1 to N3 = Indicates the number of lymph nodes involved.
- M0 = No distant metastasis found.
- M1 = Positive for distant metastasis.
Grading of the tumor
- This is the histologic appearance of the tumor cells and how abnormal these tumor cells are seen under the microscope.
- This will indicate how the tumor will grow and spread.
This is the histologic differentiation of the tumor. This may be:
- When the tumor cells and organization are near the normal cells and the tissue.
- These tumor cells grow and spread at a slow rate.
- Moderately differentiated.
- Poorly differentiated. When the tumor cells are abnormal and fast-growing.
The tumors are graded as follows:
- Grade 1, when the tumor cells are near the normal tissue.
- Grade 2, when the tumor cells are slightly away from the normal tissue.
- Grade 3, when the tumor cells grow rapidly and faster.
- Grade 4, when the tumor cells grow more rapidly and abnormal-looking than the normal tissue.
The grades are:
- G1= Well-differentiated and low grade.
- G2 = Moderately differentiated and are intermediate grades.
- G3 = Poorly differentiated and high grade.
- G4 = Undifferentiated and are high grade.
- The latest classification given by the College of Americal Pathologists is followed.
TNM classification objectives are:
- This will help in treatment planning.
- This will give an idea about the prognosis.
- This will evaluate the treatment result.
- It will facilitate the exchange of information between the centers.
- It supports cancer control activities, including cancer registries.
- This will contribute to the investigations of human malignancies. (Source = UICC).