How to Grade and Identify the Stage of a Tumor
Cancer is a disease of the cell in which the normal mechanisms of control of growth and proliferation are disturbed. This results in distinctive morphologic alterations of the cell and aberrations in tissue patterns.
The malignant cell is able to invade the surrounding tissue and regional lymph nodes. Primary cancer usually has a predictable natural history and pattern of spread.
Metastasis is the secondary growth of the primary cancer in another organ. The cancer cell migrates through a series of steps to another area of the body. This is the reason that cancer cannot always be cured by surgical removal alone. Most patients die as a result of metastases rather than progression of the primary cancer. Metastasis begins with local invasion followed by detachment of cancer cells that disseminate via the lymphatics and blood vessels and eventually establish a secondary tumor in another area of the body. Lymph nodes are often the first site of distant spread.
Staging is necessary at the time of diagnosis to determine the extent of disease (local versus metastatic), to determine prognosis, and to guide proper management.
The American Joint Committee of Cancer (AJCC) has developed a simple classification system (TNM) that can be applied to all tumor types. It is a numerical assessment of tumor size (T), presence or absence of regional lymph node involvement (N), and presence or absence of distant metastasis.
T – Primary Tumor
Tx – Primary tumor is unable to be assessed
T0 – No evidence or primary tumor
Tis – Carcinoma in situ
T1, T2, T3, T4 – Increasing size and/or local extent of primary tumor
N – Presence or absence or regional lymph node involvement
Nx – Regional lymph nodes are unable to be assessed
N0 – No regional lymph node involvement
N1, N2, N3 – Increasing involvement of regional lymph node
M – Absence or presence or distant metastasis
Mx – Unable to assess
M0- Absence of distant metastasis
M1 – Presence of distant metastasis
No standard evaluation exists for all cancers. Work-up depends on the patient, tumor type, symptoms, and medical knowledge of the natural history that cancer.
It is important that staging is done correctly mainly for the reason that the disease stage will determine the treatment the patient will receive. So, errors in staging might lead to the inappropriate treatment, thus, the patient’s rate of survival will likely be lessened. But correct staging is not an easy task. There are two main reasons why pathologic staging (tissue sections are examined) can become problematic: random tissue sampling and visual discretion, or the ability to recognize single cancerous cells when surrounded or intermixed with ones that are healthy on a slide. With random sampling, cherry-picked sections of the lymph nodes could mean that the slices happen to be healthy cells or that it might not have included the cancerous cells.
Not to fret, as fresh and highly-sensitive staging methods are being developed.
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