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Understanding Cancer

How is Cancer Diagnosed?

Diagnosing cancer involves the use of a variety of tests that provide details about abnormal cells, which may have been detected through routine medical examinations, self-examination, or reported symptoms. More information about these cells must be gathered in order to identify them as malignant (cancerous) or non-malignant (non-cancerous), and if they are malignant, to determine how serious (aggressive) the particular cancer cells are. Aggressive cancers grow and spread more quickly than less-aggressive or “indolent” cancers. There are many types of tests specifically designed to evaluate cancer:

  • A pathology report is based on observation of abnormal cells under a microscope.
  • Diagnostic imaging involves visualization of abnormal masses using high-tech machines that create images, such as x-rays, computed tomography (CT), positron emission test (PET), magnetic resonance imaging (MRI), and combined PET/CT.
  • Blood tests measure substances in the blood that may indicate how advanced the cancer is or other problems related to the cancer.
  • Tumor marker tests detect substances in blood, urine, or other tissues that occur in higher than normal levels with certain cancers.
  • Special laboratory evaluation of DNA involves the identification of the genetic make-up—the DNA—of the abnormal cells.

Cancer Staging

Cancer staging describes how far cancer has spread to other organs or to other systems in your body. Staging helps guide treatment in coordination other factors, including your general health, your own preference, and the results of biochemical tests. So while the stage is important it is not everything.

The concept of stage is applicable to almost all cancers except for most forms of leukemia. Since leukemias involve the blood, they are not anatomically localized like other cancers. A few forms of leukemia do have staging systems which reflect various measures of how advanced the disease is. For most solid tumors, there are two related cancer staging systems, the Overall Stage Grouping, and the TNM system.

Roman Numeral Staging
In this staging system, your disease is grouped into four stages denoted by Roman numerals I through IV, or are classified as "recurrent." In general, stage I cancers are small localized cancers that are usually curable, while stage IV usually represents inoperable or metastatic cancer. Stage II and III cancers are usually locally advanced and/or with involvement of local lymph nodes. Actually, these stages are defined precisely, but the definition is different for each kind of cancer. In addition, it is important to realize that the prognosis for a given stage also depends on what kind of cancer it is, so that a stage II non-small cell lung cancer has a different prognosis from a stage II cervical cancer.

TNM Staging
In the TNM system, TNM stands for Tumor, Nodes, and Metastases. Each of these is categorized separately and classified with a number to give the total stage. Thus a T1N1M0 cancer means the patient has a T1 tumor, N1 lymph node involvement, and no distant metastases. Of course the definitions of T, N and M are specific to each cancer, but it is possible to give a general idea of what they mean.

T: Tumor - T classifies the extent of the primary tumor, and is normally given as T0 through T4. T0 represents a tumor that has not even started to invade the local tissues. This is called "In Situ". T4 on the other hand represents a large primary tumor that has probably invaded other organs by direct extension and is most often inoperable.

N: Lymph Nodes - N classifies the amount of regional lymph node involvement. It is important to understand that only the lymph nodes draining the area of the primary tumor are considered in this classification. Involvement of distant lymph nodes is considered to be metastatic disease. The definition of just which lymph nodes are regional depends on the type of cancer. N0 means no lymph node involvement while N4 means extensive involvement. In general, more extensive involvement means some combination of more nodes involved, greater enlargement of the involved nodes, and more distant (But still regional) node involvement.

M: Metastasis - M is either M0 if there are no metastases or M1 if there are metastases.
As with the Roman Numeral system, the exact definitions for T and N are different for each different kind of cancer.

As you can see, the TNM system is more precise than the I through IV system and certainly has a lot more categories. The two systems are actually related. The I through IV groupings are actually defined using the TNM system. For example, stage II non-small cell lung cancer means a T1 or T2 primary tumor with N1 lymph node involvement, and no metastases (M0).