Together there are about 200 different types of cancer[1,2]. To comprehend all these cancers, a general classification is created in the medical circle. This classification help create a common language to define the nature and extent of any given cancer in comparison to other tumors. For example, it can be useful in referencing the cell type in a targeted treatment.In this article, we discuss the traditional view of cancer first; then we introduce you a different view later.
You can read  for the detailed description of cancer. Without further ado, we only introduce you its classification here:
|What's based on?||Description||Categories|
|Cell type||What's the cell and tissue of origin?|
- Carcinomas involve the coating or lining (i.e., epithelial cells) of organ cavities or ducts. Included are the most common cancers of lung, breast, prostate, colon, and skin. Added descriptors such as small cell, squamous, or adeno-, further distinguish tissue of origin.
- Sarcomas develop in the body's connective tissue, such as bone and muscle. This is relatively rare.
- Liquid cancers, including leukemia and lymphomas, originate in cells of the bone marrow or lymph nodes
- Cancers of the brain and spinal cord arise in stem cells of the nervous system
|Grade||How abnormal are the cells under the microscope?|
- Grade I: Cells fairly similar to normal healthy cells of origin, they are "well-differentiated."
- Grade II: Abnormal cell structure and tissue patterns
- Grade III: More marked variation from the normal
- Grade IV: Bizarre, primitive, and poorly differentiated cells
|Stage||How far has the cancer spread?|
- Stage 0: Noninvasive, doesn't extend beyond the superficial cell layer
- Stage I: Penetrates the superficial cell layer to invade the primary organ
- Stage II: Local spread, sometimes to nearby lymph nodes
- Stage III: More severe local and regional spread with lymph node involvement
- Stage IV: Metastasis to distant sites, most often liver, bone, brain, or lungs
|Molecular Signature||Are there specific genes that further characterize and help us understand an individual tumor's behavior?|
- Oncogenes and their proteins that drive growth
- Lost suppressor genes/proteins that keep malignant cells from suicide
- Genes/proteins that enable cancers' distant spread
- Overall multi-gene or chromosome patterns that indicate prognosis
Dr. David B. Agus has taken a different view of cancer. He said that:
Recent findings support this view. As reported in , it says that cancer will increasingly be seen as a disease defined primarily by its genetic fingerprint rather than just by the organ where it originated.
When we see a whole bunch of cells starting to divide uncontrollably in an area, we call that cancer, and depending on the body part in which it happens, we'll call it lung cancer or brain cancer. But, that's not actually what's wrong; that's a symptom of what's wrong.
In Dr. Agus' opinion, cancer is a failure of the system and has two distinctive characteristics:
- Similar appearance
- Cancers all have different genes, but they all look alike.
- There may be fifty different molecular ways to arrive at a particular body "cancer," such as breast, colon, lung, brain, or prostate, but they all appear and act the same way in the end.
- Ability to evolve over time
- Every time a new generation of cancer cells is born, those cells harbor new mutations—mutations that go beyond those already present in the genes that are supposed to regulate growth.
- Just as resistant strains of bacteria can result from antibiotic use, anticancer drugs can produce resistant cancer cells.
He further explained why people are "cancering" (note that a verb instead of a noun is used here to account for its dynamic nature):
- The body has several pathways leading to cancer
- While we may find a way to block one molecular pathway in our attempts to treat the disease, that doesn't mean cancer can't find its way down another path, which it usually does in an efficient fashion, unfortunately.
- The body also has several pathways to repair DNA
- For example, a mutation in BRCA1 and BRCA2 doesn't cause breast cancer. What the BRCA1 and 2 genes do, probably is interrupt the conversation taking place in your body to repair broken DNA. Not until all these efforts to repair DNA fail, will the person has the BRCA genes develop breast cancer.
To summarize, he described cancer in this way:
What keeps cancer under control is a conversation that is happening between your cells, and the language of that conversation is contained in your proteins. For cancer patients, somehow
- The cells are deciding to divide when they shouldn't, not telling each other to die, or telling each other lies.
- All the regulation that is supposed to happen in this conversation is broken.