Have you been through my previous blogs. If not, then go right away, what are you doing here? Go and you can also win a chance to take your family to Jurassic period as I have repaired my time machine.
Just kidding. Even I can’t go there. Poor me.
Well, forget that. What I wanted to say, if you have read my previous blogs then you know how many times I have talked about cancer in some of the articles. One of them is solely based on cancer i.e. Lymphoma.
So, this time I will be talking about some general concepts about them. Which are:
- What is carcinoma vs sarcoma or benign tumor vs malignant?
- What is a grade or stage of tumor means?
- What are some most common metastases regions?
So, without further ado, lets dig into it.
What is Carcinoma vs Sarcoma?
- Tumor that has originated from epithelial tissue (see A1).
- Eg, Epithelial tissue that lines internal organs like liver i.e. hepatocellular carcinoma, the epithelial tissue of skin i.e. basal cell carcinoma (most common skin cancer) or squamous cell carcinoma (2nd most common skin cancer).
- Carcinoma is the most common type of cancers.
- Tumor that has mesenchymal(A2) origin.
- Cancer that originates in bone i.e. osteosarcoma, fat i.e. liposarcoma, cartilage i.e. chondrosarcoma or blood vessels i.e. angiosarcoma etc.
- These are not much common.
A1: Epithelium– It is a dense tissue where cells are tightly packed. It protects, absorbs, secretes, filters etc. It is one of the 4 main tissues found in humans. Others are- Connective tissue, muscle tissue and nervous tissue. Epithelium rest on basement membrane (BM). What is BM? Well, here you go:
- Non-cellular structure beneath epithelium made up of collagen (protein for strength), glycoproteins like laminin which itself is secreted by epithelial cells.
- BM provides attachment of epithelium with connective tissue
- BM is also needed for structural support of epithelial cells.
- BM filters substances from blood before reaching it as epithelium itself doesn’t have any blood vessels.
A2: Mesenchyme– It is a loose, undifferentiated connective tissue. It forms many structural components like cartilage, bone, muscle, lymph and blood vessels. Simply saying, musculoskeletal system and circulatory system.
Q1: Is mesenchyme and mesoderm same?
A1: No. Mesoderm is one, particularly middle, of the three germ layers (others are ectoderm and endoderm from outside to inside). These germ layers form everything in embryo. Moreover, it is the mesoderm that later forms mesenchyme along with endocrine glands, urogenital structures like fallopian tube in female and testes in males and etc.
What is benign or malignant?
First, you should know, a cancer cannot be benign. Benign term is used for tumor. Tumor can be cancerous (malignant) or noncancerous (benign).
Benign: As I said, it is the growth of cells that is not a cancer, yet. In this state,
- Cells have low mitosis i.e. division of cells. Means, their growth is still controlled in a manner.
- Do not show metastases i.e. spreading from one part to other and necrosis i.e. death of tissue.
- Cells are well-demarcated i.e. they can be easily defined from their surrounding cells.
- Cells are well-differentiated i.e. still have normal cell features/appearances.
- Low grade tumors are counted.
Malignant: This is more aggressive and lethal tumor.
- Cells grow in accelerated, uncontrolled manner(Q2) and barely perform apoptosis(A3).
- Cells break away from their primary location and after travelling through circulatory system, they target a new location and grow there. Simply, show metastasis.
- Cancer cells are poorly differentiated. Means, here tumor cells are disorganised unlike normal cells when looked through a microscope.
- In this, high grades tumor are counted.
But what are high grade and low grade tumor. Wait for now, your question will be answered. But before that…
Q2: How does cancer cells growth becomes uncontrolled?
A2: Normal cells have genetic material that contains information about their growth, functions etc which they perform in controlled and regular manner. Cancer cells… well, they also have genetic material but because of any mutation in DNA, their original and normal role is turned off and now they perform without any worldly care. They become like an employee who has won best employee of the year but now has lost any kind of suppression causing damage to himself/herself, others i.e. other tissue and company i.e. body as a whole. Also can make others like him/her too.
Cause- Genetic mutation can be caused by high energy radiations like X-ray or UV rays, carcinogens like tobacco in cigarettes or cigars, asbestos found in cement, alcohol that in body breaks down by alcohol dehydrogenase from ethanol into acetaldehyde in liver which is a carcinogen. These are some of the common areas where carcinogens could be found. Any substance that increases cancer risk is a carcinogen.
The genes that are affected are:
- Tumor suppressor gene- These genes, as the name says, controls cellular growth and division. Mutation in these can lead to encouraged growth.
- Eg, BRCA1/2 (chromosome 17) gene mutation that can lead to BReast CAncer.
- Proto-oncogenes- Involved in normal cell division and differentiation. Mutation in these can lead to oncogene formation which is a carcinogen.
- Eg, HER2 (chromosome 17) proto-oncogene that is involved in growth of breast as this gene make HER2 receptors that are present on breast cells for cell’s growth regulation and repair.
- DNA repair genes- DNA repair genes, as the name says, repair genes. This repairing is very crucial as we know how vast our genetic material is (each cell contains around 2 meter long DNA. You can calculate yourself but let me know if you need my help.). The accidents are pretty obvious if this huge length is being copied by our tiny cellular components.
- Eg, TP53 (chromosome 17) is a very important transcription factor that is used in many functions. Some of them are- DNA repair (well, why not?), induces apoptosis, arrests cell growth etc.
- Because of its variety of functions, you can think it can cause variety of cancers. To name, Li-Fraumeni syndrome is a risk for many cancers like osteocarcinoma, acute leukemia, breast and brain cancer etc which is associated with Tumor Protein 53 mutation.
A3: Apoptosis- It is programmed cell death that vanishes unwanted cells. It can be considered as a form of senile death of old cells. Apoptosis initiates at chromatin condensation -> nuclear degradation -> apoptotic body formation from degraded chromatin, protein, organelles etc.
For this process, you should know about caspases.
Caspases: Caspase is a combined name of cysteine-aspartic proteases. (Enzymes are proteins except ribozyme, and has suffix- ase.)
- These are very important proteolytic enzymes that controls cell death.
- There are types of caspases, eg, initiator caspase that initiates cell death process and caspase-3 that cleaves alpha-tubulin and fodrin (proteins for plasma/cell membrane).
- Present as zymogen (inactive precursors of proteolytic enzymes) and needs activation before apoptosis.
- Disintegrates most of the cellular components like cytoskeleton proteins, endoplasmic reticulum, golgi apparatus and nucleus.
Now let us get onto…
What is Grade of cancer means?
Grade: It is the degree that tells us how much cell is differentiated from its healthy cell. It also states about their aggressiveness i.e. how much they divide and grow.
There are 3 grades.
- Grade 1- Lowest grade. Cells are well-differentiated with somewhat normal growth.
- Grade 2- Cells are slightly abnormal with faster than normal growth.
- Grade 3- Poor differentiation with very aggressive growth.
For simplicity, grades can be called as low grade and high grade with well-differentiation and undifferentiating respectively.
Stage: Unlike the appearance of cancer cells by grading system, it states us about their size and localization that how much they have spread.
- Stage 0 or in-situ: In this, cells are abnormal but are restricted to their original location and not cancerous till now.
- Stage I-III: Cancer is growing and still not spread or has spread to a nearby tissue.
- Stage IV: Cancer has become metastatic and has spread to distant organs and tissues.
TNM staging system: This system is one of the most used and widely accepted system describing the spread of tumor. Its quiet simple. Let us understand with an example.
Suppose we are given a cancer with stage T4N2M1.
Now T is Tumor size.
- It ranges from TX -> T0 -> T1 -> T2 -> T3 -> T4.
- TX and T0 are when tumor can’t be measured and found respectively.
- T1-T4 means the tumor is increasing.
N is Node that is involved with cancer.
- It ranges from NX -> N0 -> N1 -> N2 -> N3.
- Same as T, NX and N0 means the tumor is can’t be assessed in lymph nodes and has not been found respectively.
- More lymph nodes are involved with increased staging.
M is Metastases stage.
- It ranges from MX -> M0 -> M1.
- Where MX and M0 has similar meaning.
- M1 means that metastases are seen. No further staging is needed as it is enough to tell us if cancer will spread elsewhere or not and how dangerous it can be.
Q3: Which provides better prognosis of cancer, stage or grade?
A3: Stage is considered as better prognostic measure. Think this, a cancer that is low-stage with high-grade is weaker than high-stage with low-grade cancer.
What is metastasis and its common sites?
Metastasis: As I said, it is the spreading of cancer from one site to another. The cancer from where the metastasis is occurring is called 1o tumor and to where it is going can be called 2o tumor.
- 1o tumor from lungs, breast, kidney or colon cancer mostly spreads to brain. You may find it interesting to know that almost half of the brain cancers are metastatic.
- 1o tumor from colon most commonly metastasises to liver. Liver is also 2o target of stomach, pancreas and regional lymph nodes.
- 1o tumor of prostate, breast, lung, thyroid and kidney mostly spread to bone. Just like brain cancer, bone cancer is also caused by metastasis excessively.
- 1o tumor of breast, kidneys, colon, rectum spreads to lungs commonly. Lung cancer commonly occurs in older people, above 60.
Now after going through all this, you have clear cut knowledge about grades and stages of cancer. You can even tell how normal cells turn cancerous and which organs could be the next target after lung cancer if metastasis is occurring.
Hope you have liked it. Leave a comment and let me know your feedback. Later.