Cancer is not a single disease; it’s a combination of over 200 diseases caused as a result of the rapid multiplication of abnormal cells, which spread to other tissues and organs in the body.
Cancer is one of the world’s leading causes of death. Due to the diversity of the disease, it’s difficult to diagnose.
However, you can better understand the type of cancer you have and how to manage it if you get to know more about all the cancer types.
Primary vs Metastatic
One factor that often sparks controversy when discussing types of cancer is when the condition metastasises (spreads) to other parts of the body.
When cancer spreads to another region, it is not named for the region which it spreads, but it’s named after the type of cancer cell or organ in which it began. This is known as primary cancer.
For instance, if lung cancer begins in the lung and later spread to the liver, it would not be called liver cancer. Instead, it would be referred to as primary lung cancer metastatic to the liver.
Rarely, doctors are unable to trace the origin of cancer, but only find evidence of where it has spread. This is referred to as cancer of unknown origin or unknown primary with metastasis to the region where it was found.
Types of Cancer
By body part or system
Sometimes, tumours are group by organ systems or organs in which they arise.
Head and Neck Cancers
This group of cancer can affect any part of the head and neck, even from the tongue to vocal cords.
Heavy smokers and drinkers are seen to have these ailments in the past, but in recent years, HPV(human papillomavirus) has become the primary cause. Two of such cancers are;
- Laryngeal cancer which affects the vocal cords.
- Oral Cancer. This condition may involve the throat, tongue, mouth, and nasal passageways. Close to 85% of head and neck cancers fall under this category.
Digestive System Cancer
This cancer can affect any region from the mouth to the anus. Most digestive tract cancers are adenocarcinomas, with squamous cell carcinomas occurring in the upper oesophagus and the most distant portion of the anus.
The types include;
- Pancreatic cancer: Though, not as common as others, but this cancer is the fourth leading cause of cancer deaths in both women and men. It is most times diagnosed in the later stage of the disease when surgery is no longer possible.
- Stomach cancer: This is a prevalent type of cancer worldwide, but it tends to be uncommon in the United States.
- Colorectal cancer: This cancer is most times known as colon cancer. It includes both the cancer of the upper colon and the rectum. It is the third most common cause of cancer-related deaths in both women and men.
- Anal cancer: This cancer is different from colon cancer both in causes and treatment. Human papillomavirus (HPV) related infections are now the major causes of anal cancers.
- Oesophagal cancer: The most common type of oesophagal cancer has changed in recent times. Squamous cell oesophagal cancer which is often related to smoking and drinking was one time the common form of the disease, but now it is the oesophagal adenocarcinoma which is often associated with long-standing acid reflux.
- Liver cancer: Primary cancers are less common compared to tumours metastatic to the liver. The risk factors for liver cancer include chronic infections with hepatitis B or C and alcohol abuse.
Skin cancers are classified into two primary groups: melanoma and non-melanoma. Melanoma skin cancers are responsible for most cancer deaths, while non-melanomas are more common. Examples of skin cancers are
- Squamous cell carcinoma of the skin
- Basal cell carcinoma.
Reproductive System Cancer
Reproductive organ cancer may occur in women and men. Ovarian cancer is the fifth leading cause of cancer-related deaths in women.
It is curable in the early stages, but it is most times diagnosed when it has already spread. The types include
- Cervical cancer
- Testicular cancer
- Endometrial cancer (also called uterine cancer)
- Fallopian tube cancer
- Ovarian cancer (including germ cell tumours)
The leading cause of cancer-related deaths in both women and men in the United States are the cancers of the lung and bronchial tubes. While smoking is a risk factor of these conditions, lung cancers can also occur in non-smokers
There has been an overall decrease in lung cancers, partly due to the reduction in smoking. However, it has been increasing in young adults, especially young women who do not even smoke. The types include;
- Mesothelioma: This cancer affects the lining surrounding the lungs, known as the pleural mesothelium.
- Small cell lung cancer: this cancer mostly occurs in active smokers and is responsible for about 15% of lung cancers.
- Non-small cell lung cancer: It accounts for around 85% of lung cancers. Subtypes include squamous cell carcinoma of the lungs, lung adenocarcinoma, and large cell lung cancer.
Bone and Soft Tissue Cancer
Primary bone and soft tissue cancers are not as common as cancers that metastasise to the bone.
However, both primary and metastatic bone cancers have common symptoms of pain or a pathologic fracture in the bone that is weakened by the presence of a tumour. The types include
- Ewing’s sarcoma: This is a bone cancer that primarily affects children
- Kaposi’s sarcoma: it is a soft tissue cancer that is seen with people with HIV/AIDS.
The endocrine system is made up of glands that produce hormones and, as such, symptoms such as under or overproduction of these hormones may occur.
Most endocrine cancers except for thyroid cancer are relatively rare. Multiple endocrine neoplasias which are a combination of different endocrine cancer may run in families.
The United States has experienced an increase in the incidence of thyroid cancer, more than any other cancer. Thankfully, there is a high survival rate for many of these cancers.
Urinary System Cancers
The genitourinary system involves the bladder, the kidneys, the tubes connecting the bladder and kidneys (known as the ureters), and the urethra, which is the passageway out from the bladder. Structures like the prostate gland are also part of the system. Types include;
- Bladder cancer: those who work with paint and dyes are at a high risk of this cancer. Half of bladder cancers are also caused by tobacco exposure.
- Prostate cancer: this is the second most common cause of cancer deaths in men. Now, it’s survival rate is up to five years.
- Kidney cancer: the most common type of kidney cancer include Wilm’s tumour in children, transitional cell carcinoma, and renal cell carcinoma, which accounts for about 90% of cases.
Blood-related cancers include both those involving solid tissues of the immune system and those involving blood cells.
The risk factor for blood-related cancer is a bit different from solid tumours because viruses (like Epstein-Barr virus) and environmental exposure play a significant role.
Blood-related cancers include
- chronic myelogenous leukaemia
- Hodgkin lymphoma
- non-Hodgkin lymphoma
- acute lymphocytic leukaemia
- chronic lymphocytic leukaemia
- chronic myelogenous leukaemia
Breast cancer is believed to affect mostly women; however, 1 out of 100 cases of these tumours occur in men. Ductal carcinoma is the most common type of breast cancer.
Most breast cancer cases may be detected early before they progress to invasive malignancy as most of them are carcinomas.
This is known as stage 0 breast cancer or carcinoma in situ. The invasive stages of the disease are stages 1 through 4. You may also hear;
- Lobular carcinoma in situ (LCIS) and ductal carcinoma in situ of the breast (DCIS): The earliest stage at which breast cancers can be detected is the stage 0 or carcinoma in situ. These cancers are considered non-invasive as they haven’t yet penetrated through the basement membrane. They are most times detected during a biopsy for any abnormality in screening mammogram.
- Inflammatory breast cancer: it does not really present a lump like other cancers. Instead, the early stage looks like a rash and redness on the breast.
- Invasive breast cancer (both ductal and lobular): breast cancer is said to be invasive when it penetrates through the basement membrane.
- Male breast cancer: a genetic component is involved when breast cancer occurs in men.
By cell type or tissues
A lot of cancers get their name from the type of cell in which they began. For instance, you may have been diagnosed with breast cancer, but breast cancer can differ significantly based on the kind of breast cell in which these tumours began.
Based on cell type, cancers are grouped into six major types. They include;
Also known as multiple myeloma, they affect the cells in the immune system that are responsible for the production of antibodies called the plasma cells.
These are cancers that primary to the cells of the immune system. They may start developing lymph nodes or from extranodal sites such as testicles, spleen or stomach. They are further grouped into
- The Hodgkin lymphoma
- Non-Hodgkin lymphoma.
These are cancers of the bone and soft tissues of the body that are composed of cells called mesenchymal cells.
These include cancers of the bones, tendons, fatty tissues, synovial tissues (joint tissues), nerves, blood vessels, cartilage, muscles (both smooth and skeletal muscle), and ligaments. Examples of sarcomas include
- Glioma and astrocytoma (cells that make up the connective tissue in the brain)
- Leiomyosarcoma (cancers that affect smooth muscles)
- Mesothelioma (cancers of the mesothelium, the tissues that surround the abdominal and chest cavities)
- Fibrosarcoma (fibroid tissues cancers)
- Angiosarcoma (blood vessel cancers)
- Rhabdomyosarcoma (skeletal muscle cancers)
- Chondrosarcoma (fatty tissue cancers)
- Osteosarcoma (bone cancers)
Carcinomas account for 80% to 90% of cancer cases, making it the most common cell type of cancer.
These cancers occur in cells called epithelial cells which include the cells of the skin and those that cover organs and line body cavity.
Carcinomas may be further grouped into
- Squamous cell carcinomas: examples of squamous cells include those in the lower portion of the vagina and cervix, the upper portion of the oesophagus and airways, and the top layer of the skin
- Basal cell carcinomas: they are the deepest layer of skin cells and can’t be found anywhere else in the body.
- Adenocarcinomas: they arise in glandular cells that produce fluids such as breast milk.
- Transitional cell carcinoma: they are the “stretchy” epithelial cells that are present in part of the kidney and the bladder.
Carcinomas can also derive their names from the location at which they arise. For example, breasts carcinomas that arise in the breast lobes are referred to as lobular carcinomas, whereas those that arise in the milk duct are considered ductal carcinomas
Leukaemias are cancers that affect blood cells, and they begin in the bone marrow. Among blood-related cancers, leukaemias are often referred to as “liquid cancers” in contrast to lymphomas and myelomas.
They are often treated like metastasised solid cancers since they occur in cells that circulate in the bloodstream.
- Myelocytic Leukemia: they are cancers of immature or mature cells known as myelocytes.
- Lymphocytic Leukemia: they are cancers of white blood cells called lymphocytes.
Both myelocytic and lymphocytic leukaemias have Acute forms (they progress quickly) and chronic forms (they take longer to develop).
Mixed types (including blastomas)
Some cancers do possess characteristics of more than one tissue type. Cancer cells are different from normal cells in many ways, one of which is known as differentiation.
Some cancer can look very different from the cells in which they originate (these are referred to as undifferentiated on a pathology report), yet others may share exact semblance with them (these are referred to as well-differentiated tumours).
Plus, most cancers are heterogeneous. This implies that the cells in one region of a tumour may look completely different from another region of a tumour. For instance, a lung cancer may have some cells that resemble squamous cell carcinoma and others that appear to adenocarcinoma. This would be explained in a pathology report as having adenosquamous attributes.
Blastomas are tumours that are sometimes separated from the others as they arise in embryonic cells. These are cells that have not yet chosen a path to become mesenchymal cells or epithelial cells.
Other classification methods
In addition to the classification of cancers, tumours are classified by;
- Tumour stage: there are different ways of staging tumours, but many are given numbers from one to four. Number four is usually the most advanced stage of cancer.
- Tumour grade: the aggressiveness of a tumour is measured by its grade. Grade one tumour is not very aggressive because the cells may still look like the normal cells in which cancer began. Grade three tumour is more aggressive because the cells look very different from the normal cells in which cancer began.
- DNA/molecular profiles: as our knowledge of genetics improves, tumours are being classified in terms of genetic profile. Some lung cancers have ALK rearrangements, while others have EGFR mutations.
- Hereditary cancers vs non-hereditary cancers: some cancers considered hereditary. For instance, about 10% of breast cancers are recognised as such. There is much overlap, and most cancers are influenced by genetics.
There are lots of cancer types in addition to those listed here, and, as noted, they sometimes share significant characteristics. It is likely that over the next decade, cancers classification will improve significantly as a result of increased understanding of genetics.
It is essential to know that people react differently to cancer treatment even if they have the same type or subtype cancer.
Get to know more about the type of cancer you have and keep in mind that even if a tumour is incurable, it is almost always treatable, and both the survival rate and treatments for cancer have been improving in recent years.