Types of cancer: definition, risks and how they are classified


Cancer, unfortunately, is a very frequently talked about disease today. According to estimates by the Spanish Society of Medical Oncology (SEOM), in 2015, 220,000 new cases were diagnosed in the Spanish territory.

Likewise, the same institution affirms that the future is alarming, since taking into account the forecasts of the United Nations (UN), it is estimated that in 2020 246,713 new cases of cancer will be diagnosed in Spain, 97,715 in women and 148,998 in men.

What is cancer?

Our bodies are made up of millions upon trillions of cells, which are so small that they can only be seen through a microscope. These cells are grouped to form the tissues and organs of our body, and among them we find a great diversification as they perform different functions. With this supplementation they cover the vital needs of an organism, such as the maintenance of the body structure, nutrition and respiration.

Cancer occurs when normal cells become cancerous, that is, they multiply uncontrollably and invade adjacent organs or tissues.

Types of cancer

Cancers can start anywhere in the body and are named and classified based on different characteristics. But what types of cancer are there? We will explain them to you below.

A) Types according to their prognosis (benign or malignant)

Although many people think that the word cancer and the term tumor are the same, they are not. Tumors can be benign or malignant. If the tumor is benign, the cells multiply uncontrollably but without spreading to other parts of the body. The benign tumor does not usually represent a risk to the patient’s life, but if it is not treated in time, it could become a malignant or cancerous tumor.

The malignant tumor or cancer occurs when uncontrolled cells spread to other areas of the body, which is called metastasis.

B) Types of cancer according to origin

Depending on their origin, cancers are given specific names. For example:

Breast or chest cancer
Lung cancer
Colon cancer
Prostate cancer
Kidney cancer

C) Depending on the type of fabric

The International Classification of Diseases for Oncology (ICD-O) has been in use for nearly 25 years and is considered a prognostic and diagnostic tool for coding tumors and cancers.

1. Carcinoma
This is the most common type of cancer, and it originates in the epithelial layer of cells. These cells are the ones that line the entire surface of the body as well as the internal structures and cavities. Carcinomas can occur in different parts of the body, such as the lung, breast, prostate, and colon.

There are different types of carcinomas:

Embryonal carcinoma: has its origin in the cells of the testicles and ovaries.
Carcinoma in situ: it is not yet in the initial phase nor has it spread. They are removed with surgery.
Carcinoma of unknown origin: its place of origin is unknown.
Invasive carcinoma: is one that has invaded other areas. It receives the name of carcinomatosis.

2. Sarcoma
Sarcoma is a malignant tumor of connective tissues, including: muscle, bone, cartilage, and fat.

Depending on the origin, there are different subtypes of sarcoma:

Osteosarcoma: bone sarcoma
Chondrosarcoma: sarcoma of cartilage
Leiomyosarcoma – affects smooth muscles
Rhabdomyosarcoma: impact on skeletal muscles
Mesothelioma: affects the tissue that lines the lungs and chest cavity (pleura), the abdomen (peritoneum), or the sac that contains the heart (pericardium)
Fibrosarcoma: affects fibrous tissue
Angiosarcoma. has its effect on the blood vessels
Liposarcoma: sarcoma that affects adipose or fatty tissue
Glioma: originates in the brain or spinal cord. arises from glial cells
Myxosarcoma: Occurs in primitive embryonic connective tissue)


3. Myeloma
Myeloma or multiple myeloma is a cancerous tumor that originates in the plasma cells of the bone marrow. Normal plasma cells are an important component of the immune system, as the immune system is made up of several types of cells that work together to fight disease and infection. For example, lymphocytes.

4. Leukemia
Leukemia is a type of blood cancer that affects around 5,000 people in Spain each year. Leukemia occurs when different cells become cancerous affecting the bone marrow. Although it might seem that leukemia and myeloma (explained in the previous point) are the same, in reality they are not.

You may even have more questions when you hear the name of a type of leukemia called myeloid leukemia. Well, multiple myeloma and myeloid leukemia involve different types of cells. Although the cells affected in leukemia are also generated in the bone marrow, these are not plasma cells.

Leukemias can be classified based on different criteria:

Based on its history: “de novo”, as there is no previous process; and “secondary”, when there is a previous process (for example, blood disease) that leads to leukemia.

Based on transformation and speed: “acute leukemia”, if the development is rapid; and “chronic leukemia”, that is, slowly progressing.

Depending on their place of origin: “lymphoblastic”, affect lymphocytes; and “myeloblastic” (myeloid or myelocytic), which affect the precursor cells of the myeloid series or red series, such as red blood cells and platelets.


5. Lymphoma
If there could be doubts between leukemia and myeloma, the terms lymphoma and leukemia can also be confusing. But leukemia is often called liquid cancer because it affects the blood, while lymphomas are known as solid cancers because they originate in the lymph nodes.

Lymphomas are classified in two ways: Hodgkin’s lymphoma and Non-Hodgkin’s lymphomas. These types of lymphomas are different in behavior, spread, and treatment.

6. Mixed types
These cancerous tumors are characterized by the presence of two or more carcinogenic components. They are rare and can be caused by a poor prognosis. A mixed-type cancer is, for example, carcinosarcoma, a mixture of carcinoma and sarcoma. That is, it is a cancer of the epithelial tissue and at the same time connective, bone, cartilaginous or fatty. However, there are other rare “mixed type cancers”, such as mixed mesodermal tumor, adenosquamous carcinoma or teratocarcinoma.

D) Types according to grade
Depending on the degree of evolution, cancer can be classified into 4 levels. The greater the differentiation or abnormality and the greater or lesser speed of evolution, the greater the number of degrees.

The grades of this classification, proposed by the World Health Organization (WHO), “should be considered as grades of malignancy and not as stages of malignancy, regardless of whether certain grade III or IV tumors are the result of a malignant transformation of a pre-existing tumor”, explains this institution. Therefore, according to the grade, the WHO classifies tumors in:

1. Low-grade or slowly evolving
According to whether or not they have a circumscribed character

Grade I: slow evolution and circumscribed limits. Better prognosis than grade II
Grade II: slowly evolving but with diffuse limits and imprecise extension. Lower prognosis than grade I
2. High grade and fast growing
According to the evolution of the prognosis and the degree of abnormality.


Grade III: Anaplastic foci (poorly differentiated or undifferentiated cells) give a grade III label to an existing tumor, that is, it was low grade.
Grade IV: it is the most serious and the undifferentiated cells occupy the entire large part or the entire tumor.

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