Cancer is not considered a single disease but several. The classification and types of cancer are based on the site of origin of the disease and its histological characteristics (composition, structure and characteristics) or tissue.
Depending on the site of origin
The primary site of origin gives the classification and types of cancer; they are considered to be of a specific kind, such as lung, brain, oral, liver, and kidney cancer, among others.
Depending on the type of fabric
Based on the type of tissue, six main categories of cancer types are classified and identified:
It is the most common type of cancer and originates in epithelial cells that cover the outside of the body (skin) and internal surfaces (mucosa).
When the carcinoma affects the surface of the organs that have a secretory function in the body, it is called adenocarcinoma (cancer of the breast, lung, colon, pancreas, prostate, etc.)
When the tumour affects the rest of the tissues that line hollow organs and the skin, it is called squamous cell carcinoma or squamous cell carcinoma (cancer of the skin, cervix, bladder, head, neck, vagina, etc.)
This type of cancer is prevalent in the young population. I am from bones (osteosarcoma) and soft tissues (such as muscle, cartilage, adipose or fatty tissue, blood vessels, lymphatic vessels) and fibrous tissues (tendons and ligaments).
This type of cancer starts in the marrow’s plasma cells (a type of white blood cell).
Plasma cells produce antibodies to respond to infections and diseases, so when the DNA of the cells is altered, they accumulate in the bone marrow, forming tumours in many bones.
It is considered a type of blood cancer because the abnormal plasma cells cause the blood to thicken and prevent the bone marrow from generating more healthy blood cells.
This type of cancer does not form solid tumours; they all start in the tissues that form blood in the bone marrow. They are also known as “liquid cancer”.
When present, the marrow produces excess immature white blood cells, which cannot fulfil their function of protection against infections and diseases, which makes the person more likely to get sick, and the DNA of their healthy cells is altered.
There are several types of leukaemia:
Acute myelocytic leukaemia (AML): It is common in childhood and is a cancer of the myeloid and granulocytic white blood cells.
Chronic myelocytic leukaemia (CML): occurs in adulthood and is a cancer of the myeloid and granulocytic white blood cells.
Acute lymphocytic, lymphocytic or lymphoblastic leukaemia (ALL): is a malignant neoplasm of lymphoid and lymphocytic white blood cells. It is common during childhood and in young adults.
Chronic lymphocytic, lymphocytic, or lymphoblastic leukaemia (CLL): is common in adulthood and is a malignant neoplasm of lymphoid and lymphocytic white blood cells.
Polycythemia Vera or erythremia: is cancer that occurs in the different components of the blood, mainly in the red blood cells.
Cancer originates in the immune system’s cells, specifically in the lymphocytes: T cells or B cells. It belongs to the lymphatic system. Unlike leukaemias, these cancers are “solid” or extranodal lymphomas that affect the lymph nodes in specific organs and places in the body, such as the stomach, brain, intestines, etc.
There are two types of lymphomas: Non-Hodgkin’s lymphoma and Hodgkin’s lymphoma; in the latter, there is the presence of cells called Reed-Sternberg in the tissue, which differentiates it from Non-Hodgkin.
Regarding the recovery prognosis, Hodgkin’s lymphoma has a greater chance of cure. In Non-Hodgkin’s lymphoma, it will depend on the specificity of the disease.
Mixed type or rare
It is when there are two or more components of cancer, such as a mixed mesodermal tumour, carcinosarcoma, adenosquamous carcinoma, teratocarcinoma, and blastomas (affect embryonic tissue).
according to grade
The grade of cancer or tumour is determined from 1 to 4 according to the increase in abnormal cells compared to normal cells. For this, the existence of differentiated or undifferentiated cells in the tissues of and around the tumour is considered:
- Grade 1 (G1): well-differentiated cells with slight abnormality.
- Grade 2 (G2): moderately differentiated cells with a minor exception.
- Grade 3 (G3): poorly differentiated cells with many monsters.
- Grade 4 (G4): Cells are immature and primitive, and undifferentiated.
According to the stage or stage
Staging is how cancers are classified individually and are the process of finding out how much cancer is in the body and how much it has spread. Its definition provides essential information for the doctor to plan treatment and determine the prognosis of recovery of the person and the extent of the disease.
- There are several methods to perform a staging (TNM) or classification of the state of cancer:
- Depending on the tumour size (T), which is the most used method.
- Depending on the regional spread or lymph node involvement (N).
- Distant metastasis (M).
- Cancer’s stage is determined by the identified degree (1 to 4) and the location (TNM) in which the disease is found. It is so:
- T0 means there is no evidence of a tumour.
- T, from 1 to 4, means that the size and involvement of the tumour are increasing.
- This is when there is carcinoma in situ or limited to superficial cells.
- N0 means that there is no lymph node involvement.
- N, from 1 to 4 are the increasing degrees of involvement in the lymph nodes.
- Nx implies that it is impossible to evaluate the lymph nodes’ participation.
- M0, when there is no evidence of distant spread (metastasis).
- M1, when there is evidence of distant spread (metastasis).
- TNM staging of cancer indicates the following:
- Stage 0: The tumour is in situ or limited to superficial cells.
- Phase I: The tumour is limited to the tissue of origin.
- Stage II: The tumour is confined locally spread.
- Stage III: The tumour is locally and extensively regionally disseminated.
- Stage IV: Advanced cancer that is distantly spread and metastasised.
- Depending on location in the body
- Cancers can be classified according to where they are in the body, which, in general, are:
- musculoskeletal system
- bone cancer
- Osteosarcoma and malignant fibrous histiocytoma of bone
- Ewing sarcoma
- Childhood rhabdomyosarcoma
- soft tissue sarcoma
- respiratory system and thorax
- Childhood pleuropulmonary blastoma
- Non-small cell lung cancer
- small cell lung cancer
- malignant mesothelioma
- Thymoma and thymic carcinoma
- Childhood tracheobronchial tumours
- Head and neck
- Mouth cancer
- Throat cancer
- salivary gland cancer
- hypopharyngeal cancer
- Childhood extracranial germ cell tumour
- Cancer of the lip and oral cavity
- laryngeal cancer
- nasopharyngeal cancer
- oropharyngeal cancer
- parathyroid cancer
- Paranasal sinus and nasal cavity cancer
- Thyroid cancer
- Metastatic squamous cell carcinoma of the neck with primary occult tumour