Tumors may be classified in a variety of ways depending upon:
a. Primary site of origin
b. Tissue types
Tumors may be classified into different types depending on the primary site of origin. These include:
10. Tumors of breast
11. Pituitary tumors
12. Thyroid tumors
13. Tumors of kidney
Classification depending upon tissue types
Depending upon the tissue types, we may classify cancers into six main categories:
6. Mixed types
The cancer which arises from the epithelial layer, either present on the external parts of the body or the internal lining of organs is known as carcinoma. Carcinomas form the most common variety of tumors. These are commonly found in the breast, lungs, bladder, colon and prostate.
Carcinomas are further divided into two varieties:
Carcinomas that develop in an organ or gland constitute adenocarcinomas.
b. Squamous cell carcinomas
Carcinomas that originate from squamous epithelium constitute squamous cell carcinomas.
The cancers which originate from the supporting tissues of the body i.e. connective tissue, muscles, bones, carilage and fat are known as sarcomas. Common examples of sarcomas include:
- Osteosarcoma in bones
- Chondrosarcoma of cartilage
- Leiomyosarcoma of smooth muscles
- Rhabdomyosarcoma of skeletal muscles
- Fibrosarcoma of fibrous tissue
- Angiosarcoma of blood vessels
- Liposarcoma of adipose tissue
- Astrocytoma of connective tissue in brain
The cancers which originate from plasma cells present in bone marrow constitute myelomas. These may be regarded as a type of blood cancers.
The cancers which affect bone marrow leading to excessive production of immature white blood cells constitute leukemias. These are also a variety of blood cancers. As white blood cells are involved in providing immunity, thus a person suffering from leukemias becomes prone to infections.
Leukemias may be classified into:
a. Acute lymphocytic, or lymphoblastic leukemia (ALL)
b. Chronic lymphocytic, or lymphoblastic leukemia (CLL)
c. Acute myelocytic leukemia (AML)
d. Chronic myelocytic leukemia (CML)
e. Polycythemia vera
The cancers which originate in lymphatic system constitute lymphomas. These may affect lymph nodes as well.
Lymphomas may be divided into:
a. Hodgkin’s lymphomas
b. Non Hodgkin’s lymphomas
6. Mixed types
As the name indicates, these have more than one varieties. Common examples are:
Classification depending upon Grade
Cancers may be classified into different varieties depending upon the grade. These include:
G1 -Well differentiated
G2 -Moderately differentiated
G3 -Poorly differentiated
For more information see grading of tumors.
Classification depending upon Stage
Cancers may also be classified depending upon the stage. the TMN classification is used.
T -tumor size
N -nodal spread
For more information see staging of tumors.