Classification of cancer can be based on several criteria including the tissue of origin, the type of cell involved, and the degree of malignancy.
Here is a detailed classification:
1. Based on Tissue of Origin
A. Carcinomas:
These are cancers that arise from epithelial cells, which line the inside and outside surfaces of the body.
Carcinomas are the most common type of cancer and include:
I. Adenocarcinoma: Originates in glandular epithelial cells (e.g., breast, prostate, colon).
II. Squamous Cell Carcinoma: Arises from squamous epithelial cells (e.g., skin, esophagus, lungs).
III. Transitional Cell Carcinoma: Occurs in transitional epithelium (e.g., bladder).
B. Sarcomas:
Cancers that arise from connective tissues such as bone, cartilage, fat, muscle, and blood vessels.
Examples include:
I. Osteosarcoma: Cancer of the bone.
II. Chondrosarcoma: Cancer of cartilage.
III. Liposarcoma: Cancer of fat tissues.
C. Leukemias:
Cancers of the blood or bone marrow characterized by an abnormal increase in white blood cells.
Leukemias are classified based on the type of white blood cell affected and the rate of progression (acute or chronic).
D. Lymphomas:
Cancers that originate in the lymphatic system.
They are divided into two main types:
I. Hodgkin Lymphoma: Characterized by the presence of Reed-Sternberg cells.
II. Non-Hodgkin Lymphoma: A diverse group of lymphomas without Reed-Sternberg cells.
E. Central Nervous System Cancers:
These include cancers that arise in the brain or spinal cord. Examples are:
I. Gliomas: Originating from glial cells.
II. Meningiomas: Arising from the meninges.
2. Based on Cell Type
A. Germ Cell Tumors:
These originate from reproductive cells and are most commonly found in the testicles or ovaries.
B. Blastomas:
Cancers derived from immature "precursor" cells or embryonic tissue. Examples include retinoblastoma and neuroblastoma.
3. Based on Degree of Malignancy
A. Benign Tumors:
Non-cancerous growths that do not spread to other parts of the body. Examples include fibromas and lipomas.
B. Malignant Tumors:
Cancerous growths that invade surrounding tissues and can metastasize. These are the tumors typically referred to as "cancer."