Cancers are classified according to the tissue and cell type from which they originate. Therefore, each cell type develops into a different type of cancer. Each type of cancer looks different under the microscope, behaves differently, causes different symptoms, and needs different treatment.
As cancers progress the cells may lose the features that identify them as originating from a particular organ. Well-differentiated cancers are those that retain the morphological features of their cellular organ. Poorly differentiated or undifferentiated cancers have lost most of their distinguishing morphological features.
Cancers can be broadly categorized according to the main type of cell from which they originate and further subdivided according to their specific cell type. These broad categories are:[i]
- Carcinoma
- Sarcoma
- Hematologic cancer
- Central nervous system cancer
Cancers are also categorized as solid tumors or those that do not form a solid mass. Solid tumors arise in solid organs and include cancers of the lung, colon, pancreas, breast, and prostate. Blood cancers that arise and proliferate in the bone marrow do not form solid tumors but crowd out normal blood cells and circulate in the blood. Sometimes referred to as “liquid” or hematologic cancers, these are the leukemias, lymphomas, and myeloma.[ii]
Carcinoma
Carcinoma is a general term that refers to any cancer originating in skin or tissues that line or cover internal organs. Types of carcinomas include adenocarcinoma and squamous cell carcinoma.20
Sarcoma
Sarcomas are cancers that arise from connective tissue, including bone, cartilage, muscle, and stromal tissue.20 Examples of sarcomas are liposarcoma, rhabdomyoma, and Kaposi’s sarcoma.[iii]
Hematologic Cancers
Hematologic cancers arise from blood cells in the bone marrow. Leukemias and myeloma are characterized by uncontrolled proliferation of white blood cells that circulate in the blood and crowd out normal blood cells. Lymphomas are characterized by uncontrolled proliferation of white blood cells that form tumors in lymphoid and other tissues.20
Central Nervous System (CNS) Cancers
CNS cancers are those that arise in the brain or spinal cord.20 There are several different types of CNS cells, and each produces a different type of CNS cancer. These include astrocytoma, glioblastomas, oligodendrogliomas, ependymomas, medulloblastomas, and meningiomas.[iv]
Summary
- Cancers are classified according to the tissue and cell type from which they originate; each cell type develops into a different type of cancer.
- The main types of cancers are: carcinoma, sarcoma, hematologic cancer, and CNS cancer.
- Carcinoma is a general term that refers to any cancer originating in skin or tissues that line or cover internal organs.
- Sarcomas are cancers that arise from connective tissue, including bone, cartilage, muscle, and stromal tissue.
- Hematologic cancers arise from blood cells in the bone marrow and include leukemias, myeloma, and lymphomas.
- CNS cancers are those that arise in tissues of the brain and spinal cord.
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[i] National Cancer Institute. What is cancer? 2013:1-3.
[ii] Stem Cell Network. Cancers: solid tumors. http://www.stemcellnetwork.ca/index.php?page=cancers-solid-tumor. Accessed August 15, 2013.
[iii] American Cancer Society. Sarcoma-adult soft-tissue cancer. 2012; 1-42.
[iv] American Cancer Society. Brain and spinal cord tumors in adults. 2012; 1-55.