Cancer, medically termed as "Malignant Neoplasia", can be defined as an abnormal mass of tissue. Its growth is inept and exceeds the growth of the normal tissue from where it arises. The mass continues its development even after the stimuli ceases that instigated the growth. Sometimes the genetic changes strike unwarranted and unregulated proliferation and after certain time, the changes become independent.
Cancer can be of several types. Here, it has to be kept in mind that all the tumors are not malignant. Some of them are benign and do not cause much harm unlike the cancer. Malignant tumors occurring from mesenchymal tissues (like connective tissues â€“ bone, cartilage, blood, lymphatic system) are generally termed as "Sarcomas". They are fleshy (Greek "sar" = flesh) in their texture. The cancers arising from the muscles present in our body are "Fibrosarcoma" (contains much fibrous tissues), "Liposarcoma" (arising from fat producing glands), "Leiomyosarcoma" (from the smooth muscles) and "Rhabdomyosarcoma" (cancers of the striated muscles).
Cancers can arise from the epithelial cells (the lining cells of every organ) also. They are nomenclature as "Carcinomas". If the tumor contains predominantly glandular cells, it is further termed as "Adenocarcinoma". "Squamous cell carcinoma" specifies the tumors where the epithelial squamous cells are the main component. Where the specific type of cell cannot be distinguished, it is termed as "undifferentiated or poorly differentiated malignant tumors".
Sometimes, multiple cell lines proliferate together and produce a tumor. It is called "Mixed tumor" (as in case of Mixed salivary gland tumor). This special type of tumor contains epithelial components spread inside a mixoid base. Sometimes, cartilage and bones are also present in this type of tumors. Practically, most of the cancers show mixed type of origin. "Teratoma", a special type of malignant tumors, contains all three layers of germinal cells. They arise from a particular cell call "Totipotent cell" which is predominantly found in gonads (testes and ovary). These special cells give rise to all kind of tissues. Practically, a teratoma may contain tooth, bone, skin, fat and muscle.
Specific names are given to the cancers arising from definite sources. Cancers of the testes are called "Seminoma", and that arising from the melanocytes present in the skin is called "Melanoma". Cancer of the liver cells is called "Hepatoma" and that from the kidneys are called "Nephroma".
Cancer of different organs is classified according to their origin. Squamous cell carcinoma and Adenocarcinoma", both can occur in the lungs. In the brain, it can be "Meningioma" (cancer of the meninges), "Glioma" and others. Cancers of the bone can be "Osteosarcoma", "Osteoblastoma", "Giant cell tumors" and others.