What is Sarcoma?
Sarcomas are malignant tumors of the mesenchymal tissue. Mesenchyme is a term used to refer to the connective tissue of the embryo. The origin of the mesenchyme is predominantly mesoderm, but in the head, and neck region it arises from ectoderm. The mesenchyme has scattered cells with no junctions and a lot of intercellular matrix in between with no basement membrane. Any malignant change in the cellular component of the mesenchyme is known as sarcoma. Conversely, the malignancies arising from the cellular component (mesenchymal cells) of blood are called leukemias and lymphomas. The naming of sarcomas is according to the cell of origin, and their composition. They are rare types of cancers, and account for 20% of pediatric cases of solid malignant tumors. Malignant bone tumors constitute 13% cases of all sarcoma cases, and osteogenic sarcoma is the most common type.
Types of sarcoma
Sarcomas are divided according to the type of cell present in the tumor mass, and according to the cell of origin. For example, if it arises from fibrocyte it is called fibrosarcoma. Likewise, chondroblastoma is due to malignancy of chondrocytes, and osteogenic sarcoma arises from osteocytes.
Other examples are adipocytes, which can cause liposarcoma, sarcomas in the blood vessels known as angiosarcoma or Kaposi sarcoma, or the lymphatic vessels (lymphangiosarcoma). As for the smooth muscle, sarcoma in this tissue is known as leiomyosarcoma, and in the skeletal muscles cells it is called rhabdomyosarcoma. Similarly, synovial sarcoma arises from the synovium, and dermatofibrosarcoma from fibrohistocytes.
Other mesenchymal cells originate malignant tumors and misleadingly have an “oma” at the end. Those misnomers include mesothelioma (malignant tumor of parietal or visceral pleura, pericardial membrane), lymphoma (malignancies of the lymph tissue), schwannoma from Schwan cells (peripheral nerve sheath tumor), and meningioma (malignant tumor of meninges).