<unk>  <unk>  is a very rare type of<unk>  tissue sarcoma - a slow growing tumor of an unknown origin that arises mainly in children and young adults.<unk>  is highly angiogenic: it involves intensive growth of new blood vessels, that connect the tumor to the blood system and enable dissemination of tumor cells into the bloodstream. Tumor cells can then easily migrate into other<unk> s of the body - typically the lungs, and the brain.<unk>  is a sarcoma, and that indicates that this cancer initially arises in<unk>  tissues that connect, support, or surround other structures and organs of the body, rather than bones. Typically,<unk>  arises in muscles and deep<unk>  tissue of the thigh or the leg (lower extremities), but can also appear in the upper extremities: the hands, the neck, and the head. While<unk>  is a<unk>  tissue sarcoma, it can spread and grow inside the bones.
The term<unk>  comes from the microscopic pattern, visible during the analysis of slides of<unk>  under the microscope in histopathology. The tumor cells seem to be arranged in the same pattern as the cells of the small air sacks (alveoli) in the lungs. However, this is just a structural similarity.<unk>  was first described and characterized in 1952.
Alveolar soft part sarcoma
Malignant fibrous histiocytoma
Epithelioid sarcoma
Soft tissue sarcoma
Granulocytic sarcoma
Oncocytoma
Reticulum cell sarcoma
Mycetoma