There are two kinds of muscle cells in the body: smooth muscle cells and skeletal muscle cells. Smooth muscles control involuntary activities; skeletal muscles control voluntary activities. Rhabdomyosarcoma (RMS) is a malignant tumor ("cancer") that arises from a normal skeletal muscle cell.
Rhabdomyosarcomas are soft tissue sarcomas (a tumor of connective tissue) which originate frequently in the striated muscles (form of fibers that are combined into parallel fibers) of the body like the cardiac and the skeletal. The cells from which they develop are called myoblasts. The tumor most commonly occurs in oral cavity, larynx, pharynx, gingiva (gums), greater omentum, tongue and myocardium. Although these tumors originate from skeletal muscle, and are commonly reported in large-breed dogs, they can also derive from organs that lack striated muscle, such as the urinary bladder, uterus, cervix and vagina of small breeds.
On the basis of their location, rhabdomyosarcomas have been classified into embryonal, botryoid, alveolar and pleomorphic. Although carcinomatosis (wide spread to distant organs) is uncommon , they may spread to organs like the spleen, lungs, liver, kidneys and the adrenal glands. Rhabdomyosarcomas are mostly found in young animals.
The symptoms that are associated with RMS can vary widely depending on where the tumor develops.