Rhabdomyosarcoma tumours arise from a cell called a “rhabdomyoblast”, which is a primitive muscle cell. Instead of differentiating into striated muscle cells, the rhabdomyoblasts grow out of control. Since this type of muscle is located throughout the body, the tumours can appear at numerous locations. The four major sites in which Rhabdomyosarcoma is found are:
- Head and neck; around the eyes — 35-40%
- Genitourinary tract — 20%
- Extremities — 15-20%
- Trunk (chest and lungs) — 10-15%
Depending on the “histology” of the cells (how they look under a microscope), the tumours are classified as one of the following:
- Embryonal Rhabdomyosarcoma. Most common type, usually found in children under 15 and in the head and neck region and genitourinary tract
- Botryoid type. A variant of the embryonal type; the tumour arises as a grape-like lesion in mucosal-lined hollow organs such as the vagina and urinary bladder.
- Alveolar type. A more aggressive tumour, which usually involves the muscles of the extremities or trunk.
- Pleomorphic type. Usually seen in adults and arises in muscles of the extremities.