Rhabdomyosarcoma (RMS) is a type of sarcoma that is made up of cells that typically develop into skeletal muscles, or voluntary muscles, that we use to physically move our body.

Before birth, rhabdomyoblasts (cells that will form into skeletal muscles) begin to form, and it’s these cells that develop into RMS. This is cancer that predominantly affects children, but there are cases of adults with RMS.

Types of RMS

There are two main types of RMS, along with other rarer forms.

The first is embryonal rhabdomyosarcoma (ERMS), which typically affects children 5 years or younger, but it can occur at older ages as well. ERMS is most commonly found in the head and neck area, bladder, vagina, or in or around the prostate and testicles.

Two subtypes of ERMS, botryoid and spindle cell rhabdomyosarcomas, tend to have a better prognosis than the more common form of ERMS.

The second is alveolar rhabdomyosarcoma (ARMS), which affects adults and children equally. ARMS occurs mostly in the large muscles of the trunk, arms, and legs. ARMS progresses faster than ERMS, and often requires more severe treatment, but there are a few cases where the cancer cells will lack certain gene changes and easier treatment may be used.

A rare form exists called anaplastic rhabdomyosarcoma, which is rare and occurs in more adults than children. Because this is a RMS that occurs in adults, it is harder to treat as adults are more likely to have a fast-growing RMS and to have them in parts of the body that are difficult to treat or operate on.