Rhabdomyosarcoma : Incidence
Incidence of Rhabdomyosarcoma (RMS): The most commonly affected age groups are infants, children, adolescents, and young adults. It is the most common soft tissue sarcoma in children under 15 years of age. It makes up 4.5% of all childhood cancers. There is a bimodal distribution with respect to age. The first peak is seen between 2 and 6 years and consists mostly of embryonal, botryoid, and spindle cell subtypes. The second peak occurs between 10 and 18 years and consists mostly of alveolar RMS. RMS is uncommon after the age of 45 years and makes up 2% to 5% of all adult sarcomas. Adult RMS are usually embryonal and spindle cell subtypes. The spindle cell RMS in adults differ from those seen in children. There is some correlation between tumor location and age. Rhabdomyosarcomas of urinary bladder, prostate, vagina, and middle ear tend to occur at a younger age (median age 4 years). For paratesticular and lower extremities, the median age is 14 years. This low-magnification view of an embryonal rhabdomyosarcoma shows darker cellular areas alternating with lighter myxoid areas.