From the archives of the AFIP. Genitourinary rhabdomyosarcoma in children: radiologic-pathologic correlation.

Rhabdomyosarcoma is the most common tumor of the lower genitourinary tract in children in the first 2 decades of life. Most cases of genitourinary rhabdomyosarcoma are of the embryonal histologic subtype and include tumors of the bladder, prostate, testes and paratesticular sites, penis, perineum, vagina, and uterus. The natural history, pattern of metastatic spread, treatment, and prognosis of childhood rhabdomyosarcoma vary with the anatomic site of the lesion. In children with rhabdomyosarcoma of the bladder or prostate, presenting signs and symptoms include urinary or fecal retention, dysuria, urinary tract infection, and hematuria. Paratesticular rhabdomyosarcoma produces painless scrotal swelling, which may be ignored until the tumor has reached a large size. Vaginal tumors may manifest as a prolapsing mass in the introitus. Radiologic studies of children with genitourinary rhabdomyosarcoma reflect the nonspecific gross features of the tumor, which may be ill defined with infiltrative margins or well circumscribed by a pseudocapsule of compressed tissue. The botryoid variant of embryonal rhabdomyosarcoma results when submucosal tumor produces a polypoid mass resembling a cluster of grapes within a hollow structure. Botryoid morphology is characteristic, but not specific, for rhabdomyosarcoma within the vagina or urinary bladder, since yolk sac tumor and "tumoral" cystitis may have a similar appearance. Invasion of adjacent structures by the primary tumor may make the precise anatomic origin of genitourinary rhabdomyosarcoma difficult to determine on cross-sectional images. Recent refinements in multidisciplinary therapeutic regimens combining chemotherapy, radiation therapy, and surgery have dramatically improved outcome for children with genitourinary rhabdomyosarcoma. Diagnostic imaging plays an important role in monitoring response to therapy.