<unk>  cells are often small with little cytoplasm. The nuclei of the cells are round with normal, dull, chromatin structures. The<unk>  cells often clump together and have fibrovascular septae that interrupts the aggregates. The fibrovascular septae that disrupts the aggregates often give the tumor the physiology of the alveoli found in the lungs. In a few cases, there may not be any fibrovascular septae and this gives the tumor a more solid phenotype and no alveoli physiology. Immunostaining for myogenin and for MyoD can be used to determine<unk>  from other rhabdomyosarcoma tumors and immunostaining for AP2β and p-cadherin can distinguish fusion positive<unk>  from fusion negative. Embryonic origin and epidemiology<unk>  usually occurs in the skeletal muscles and is postulated to be derived from precursor cells within the muscle tissue. During embryonic development<unk>  occurs in the mesoderm which is the precursor for the skeletal muscle tissue.<unk>  accounts for roughly 20 to 30 percent of all rhabdomyosarcoma tumors and therefore accounts for roughly 1 percent of malignancies found in children and adolescents. There is an age determination on which PAX proteins fuse together with the FOXO1 transcription factor. PAX3-FOXO1 positive subset of<unk>  occurs mostly in older children and young adults, while PAX7-FOXO1 positive subset of<unk>  and fusion negative subsets occur most often in younger children. Clinical<unk>  usually occurs in the skeletal muscle tissue of the extremities, but it is still very common in the torso, head, and neck regions. The primary tumor often presents itself as a soft mass of tissue that is painless, but the tumor can be detected if it starts to put pressure on other structures in the primary site. A large fraction of patients who are diagnosed with<unk> , roughly 25-30 percent, will have metastases at the time of diagnosis. The standard sites for metastases to form are the bone marrow, the bones, and distal nodes. Typical treatment options for patients who have been diagnosed with<unk>  include standard surgery, radiation therapy, and intensive chemotherapy.
Alveolar rhabdomyosarcoma
Sclerosing rhabdomyosarcoma
Spindle cell rhabdomyosarcoma
Neurofibroma
Lipoblastoma
Enchondroma
Nesidioblastoma
Esthesioneuroblastoma