The PAX7-FOXO1 fusion is often amplified in tumors (about 70 percent of all PAX7-FOXO1 fusion positive tumors) and the PAX3-FOXO1 fusion is rarely amplified (only in 5 percent of all PAX3-FOXO1 fusion positive tumors). About 60 percent of all ARMS cases are positive for PAX3-FOXO1 fusion gene, 20 percent are positive for PAX7-FOXO1 fusion gene, and the remaining 20 percent are fusion negative ARMS cases. Both fusion genes are composed of either the PAX3 or PAX7 DNA binding domains and the FOXO1 transactivation domain. This fusion causes a dysregulation of transcription and acts as an oncogene promoting cancer formation. Pathology
ARMS cells are often small with little cytoplasm. The nuclei of the cells are round with normal, dull, chromatin structures. The ARMS 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 ARMS from other rhabdomyosarcoma tumors and immunostaining for AP2β and p-cadherin can distinguish fusion positive ARMS from fusion negative. Embryonic origin and epidemiology
ARMS usually occurs in the skeletal muscles and is postulated to be derived from precursor cells within the muscle tissue. During embryonic development ARMS occurs in the mesoderm which is the precursor for the skeletal muscle tissue.
Pud may refer to:

Pudding, a typically sweet food
Comic strip mascot for Dubble Bubble
A nickname of Albert Kent, a Canadian football coach and olympic rower
A nickname of Philip J. Kaplan, an American entrepreneur
Pud Galvin, a Hall of Fame Major League Baseball pitcher
Pood or pud, an old Russian unit of weight
slang shortened version of "pudendum"PUD can be an acronym for

Planned Unit Development
Public Utility District, a consumer co-op owned utility
Peptic Ulcer Disease