Rhabdomyosarcoma exhibitiig a mixture of alveolar and embryonal patterns
Diagnostic Criteria
Tumors showing mixed histologic features of embryonal and alveolar subtypes
These histologically distinct morphologies may be intermixed or distinct from each other
There is no percentage cutoff that facilitates classification of one tumor subtype over another
The presence of both alveolar and embryonal morphologic features is all that is required for the designation of mixed alveolar/embryonal rhabdomyosarcoma.
Anaplasia should be evaluated and reported as described for embryonal and alveolar subtyes
Expression of myogenin and PAX-FOXO1 fusion transcripts is variable
They may be concordant or discordant with histologic pattern, diffuse, focal or negative
Behavior and incidence unknown
Common sites of involvement
Extremities
Trunk
Population: most <10 years of age, however all ages have been reported
