Rhabdomyosarcoma subtyping by immunohistochemical assessment of myogenin: tissue array study and review of the literature.

Myogenin immunostaining has been described as a useful marker of the alveolar subtype of rhabdomyosarcoma and as a tool for distinguishing it from the more common embryonal subtype. To add to the growing body of literature describing this phenomenon we analysed myogenin immunohistochemical staining in 152 tumors using a rhabdomyosarcoma tissue array. Results were analysed blinded to histological type by two independent investigators. Samples were excluded if any samples failed to stain with desmin and/or myogenin. Mean percentage of myogenin positive cells was significantly greater for ARMS (n = 31; mean percentage positivity 59% (95% confidence intervals +/- 7%) than ERMS (n = 41, mean percentage positivity 16%, 95% confidence intervals +/- 4; P < 0.0001). This data is consistent with previously published studies identifying strong nuclear myogenin staining in a high proportion of cells as a marker of alveolar histology.