Evaluation of desmin as a diagnostic and prognostic marker of childhood rhabdomyosarcomas and embryonal sarcomas.

The diagnostic and prognostic relevance of desmin expression in 80 rhabdomyosarcomas (RMS) and 5 embryonal sarcomas (ES) was examined using a peroxidase anti-peroxidase staining procedure. Fifty-nine RMS but only one ES stained for desmin (P less than 0.05). The maximum percentage of desmin containing cells was 49 in RMS compared with only 1% in ES. Desmin positivity correlated inversely with survival (P less than 0.02) in that RMS with high proportions of desmin positive cells were associated with poorer prognoses than those containing fewer desmin positive cells. If the degree of expression of desmin is related to myogenic differentiation, then our results indicate that poorly differentiated RMS tend to have a better prognosis than the well differentiated tumours. One possible explanation is that the poorly differentiated RMS respond better to chemotherapy than to well differentiated RMS. A multivariant analysis incorporating desmin staining, treatment, histology, age and gender revealed that the two most significant independent prognostic factors were treatment and histology.