Immuno-histochemical localization of myoglobin in human muscle tissue and embryonal and alveolar rhabdomyosarcoma.

An immuno-histochemical investigation of the presence and localization of myoglobin was performed on cardiac and skeletal muscle tissue and on 9 embryonal and 9 alveolar rhabdomyosarcomas, utilizing an immunoperoxidase technique. Cardiac muscle fibres were evenly stained whereas staining of skeletal muscle fibres varied, giving a mosaic-like pattern. Of the fixatives used (4 percent formaldehyde, 4 percent paraformaldehyde, formaldehyde-glutaraldehyde, and Bouin's fixative), 4 percent formaldehyde gave the most prominent staining; short fixation-time slightly increased the staining intensity. All the 9 embryonal and 9 alveolar rhabdomyosarcomas contained positively-stained tumour cells. The number of cells positively-stained and the intensity of the staining varied with differentiation: the most differentiated rhabdomyoblasts stained most intensely. However, also many poorly-differentiated tumour cells in highly cellular areas were positive. Myoglobin is considered a suitable marker of rhabdomyoblastic differentiation, thus the method used in this study may be valuable in the diagnosis.