The present study is an immunohistochemical analysis utilizing a series of mono- and polyclonal
antibodies to
myoglobin,
desmin and
vimentin in smooth and striated control muscle tissues, 7 alveolar and 7
embryonal rhabdomyosarcomas and 1 adult and 1 fetal
rhabdomyoma with ultrastructurally proven rhabdomyoblastic differentiation in all the
tumors.
Formaldehyde-fixed and
paraffin-embedded tissue was used for the immunohistochemical analysis of all the
tumors, while
ethanol fixation was also used for the analysis of the control tissues. The staining for
myoglobin with the poly- and
monoclonal antibody used was positive in both
formaldehyde- and
ethanol-fixed skeletal and cardiac control muscle.
Trypsin treatment abolished the positive staining when the
monoclonal antibody was used. Both the striated and smooth control muscle tissues were positively stained by the antidesmin
antibodies. The influence of the
fixative that was used and the
trypsin treatment depended on the antibody used and the type and origin of the muscle tissue. All the
tumors were positively stained with the polyclonal antimyoglobin and 8/14
rhabdomyosarcomas and the 2
rhabdomyomas were positively stained with the monoclonal antimyoglobin. All the
tumors were positively stained with the polyclonal and 3 of the 5 monoclonal antidesmin
antibodies used. Well-differentiated
tumor cells were usually positively stained for both
myoglobin and
desmin. There were small, poorly differentiated
tumor cells in the
rhabdomyosarcomas and the fetal
rhabdomyoma which were positively stained for
desmin, whereas very few or no such cells were positively stained for
myoglobin. A varying number of mostly small, poorly differentiated
tumor cells were positively stained for
vimentin in 12 of 14
rhabdomyosarcomas and in the fetal
rhabdomyoma. The study showed that one of the monoclonal antidesmin
antibodies produced the most consistent result with a positive staining in all cases. The monoclonal antimyoglobin antibody, which is a specific marker of rhabdomyoblastic differentiation, is also considered to be of value, although it did not produce positivity in all cases. It remains to be shown whether
desmin can help in the diagnosis of poorly or undifferentiated
rhabdomyosarcomas without light- or electron-microscopic evidence of rhabdomyoblastic differentiation.