Rhabdomyosarcoma presents special diagnostic problems when it involves the uterine cervix in young children because
tumor cells may lack marked atypia and may blend with the normal, immature, condensed, cellular stroma, rendering diagnosis difficult. Myogenic makers are a valuable ancillary technique for establishing a diagnosis of
rhabdomyosarcoma. However,
desmin positivity has been reported in cervical stromal cells, which can confound diagnosis. To determine whether immunohistochemical markers of skeletal muscle differentiation are helpful in the diagnosis of uterine botryoid
rhabdomyosarcoma, we compared the immunohistochemical staining pattern of cervical
rhabdomyosarcoma from 3 patients with that of normal uteri from age-matched autopsy controls by using
antibodies for
desmin, smooth muscle actin, muscle-specific actin, myoD1,
myogenin, and WT-1. All
tumors demonstrated at least focal immunopositivity for
desmin, muscle-specific actin, smooth muscle actin, myoD1, and WT-1, and 1
tumor was also positive for
myogenin. Autopsy controls showed only scattered subepithelial stromal immunoreactivity for
desmin, muscle-specific actin, smooth muscle actin, and WT-1 and showed cytoplasmic, but not nuclear, immunopositivity for myoD1 and
myogenin. Myometrium was diffusely positive for
desmin and muscle-specific actin. We conclude that
desmin, muscle-specific actin, smooth muscle actin, and WT1 are not specific for discriminating
embryonal rhabdomyosarcoma from normal subepithelial cells in the female genital tract of children, although the number of immunopositive cells is consistently larger in
rhabdomyosarcoma. Nuclear staining for myoD1 and
myogenin appears not to occur in normal tissue, but it may be absent or sparse in
embryonal rhabdomyosarcoma. Our findings indicate that, in this anatomic site, the diagnosis of
rhabdomyosarcoma and in particular determination of
tumor margins remain very reliant on histomorphology.