Paratesticular Leiomyosarcoma : Smooth Muscle Actin
Paratesticular leiomyosarcomas, like other soft tissue leiomyosarcomas, show smooth muscle differentiation immunohistochemically. This consists of positivity for smooth muscle actin (shown here), muscle-specific actin, and desmin. Focal positivity for cytokeratin and S-100 protein is seen in a small percentage of cases. Some cases also show CD34 positivity which is an unusual feature.