Embryonal Rhabdomyosarcoma with Posttherapy Cytodifferentiation and Aggressive Clinical Course

Figure 2

Histologic images from pretreatment incisional biopsy of the right orbital mass. H&E stains demonstrate a hypercellular proliferation of rhabdomyoblasts, showing a spectrum from primitive to differentiating forms, the latter of which feature elongated eosinophilic cytoplasm (strap cells) ((a) 100x magnification; (b) 400x magnification). Immunohistochemical stains demonstrate frequent myogenin staining of moderate intensity ((d) 100x magnification), strong myoD1 expression ((e) 100x magnification), and a high Ki67 proliferation index ((e) 40x magnification) in the rhabdomyoblasts.

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