Embryonal Rhabdomyosarcoma with Posttherapy Cytodifferentiation and Aggressive Clinical Course

Figure 3

Histologic images from the posttreatment incisional biopsy of the right orbital mass. H&E stains demonstrate a variably cellular proliferation of terminally differentiated rhabdomyoblasts with eccentric nuclei and dense eosinophilic cytoplasm ((a) 100x magnification), with relatively few scattered foci showing primitive rhabdomyoblasts in the background ((b) 400x magnification). Immunohistochemical stains demonstrate scattered myogenin expression ((c) 100x magnification), infrequent myoD1 expression ((d) 100x magnification), and a low Ki67 proliferation index ((e) 100x magnification), all of which are markedly decreased in comparison to expression patterns from the pretreatment biopsy (Figure 2).

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