A Rare Case of Histiocytic Sarcoma Secondary to Gastrointestinal Stromal Tumor in the Stomach: Transdifferentiation or Synchronicity?

Figure 3

The 9.5 cm mass lesion consists predominantly of fibrotic stroma (80% of the mass) (×10) (a) with two distinct nodules measuring 1.0 cm and 0.6 cm (×2) (b). The two nodules are located in the inner surface of prior GIST  cavity showing large atypical epithelioid cells with abundant eosinophilic cytoplasm and prominent nucleoli (×40) (c). The cells were positive for CD4 (d), CD45 (e), CD68 (f), and CD163 (g), while negative for CD34 (h) and CD117 (i).

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