PMC5992800_01
(A) Tumor mass showing a tumefactive neoplastic growth in continuity with the mesothelial lining (H&E, 20X). The neoplastic cells formed (B) diffuse sheets, nests and trabeculae (H&E, 100X) with (C) focal areas of infiltration into the underlying adipose tissue (H&E, 100X). (D) The neoplastic cells showed vesicular nuclei with nuclear atypia and frequent mitoses (H&E, 200X).
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Microscopic examination of sections from these nodular areas demonstrated a dense, expansile and tumefactive proliferation (Figure 1A) of medium-sized to large atypical epithelioid cells arranged predominantly in solid sheets, with focal nests and trabeculae formation (Figure 1B). The neoplastic proliferation focally invaded the underlying adipose tissue (Figure 1C). The neoplastic cells had pale to eosinophilic cytoplasm and vesicular nuclei with prominent nucleoli (Figure 1D).
Immunohistochemically, the neoplastic cells were strongly reactive for (A) CK7 and (B) CK5/6. The neoplastic cells showed partial but strong expression of mesothelial markers, including (C) nuclear/cytoplasmic staining for calretinin, (D) nuclear expression of WT1, and (E) D2-40 positivity (Immunoperoxidase, 200X).
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Immunohistochemical studies revealed the neoplastic cells to be strongly immunoreactive for pankeratin AE1/AE3, CK7 (Figure 2A), CK5/6 (Figure 2B), and Cam5.2, with partial, strong expression of mesothelial markers, including nuclear-cytoplasmic staining for Calretinin (Figure 2C), nuclear expression of WT-1 (Figure 2D), and D2-40 positivity (Figure 2E).