PMC7450305_01
(a) A representative histologic section of the appendix. At scanning magnification, a gland-forming neoplasm composed of tightly-packed acini involves the appendix from the mucosa to the muscularis propria, H&E x20. (b) At higher magnification, the tumor demonstrates variably sized, but predominantly small, back-to-back acini composed of cells with clear to amphophilic cytoplasm and enlarged nuclei. Amphophilic secretion is present in some tumor lumina, H&E x100. (c) The tumor cells show strong and diffuse nuclear positivity for NKX3.1, confirming the diagnosis of metastatic prostatic adenocarcinoma, x100. (d) The tumor cells also show strong cytoplasmic immunopositivity for prostate-specific antigen, further confirming the diagnosis. The luminal epithelium of the appendix (bottom left of the image) is unstained, providing a negative control for the test, x100.
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fig1
Histopathologic examination showed malignant epithelial cells arranged in crowded tubules extending from the lamina propria to the muscularis propria (Figures 1(a) and 1(b)), with involvement of the resection margins. Positive immunolabeling of the neoplasm for NKX3.1 (Figure 1(c)) and PSA (Figure 1(d)) confirmed the diagnosis of metastatic prostatic adenocarcinoma.