PMC5724926_01
Morphological features of yolk sac tumor (A). Tumor with reticular pattern adjacent the gastric foveolar epithelium (B). Tumor cells, with pale eosinophilic cytoplasm and vesicular nuclei, appear to be arranged into microcystic and papillary or pseudopapillary structures. The tumor cells show immunoreactivity for cytokeratin (C) and for AFP (D).
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F1
Majority of the tumor was occupied by a YST which showed the most common reticular pattern (Fig. 1A, Fig. 1B). In the yolk sac component, tumor cells showed immunoreactivity for cytokeratin (Fig. 1C) and AFP (Fig. 1D) but not for CEA, chromogranin A, cytokeratins 7 and 20, beta-HCG, CDX2, placental alkaline phosphatase, and CD30.
The adenocarcinomatous component of the tumor shows atypical tubular glands with luminal necrotic material (A). Focal AFP immunostaining in the adenocarcinoma component (B).
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F2
AFP was also observed in the adenocarcinoma foci (Fig. 2). Alternatively, CEA was strongly positive in the adenocarcinoma.