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Washington University Experience | NEOPLASMS (NON-GLIAL NON-NEURONAL) | Choroid plexus papilloma | 16B3 Choroid plexus papilloma, atypical (Case 16) H&E 4

16B3-5 The cells lining the papillae are cuboidal to columnar with focal evidence of crowding and patchy areas of oncocytic change. The tumor cells have round to oval nuclei with mild to moderate pleomorphism. Nonetheless, there is a small area where this papillary architecture becomes blurred to a more solid growth pattern. The tumor cells in this area display moderate to marked pleomorphism with many showing prominence of nucleoli. Whereas the majority of the tumor has only a rare mitosis, it is relatively easy to find mitoses in this area and the count reaches ~5/10 HPF. Areas of necrosis and dense cellularity are, however, not seen. (H&E)

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