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1:
Inverted Papilloma
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Comments: The surface urothelium is normal or perhaps slightly attenuated. The lamina propria is expanded by proliferating urothelial cells arranged in solid nests or anastomosing trabeculae.
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2:
Inverted Papilloma
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Comments: The urothelial nests are sharply demarcated and surrounded by delicate fibrovascular stroma.
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3:
Inverted Papilloma
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Comments: There is no cytologic atypia in this case. Rare cases may show mild cytologic atypia. Increased mitotic is usually not seen.
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4:
Inverted Papilloma
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Comments: In this example, the urothelial cells have more basaloid appearance. Some urothelial cell clusters have central cystic spaces which may create pseudoglandular appearance.
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5:
Inverted Papilloma
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Comments: Non-keratinizing squamous metaplasia is seen in this inverted papilloma. Intestinal metaplasia, spindle cell pattern, and neuroendocrine differentiation are some of the other features that may be seen occasionally.
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6:
Inverted Papilloma
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Comments: This panoramic low power view shows how inverted papillomas can often create an exophytic mass.
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