Surgical Pathology Criteria

Inverted Papilloma

Differential Diagnosis

Inverted Papilloma Florid von Brunn Nests, Cystitis Cystica/Glandularis
Regular pattern of anastomosing cords and trabeculae Round nests, may show fusion
Peripheral palisading and central streaming Lacks biphasic palisading/streaming pattern
Criteria above apply to both solid and cystic processes
An older description of inverted papilloma composed of cystic nests (Kunze) may not be separable from florid von Brunn nests

Nested Variant Urothelial Carcinoma Inverted Papilloma
Overall invasive pattern, not circumscribed Circumscribed (if sample permits assessment)
May involve muscularis propria Does not involve muscularis propria
Varying sizes and shapes of nests Uniform trabeculae and cords
Disorder of cells in nests Orderly peripheral palisading and central streaming

Urothelial Carcinoma with Inverted Growth Pattern Inverted Papilloma
Usually has a surface papillary component Surface everted papillary component absent or minimal
Cytologic features and disorder of carcinoma, appropriate to grade Bland, uniform, orderly cells
Mitotic figures present, appropriate to grade No mitotic figures
These may represent a spectrum, with an intermediate PUNLUMP with inverted pattern

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