NCIt definition : An endophytic benign papillary epithelial neoplasm that results from the invagination
and proliferation of epithelial cells in the underlying stroma. Representative examples
are the inverted urothelial papilloma that arises from the urinary tract and inverted
Schneiderian papilloma that arises from the nasal cavity or paranasal sinuses.;
Alternative definition : NCI-GLOSS: A type of tumor in which surface epithelial cells grow downward into the
underlying supportive tissue. It may occur in the nose and/or sinuses or in the urinary
tract (bladder, renal pelvis, ureter, urethra). When it occurs in the nose or sinuses,
it may cause symptoms similar to those caused by sinusitis, such as nasal congestion.
When it occurs in the urinary tract, it may cause blood in the urine.;