Papillary Urothelial Tumors with Inverted (Endophytic)
Growth Pattern
(e.g., papillary urothelial neoplasm of low
malignant potential and grade I papillary carcinoma with features of
inverted papilloma.)
Papillary neoplasms consist, by definition, of exophytic fronds projecting
into the lumen of the bladder, but many of these also show proliferation
down into the stroma--endophytic growth [7].
The result is a tumor which may bear a striking resemblance to the inverted
papilloma. Unlike the latter, the proliferation does not have the uniformly
narrow, anastomosing cords but, rather, large bulbous or plate-like masses
of epithelium. Most of these lesions will be classified as grade I papillary
carcinoma or as papillary urothelial neoplasm of low malignant potential,
and they will behave as such rather than as inverted papillomas. Most of
them will have at least a few exophytic papillations, but occasionally the
initial tumor or one of the subsequent "recurrences" will be entirely inverted
(Figures 1-3). |
