| Papillary tumors of the urinary tract were for many years classified
either as papillomas or papillary carcinomas but there now is a third category
- papillary urothelial neoplasm of low malignant potential [45].
These resemble papillomas except that there is an increased thickness of
the epithelium. There is little or no atypia of the cells. The basal cells
may show palisading and there is little or no alteration of cell polarity.
Mitoses are rare and usually will be basal in location. Umbrella cells are
usually present but may not be prominent. For brevity, we will refer to
these lesions in the text as PUNLMP. They do not progress to carcinoma in
the overwhelming majority of cases but, unlike papillomas, the patients
have an increased risk of developing new papillary tumors. Occasionally,
these new tumors are of higher nuclear grade and are capable of malignant
progression. When the pathologist makes a diagnosis of PUNLMP a comment
should be included in the report: "Patients with these tumors are at risk
of developing new bladder tumors, usually of similar histology. However,
occasionally the subsequent lesion is a carcinoma. Follow-up is warranted."
[4]
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