| These are graded on a scale of I to III since rate of progression
differs with each of the three grades [61].
When the tumor histology varies from one microscopic field to another, the
highest grade encountered becomes the grade of the tumor. (It has not been
satisfactorily established if extremely small foci of high grade cells impact
on the prognosis.) In the WHO classification of bladder tumors, the following
characteristics are used to distinguish the three grades:
The epithelium of grade I urothelial carcinomas has an overall orderly
appearance but with easily recognizable variations of architectural and
cytologic features. In contrast to the papillary urothelial neoplasms of
low malignant potential, it is easy to recognize variations of nuclear
polarity, size, shape, and chromatin. Mitoses are infrequent, but may
occur at any level of the epithelium, usually the basal third. Fronds
should be evaluated where sectioned lengthwise through the core or when
sectioned at right angles away from the base. Otherwise, there may be a
misleading impression of increased cellularity and mitoses, or loss of
polarity (Figure 1 and Figure 2).
Grade II tumors exhibit an intermediate degree of abnormality. They are
distinguished from grade I by a predominately disordered architectural
pattern but with retention of some elements of organization, e.g.,
polarity and nuclear uniformity (Figure 3 and Figure 4). These elements
are not seen in grade III.
Grade III tumors present an impression of complete disorder or chaos
with absence of polarity and, commonly, loss of superficial cells, marked
variation of all nuclear parameters, and usually numerous irregularly
distributed mitoses (Figure 5). |
