Fig. 15.21 Histology of invasive papillary urothelial carcinoma of
bladder. Arrow points to invasion of stalk (H&E x LP).
Fig. 15.23 Urothelial cells showing instrumentation artifact
(Papanicolaou x MP).
Fig. 15.22 Histology of bladder papillary urothelial carcinoma,
moderately differentiated grade II. The papilla is still frond-like, but the
tumor cells contain enlarged, moderately irregular, and hyperchromatic
nuclei (H&E x MP).
Papillary Urothelial Tum or Grade I
Papillary neoplasms of low malignant potential differ only slightly
from transitional cell papillomas; they are usually somewhat larger
and have a slightly greater degree of cytologic atypia. Similarly, the
cytologic findings differ only slightly. In most cases, the urine sam-
ples are more cellular than normal, and an average of 15 cohesive
clusters of four or more cells are present per 1000 cells, approxi-
mately eightfold the number of clusters found in normal voided
control urine samples. The increase in the number of cell clusters
in voided urine may suggest the possibility of a low-grade papillary
tumor, but this does not apply to bladder washings, which always
are more cellular and contain many clusters. The cell clusters in
low-grade papillary tumors tend to be irregular and with ragged
borders, in contrast to the cohesive, ball-shaped papillary clusters
with smooth borders found after instrumentation29 (Figs 15.23
and 15.24). As in papillomas, some of these cells are elongated
and have oval but still relatively small and bland, only slightly
hyperchromatic nuclei (Fig. 15.25). Nucleoli are present in approx-
imately 25% of the nuclei. The nucleoplasm of slightly more than
half of the nuclei is finely granular or opaque. The single cells
Fig. 15.24 Papillary cluster and single urothelial cells from low-grade
papillary urothelial carcinoma of bladder. Minimal changes consist
of a decreased amount of cytoplasm and slight variability of nuclear size
(Papanicolaou x MP).
present also resemble normal or reactive cells and do not show
definite criteria of malignancy as seen in higher grade tumors (Fig.
15.26). Red blood cells may be increased in number. A cytologic
diagnosis is only rarely possible, usually in cases in which the urine
is particularly cellular and numerous clusters of moderately atypi-
cal cells are present. These findings may be considered consistent
with low-grade papillary carcinoma, especially if the patient had
such lesions in the past and previous biopsy specimens are avail-
able for comparison. In specimens that contain only few clusters,
distinction from reactive papillary hyperplasia of the type that may
be associated with calculi is often not possible (see Fig. 15.18). A
report may briefly comment on the presence of increased numbers
of cells and cell clusters and state that "low-grade papillary tumor
must be considered" or "cannot be excluded."
Key features of papillary urothelial tumor grade I
• Increased number of cell clusters (voided urine);
• Cell clusters with ragged borders;
• Slightly hyperchromatic nuclei; and
• Occasional nucleoli.