Pathologica 4-07.pdf - Pacini Editore

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nuclear atypia irrespective of cell thickness. The urothelium
lining the papillae is similar to flat hyperplasia 15 32 . The major
distinction from papilloma is that in papillary urothelial neoplasm
of low malignant potential the urothelium is much
thicker and/or nuclei are significantly enlarged. The urothelial
papilloma, in contrast, has no architectural or cytological atypia.
Mitotic figures are infrequent in papillary urothelial neoplasms
of low malignant potential, and usually limited to the
basal layer. This lesion is not associated with invasion or
metastases, except in rare cases 33 . These patients are at an increased
risk of developing recurrent or new papillary lesions.
These new lesions occasionally are of higher grade and may
progress.
Papillary urothelial carcinoma, low-grade. A papillary
urothelial lesion with an overall orderly appearance but with
easily recognizable variation of architectural and or cytological
features seen at scanning magnification 15 . Variation of
polarity and of nuclear size, shape, and chromatin texture are
the hallmark of the lesion. Mitotic figures are infrequent and
usually seen in the lower half of the urothelium. The urothelium
lining the papillae is similar to flat dysplasia. Tangential
sections near the base of the urothelium may be misleading
since result in sheets of immature urothelium with frequent
mitotic activity. A spectrum of cytological and architectural
abnormalities may exist within a single lesion, stressing the
importance of examining the entire lesion and noting the
highest grade of abnormality 34 .
Papillary urothelial carcinoma, high-grade. A papillary
urothelial lesion with predominantly or totally disorderly appearance
at low magnification with both architectural and cytological
abnormalities. The epithelium is disorganized and
there is a spectrum of nuclear pleomorphism ranging from
moderate to marked. The nuclear chromatin tends to be
clumped and nucleoli may be prominent. Mitotic figures, including
atypical forms, are frequently seen at all levels 2 . The
urothelium lining the papillae is similar to flat CIS. In tumors
with variable histology, the tumor should be graded according
to the highest grade.
High-grade papillary urothelial carcinomas have a high risk
of progression and of association with invasive disease at the
time of diagnosis 35 36 .
Relation of WHO 1973 to WHO 2004. A major misconception
is that there is a one to one translation between the
WHO 2004 and the WHO 1973 classification systems. Only
at the extremes of grades in the WHO 1973 classification
does this correlation hold true 2 37-40 . Lesions called papilloma
in the WHO 1973 classification system would also be
called papilloma in the WHO 2004 system. At the other end
of the grading extreme, lesions called WHO grade 3 are by
definition high-grade carcinoma in the WHO 2004 system.
However, for WHO grades 1 and 2, there is no direct translation
to the WHO 2004 system. Lesions classified as WHO
grade 1 in the 1973 system, showing no cytological atypia,
some nuclear enlargement and merely thickened urothelium,
are included in the group of papillary urothelial neoplasms
of low malignant potential in the WHO 2004 system
while other WHO grade 1 lesions showing slight cytological
atypia and mitoses, are diagnosed in the WHO 2004 system
as low-grade papillary urothelial carcinomas. WHO
grade 2 includes either relatively bland lesions that in the
WHO 2004 system would be called low-grade papillary
urothelial carcinoma or higher grade lesions, which in many
institutions are called WHO grade 2-3. These lesions in the
WHO 2004 classification system would be called highgrade
papillary urothelial carcinoma.
SLIDE SEMINAR JUNIORES
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