Urological pathologists representing the World Health Organization and the
International Society of Urological Pathology have reached a new consensus
on the definitions of flat, non-invasive lesions of the urothelium. Lesions
are classified as: (1) carcinoma in situ (CIS); (2) dysplasia; (3) atypia
of unknown significance; and (4) reactive atypia. These terms are intended
to describe a histological spectrum of architectural and cytological abnorm
alities ranging from the unequivocally malignant (CIS) through the probably
neoplastic (dysplasia) to the benign (atypia). The biological potential of
these lesions in individual patients cannot be accurately predicted, altho
ugh the degree of risk for an adverse outcome is very likely to be proporti
onal to the degree of architectural and cytological anaplasia. It is likely
that each phenotype has two biological potentials: dynamic and effete. It
should be emphasized that most of our knowledge concerning these lesions in
humans has been obtained from studies of groups of patients who have alrea
dy developed a papillary or nodular, invasive or non-invasive urothelial ca
rcinoma, as descriptions of primary CIS, dysplasia, and atypia are uncommon
. Future knowledge in this area might be enhanced by attention to the follo
wing:
better definitions of terms and more accurate application of words such as
bladder cancer, early lesion, tumor progression, precursor, and premalignan
t;
increased understanding of the biological processes underlying phenotypic c
hanges;
development of models (probably computer-based) with the capacity to factor
in the complexities of human carcinogenesis in an ongoing fashion, as new
information becomes available.