Carcinoma in situ: comments on the pathobiology of a paradox.

Carcinoma in situ of the urinary bladder has been recognized as a pathologic entity for over a quarter of a century, yet its biologic and clinical significance is controversial. It has been established that the presence of areas of carcinoma in situ in bladders harboring tumors heralds a relatively poor prognosis. However, the prognostic significance of carcinoma in situ in patients without prior or current solid tumors remains open to question. From the standpoint of cancer biology, the possibility that a morphologic mimicker of carcinoma in situ lacks the metabolic machinery or crucial structural components required to complete the process of neoplastic transformation raises interesting cells. The term carcinoma paradoxicum is introduced to describe functionally benign but morphologically anaplastic intra-epithelial neoplasms with marginal malignant potential.