Answer: Carcinoma in situ

Histology: There is a single row of cells that are tenuously holding on to the basement membrane. These cells have enlarged hyperchromatic nuclei with moderate amount of densely eosinophilic cytoplasm. Focally there is a small detached cluster of atypical urothelial cells one which contains a mitotic figure. The surrounding urothelium is entirely denuded.

Discussion: This is a classic example of urothelial carcinoma in situ (CIS) with marked denudation also known as clinging CIS or to clinicians as “denuding cystitis”. CIS cells have a marked tendency for shedding into the urine, hence the value of urine cytology for its detection. In some cases, pathologists are presented with entirely denuded specimens. In these cases we add a note to our diagnosis that “denudation may sometimes reflect cases of CIS where the neoplastic cells have shed as a result of discohesion. Additional tissue and or cytology samplings may be helpful if clinically indicated.” J Urol, 166:457-60, 2001). In some cases where denudation has been partial, one is left with only a few CIS cells clinging onto the basement membrane. The diagnosis of CIS is based on the presence of malignant cells in any quantity regardless of thickness of cell layers involved. In this case, there are cells with hyperchromatic enlarged nuclei more than 4 to 5 times the size of stromal lymphocytes which are diagnostic of CIS, even though there are only scant malignant cells present.