Uroplakins Ia, Ib, II and III are structural proteins of urothelial cells differentiated. In non-neoplastic urothelial cells, Uroplakins are expressed in the luminal membrane of surface cells. Uroplakin III has been shown to be a standard marker for confirmation of urothelial carcinoma due to its high specificity. On the other hand, its sensitivity has been described as being moderate.
A recent study highlight that Uroplakin II has a sensitivity of 78% versus 34% for Uroplakin III with identical specificity.
Therefore, Uroplakin II is considered as an excellent marker for the identification of urothelial cancers in patients with Carcinoma with Unknown Primary tumor syndrome.