Nested Variant of Urothelial Carcinoma: A Review and Update of the Literature

Background: Nested Variant of urothelial Carcinoma was added to the World Health Organization’s classification in 2004 as a new variant.

Aims: To review the literature on nested variant of urothelial carcinoma.

Results: About 200 cases of Nested variant of urothelial carcinoma have been reported so far and the tumour has the ensuing morphological features: Large numbers of small confluent irregular nests of bland-appearing, closely packed, haphazardly arranged, poorly defined urothelial cells which infiltrate the lamina propria and the muscularis propria.

The tumour which has a bland histomorphology appearance, is reported to have an aggressive biological behaviour.

Because of the tumour’s bland appearance, it has been at times mis-diagnosed as a benign lesion which had led to a significant delay in the establishment of the correct diagnosis and contributing to the advanced stage of the disease.

Immunohistochemically, the tumour shares some characteristic features with high-risk conventional urothelial carcinomas such as, high proliferation index, and loss of p27 expression. However, p53, bcl-2, or EGF-r immunoreactivity is not frequently seen.

The tumour must be differentiated from a number of proliferative lesions of the urothelium

Conclusions: Correct and early diagnosis of this tumour is essential in order to provide early curative treatment in order to avoid diagnosis at an advanced stage. A multi-centre trial is required to identify treatment options