Nested Variant of Urothelial Carcinoma: A Review and Update of the Literature
DOI:
https://doi.org/10.9734/bpi/rtcms/v9/1627FKeywords:
Nested variant, urothelial carcinoma, bland –appearing, lamina-propria-infiltration, muscularis-propria-infiltration, confluent-irregular-nests, high-proliferation-index, loss-of-p27 expressionAbstract
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 that would improve the outcome of this tumour.
