Clinical and Pathological Features of the Nested Subtype of Urothelial Carcinoma With Lymph Node Metastasis as the Initial Presentation: A Case Report.

The nested subtype of urothelial carcinoma (NS-UC), a rare and aggressive bladder cancer, mimics benign bladder lesions but behaves like high-grade urothelial carcinomas. The author reported a rare case of NS-UC, initially presenting with inguinal lymph node metastasis. The tumor cells of NS-UC exhibit minimal cellular atypia, forming small nests, while the tumor cells of lymph node metastatic carcinoma show greater cellular atypia with diverse structures. Immunohistochemistry is helpful in determining the origin of lymph node metastatic carcinoma. NS-UC often presents morphologically similar to benign lesions, which should be given sufficient attention.