The nested variant of urothelial carcinoma is a rare histological tumor of urinary bladder. The clinical symptoms are similar to those of the classic urothelial carcinomas. Its macroscopic appearance can be very subtle due to its preference for a submucosal growth leading to a possible delay in diagnosis. Microscopically, it is characterized by nests and tubules formation. While the neoplastic cells exhibit low-grade histological features, the growth pattern is widely infiltrative conferring this neoplasia a bad prognosis even if a radical treatment is performed. We present a case of a patient affected by a nested variant of urothelial carcinoma of urinary bladder to whom a radical cystoprostatectomy was performed and adjuvant chemotherapy was given. He is alive and free of disease one year after the diagnosis.

ResumenEl carcinoma urotelial de vejiga tipo "nested" o en nidos es una variante histológica rara dentro de los tumores uroteliales de vejiga. Aunque las manifestaciones clínicas son semejantes a los demás tumores de vejiga, su apariencia macroscópica puede ser inexpresiva, con crecimiento submucoso difícil de detectar en la cistoscopia, lo que puede retrasar el diagnóstico. Microscópicamente se caracteriza por la distribución celular en forma de nidos y túbulos. Presentan un bajo grado de atipia citológico que simula un carcinoma urotelial de bajo grado, lo que contrasta con un patrón de crecimiento ampliamente infiltrativo que le confiere un mal pronóstico a pesar de tratamientos radicales.Presentamos el caso de un paciente afecto de un carcinoma urotelial de vejiga tipo nested sometido a cistoprostatectomia radical y tratamiento con quimioterapia adyuvante que se encuentra libre de enfermedad un año después del diagnóstico.Palabras clave: Carcinoma de vejiga. Carcinoma urotelial. Nested carcinoma. Nested variant of urothelial carcinoma. A rare histological variant AbstractThe nested variant of urothelial carcinoma is a rare histological tumor of urinary bladder. The clinical symptoms are similar to those of the classic urothelial carcinomas. Its macroscopic appearance can be very subtle due to its preference for a submucosal growth leading to a possible delay in diagnosis. Microscopically, it is characterized by nests and tubules formation. While the neoplastic cells exhibit low-grade histological features, the growth pattern is widely infiltrative conferring this neoplasia a bad prognosis even if a radical treatment is performed.We present a case of a patient affected by a nested variant of urothelial carcinoma of urinary bladder to whom a radical cystoprostatectomy was performed and adjuvant chemotherapy was given. He is alive and free of disease one year after the diagnosis.