Collision tumor of the kidney composed of clear cell carcinoma and collecting duct carcinoma treated with cabozantinib and nivolumab oleh Carlos Eduardo Salazar-Mejía, Víctor Manuel Oyervides-Juárez, Blanca Otilia Wimer-Castillo, Oscar Vidal-Gutiérrez, Raquel Garza-Guajardo, Enrique Grande