<prompt> A metastatic carcinoma in the brain of an adult, most often comes from a primary in the:StomachOvaryOral cavityLung  <response>: Metastatic carcinoma in the brain of an adult, most often comes from a primary in the Lung. The five most common primary sites are lung, breast, skin melanoma, kidney, and gastrointestinal tract, accounting for about 80 of all metastases. 