In HE sections, features common to xenografts of brain metastasis included: a) sharp boundary between tumor mass and surrounding normal brain tissue (Figure 4A and 4B); b) round and densely arranged tumor cells; c) abundant caryocinesia; d) abundant acid mucus secretion by tumor cells that were dyed blue by Alcian blue and red by PAS; e) positive immunostaining for CEA (Figure 5A and 5B). Here, CEACAM5 is linked to neoplasm.