Figure 4.

Histopathological examples demonstrating the different tumor cell infiltration patterns and angiogenetic features in the peritumoral brain tissue of brain metastases using hematoxylin and eosin stains under light-microscopy. (A) A well-demarcated growth pattern is present in a patient with a brain metastasis (black arrows) from colorectal cancer without evidence of tumor cell infiltration in the peritumoral brain tissue. (B) In contrast, histopathological assessment demonstrates tumor cell infiltration in the peritumoral brain tissue with either a diffuse “glioma-like” single cell infiltration (black arrows) or (C) growth along pre-existing blood vessels in a “vascular co-option” growth pattern (black arrows) in two patients with known melanoma. (D) Further, histopathological analysis shows presence of angiogenesis with a characteristic multilayered endothelium (black arrows) in the peritumoral brain tissue in a patient with colorectal cancer. (E) Vessels with a single endothelial layer were defined as “no angiogenesis”, (F) whereas angiogenesis is absent in another patient with non-small cell lung cancer.