Figure 1.

(A) Normal lung. Immunostaining for CD31 (antibody JC70) demonstrates the capillaries (in red) of the normal alveoli. (B) An angiogenic tumor: The normal lung architecture is diffusely replaced. New vessels (in red) and stroma are produced intimately mixed with neoplastic cells but without any recognizable architectural structure. (C) A nonangiogenic tumor. Section of lung in which a carcinoma is growing by filling the alveolar spaces: staining for CD31 shows the co-opted alveolar vessels highlighting the normal lung architecture. In this case the pattern is present throughout the whole lesion.