Figure 6a. (a) Transverse section of mammary tissue from the chronic animal shows central gray area that was firm on palpation (outlined by markers) compared with the adjacent tissue. Necrotic tissue was not evident. (b) Photomicrograph obtained in the chronic animal shows aggregated mononuclear cells (arrow) surrounded by densely cellular fibroblastic tissue in fibrotic zone. (Hematoxylin-eosin stain; original magnification, x200.)