Liquefactive
• See this in infections and, for some unknown reason, in brain infarcts
• Due to lots of neutrophils around releasing their toxic contents, “liquefying” the tissue
• Gross: tissue is liquidy and creamy yellow (pus)
• Micro: lots of neutrophils and cell debris
Fat necrosis
• See this in acute pancreatitis
• Damaged cells release lipases, which split the triglyceride esters within fat cells
• Gross: chalky, white areas from the combination of the newly-formed free fatty acids with calcium (saponification)
• Micro: shadowy outlines of dead fat cells (see image above); sometimes there is a bluish cast from the calcium deposits, which are basophilic