Page 62 - Textbook of Pathology, 6th Edition

46

SECTION I

Figure 3.26 Liquefactive necrosis brain. The necrosed area on right side of the field shows a cystic space containing cell debris, while the
surrounding zone shows granulation tissue and gliosis.

Fat necrosis hydrolyses neutral fat present in adipose cells has the staining properties of fibrin. It is encountered in
into glycerol and free fatty acids. The damaged adipose cells various examples of immunologic tissue injury (e.g. in
assume cloudy appearance. The leaked out free fatty acids immune complex vasculitis, autoimmune diseases,
complex with calcium to form calcium soaps (saponification) Arthus reaction etc), arterioles in hypertension, peptic
discussed later under dystrophic calcification. ulcer etc.
Grossly, fat necrosis appears as yellowish-white and firm Microscopically, fibrinoid necrosis is identified by
deposits. Formation of calcium soaps imparts the necrosed brightly eosinophilic, hyaline-like deposition in the vessel
General Pathology and Basic Techniques
foci firmer and chalky white appearance. wall. Necrotic focus is surrounded by nuclear debris of
Microscopically, the necrosed fat cells have cloudy neutrophils (leucocytoclasis) (Fig. 3.29). Local haemor-
appearance and are surrounded by an inflammatory rhage may occur due to rupture of the blood vessel.
reaction. Formation of calcium soaps is identified in the
tissue sections as amorphous, granular and basophilic APOPTOSIS
material (Fig. 3.28).
Apoptosis is a form of ‘coordinated and internally
5. FIBRINOID NECROSIS. Fibrinoid necrosis is programmed cell death’ having significance in a variety of
characterised by deposition of fibrin-like material which physiologic and pathologic conditions (apoptosis is a Greek

Figure 3.27 Caseous necrosis lymph node. There is eosinophilic, amorphous, granular material, while the periphery shows granulomatous
inflammation.