Lab 3: Necrosis

Question 1

1. What is this tissue’s location?
2. What type of necrosis is present here?
3. Why?

Answer 1

1. Pancreas
2. Liquefactive necrosis
3. The diffuse loss of pancreatic tissue (unidentifiable) and the presence of edema (fluid), hemorrhage, calcification, and inflammation are characteristic of liquefactive necrosis.
   
   • This lesion progressed from coagulative necrosis to liquefactive necrosis

Question 2

What is generally seen at 1

2?

Answer 2

1. The loss of pancreatic tissue is replaced by edema (clear spaces),
2. hemorrhage, calcification, and a marked inflammatory infiltrate (mostly neutrophils).

There is diffuse loss of pancreatic lobules. In the upper right hand corner there is several pancreatic lobules that still retain somewhat of their normal architecture.

Question 3

Why would liquefactive happen in the pancreas

Answer 3

• This is a case of acute necrotizing pancreatitis.
• Dogs that are left unsupervised well get into the trash for a quick meal and end up in the emergency clinic for pancreatis.
• The high fat meal causes intrapancreatic activation of phospholipase A and elastase by trypsin which causes autolytic digestion of the pancreas and surrounding tissues, as well as the release of inflammatory mediators.
• This in turn, causes pancreatitis and inflammation of surrounding tissue

Question 4

• What tissue is this?

1. what is seen here
2. ?
3. ?

Answer 4

• pancreas
  1. Dystrophic calcification
  2. inflammation (degenerate neutrophils)
  3. autolytic red blood cells

Question 5

1. What type of necrosis does dystrophic calcification occur in?
2. Why does it happen?
3. What is the significance of finding dystrophic calcification
4. Where would dystropihc calcification generally happen in the pancreas?

Answer 5

1. Dystrophic calcification occurs in areas of necrosis, no matter the type of necrosis-coagulative, caseous, liquefactive, or fat necrosis, but is minimal in liquefactive necrosis.
2. Dead and dying cells can no longer regulate the influx of calcium into their cytosol, and calcium accumulates in the mitochondria.
3. The significance of dystrophic calcification is an indication of a previous injury to a tissue.
4. The dystrophic calcification occurs in the peripancreatic fat within areas of fat necrosis.

Question 6

1. What tissue is this?
2. what is arrow pointing to?
3. why does this happen?

Answer 6

1. Pancreas
2. multifocal areas of saponification.
3. Pancreatitis is also associated with saponification of fat (grossly it appears as white chalky areas, which is the result of breakdown of fat, which produces free fatty acids that interact with calcium)

Question 7

What is seen here?

Answer 7

• Fat necrosis: Shadow outlines of dead fat cells.
• Mineralization is often more basophilic than this example, but the pattern is similar.

Question 8

1. This tissue is obliterated beyond recognition but try and guess what is its location?
2. What type of necrosis is happening here (arrow)

Answer 8

1. lung, tuberculosis caused by mycobacteria
2. caseous necrosis with central basophilic areas of dystrophic calcification.
   • Note the amorphous eosinophilic coagulum in these caseous lesions.

Question 9

Why is caseation sometimes seen in mycobacterial infections?

Answer 9

• Mycobacteria have a complex cell wall with a waxy coat that is quite resistant to killing by phagocytes.
• Macrophages easily ingest these bacteria but when they try to kill them (fusion of lysosome with the phagosome) they are not successful and the macrophage often ends up killing itself.
• This allows the bacteria to become extracellular again and ruptured cells release lytic cell components (such as lysosomal enzymes) which damage more cells and more tissue, hence caseation necrosis.

Question 10

So what is the histomorphologic diagnosis in the bovine with lung tuberculosis?

Answer 10

Severe chronic multifocal granulomatous pneumonia (with caseation necrosis)

Question 11

This is the bovine with severe chronic multifocal granulomatous pneumonia (with caseation necrosis)

1. what is 1
2. ?
3. ?

Answer 11

1. Multinucleate giant cells (syncytia of macrophages)
2. Neutrophils
3. Fibrosis and necrosis

Question 12

1. What tissue is this?
2. What is the best term to use to describe this change?
3. What are consequences to the horse?

Answer 12

1. squamous portion of the stomach
2. Ulceration; multifocal gastric ulcers
3. Discomfort, reduced digestive ability, risk of larger ulcers forming.

Question 13

What has happened here?

Answer 13

Hoof has been sloughed off.

Question 14

what is this

Answer 14

Normal coronary band structure

Question 15

1. what is this
2. What type of necrosis?

Answer 15

1. Affected coronary band in where the hoof has sloughed off
2. coagulative necrosis
   
   • Notice that the tissue is still identifiable

Low magnification view of coronary band and epidermal junction.

Question 16

1. What is this an image of?
2. what is seen here?
3. ?
4. ?
5. What type of necrosis is generally seen?

Answer 16

1. Higher magnification of coronary band lesion
2. Changes of ballooning cell degeneration,
3. pyknosis
4. loss of nuclei
5. with loss of tissue structure is characteristic of coagulative necrosis. Notice that the tissue is still identifiable.

Question 17

What is pyknosis?

Answer 17

the irreversible condensation of chromatin in the nucleus of a cell undergoing necrosis

Question 18

Signalment and history: This is tissue from a canine that was diagnosed with vegetative valvular endocarditis

1. What organ is this
2. Where is the lesion located?
3. What is the lesion called?

Answer 18

1. Kidney
2. Renal cortex
3. renal infarct

Question 19

What is 1

2

Answer 19

1. Renal infarct
2. Line of demarcation

Question 20

Describe the changes

Answer 20

• There are multifocal areas of firm, irregularly shaped, dark red discoloration of the renal parenchyma.
• These areas are surrounded by a pale margin.
• This discoloration is present in the renal cortex and extends into the renal medulla.

In the example in lab, the whole kidney was a light brown color, with green discoloration of the medulla, likely due to artifact from fixation

Question 21

1. What type of necrosis?
2. Explain how this happens in the kidney?

Answer 21

1. coagulation necrosis.
   
   • Note that the integrity of the tissue is retained, especially in relation to previous examples we have had of caseation of liquefactive necrosis
2. These are renal cortical infarcts and are basically areas of coagulative necrosis that occur secondary to obstruction of the blood supply (generally arcuate or interlobular arteries).

Question 22

Signalment and History: “Caesar”, a neighborhood stray named for his progressively enlarging ‘roman nose’, was found in respiratory distress and expired en-route to a veterinary clinic.

• Describe the lesion.

Answer 22

• Elevating the pleura and invading the pulmonary parenchyma are multifocal to widely disseminated light-tan nodules.
• These nodules measure from .1-.5cm in diameter, are slightly firmer than the surrounding parenchyma.
• On cut surface, the nodules appear reticulated (net-like, or spongy), and contain somewhat grainy (caseous) material.

Question 23

List 3 common general differentials for pulmonary nodules

Answer 23

1. Abscess
2. Granuloma
3. Neoplasia

(Nodular hyperplasia is not commonly seen in the lungs. Think kidney, spleen and pancreas for this change, as well as ‘labile’ epithelial tissues)

Question 24

1. What type of necrosis?
2. What are arrows pointing to?

Answer 24

1. caseous necrosis.
2. Caseous granulomas

Question 25

1. How can caseous granulomas in the lungs of cats happen?
2. Why can the “roman nose” be seen?

Answer 25

1. caused by bacterial (Mycobacterium bovis, tuberculosis or avium),
   
   • mycotic (Cryptococcus neoformans)
   • parasitic (Aelurostrongylus abstrusus)
   • This is an example of cryptococcal pneumonia.
2. The ‘roman nose’ (see picture) observed in the signalment is a common manifestation of granulomatous rhinitis seen with this disease, as the fungus can be harbored within the nasal passages of even healthy animals.

Question 26

Signalment and history: This is tissue from a steer with lameness on fescue pasture.

• Describe the lesion.

Answer 26

• Affecting the distal extremities, there are locally extensive, moderately well demarcated areas of skin loss which reveals underlying smooth, reddened, moist subcuticular tissue (ulceration).
• The overlying epidermis is irregular, brown to black, and firm with a rough and dry surface.

Question 27

Signalment and history: This is tissue from a steer with lameness on fescue pasture

1. What type of necrosis does this represent?
2. How does this happen?

Answer 27

1. dry gangrene
2. In dry gangrene, after necrosis, the tissues are depleted of water and this dehydration results in mummification.
   
   • In this case, fescue toxicity caused vasoconstriction of vessels in the distal extremity.
   • There is little proliferation of bacteria since dry tissues do not provide an environment favorable to their growth.

Question 28

Signalment and history: This tissue is from a 2-yr old Holstein cow with a history of pneumonia.

1. What organ is this?
2. Describe the lesion.

Answer 28

1. Abomasum
2. Multifocally, there are round regions of mucosal loss and exposure of the underlying submucosa (ulcerations), ranging in size from 1mm-1.5cm diameter.
   
   • The periphery of the ulcerated areas is raised and hyperemic.

Question 29

Signalment and history: This tissue is from a 2-yr old Holstein cow with a history of pneumonia.

1. What is the name for this lesion?
2. How can this happen?
3. What is a common presenting clinical sign?
4. What happens if it perforates?

Answer 29

1. Multifocal abomasal ulcers.
2. Causes of abomasal ulcers in cattle include infectious pathogens (eg. viruses, bacteria and fungal agents), metabolic disturbances, stress and foreign bodies.
3. A common presenting clinical sign of affected animals is melena (blood in the feces).
4. With perforation, hemorrhage into the peritoneal cavity and/or septic peritonitis can occur and result in death. In this case, the ulcers were caused by fungal associated thrombi.

Question 30

Signalment and History: This tissue is from a 700 pound Angus steer that has had a short duration of ataxia and now is unable to rise

• Describe the lesion.

Answer 30

• There are multiple locally extensive areas of cerebral gray matter characterized by thinning and fragmentation of the gray matter.
• In many of these regions, there is separation of the gray matter from the underlying white matter forming prominent clefts.
• The gray matter in these areas is mildly discolored (tan to yellow).

Question 31

1. What type of necrosis does this represent?
2. Why does this happen?

Answer 31

1. This is an example of liquefactive necrosis.
2. This represents the typical necrosis type in the CNS due to rapid enzymatic dissolution of the neuropil (high lipid membrane content here).
   
   • The result is a cavity filled with lipid debris and fluid.
   • This is actually more easily appreciated histologically; however the thinning gray matter and cleft formation are big clues of the process that is occurring here.
   • In other tissues, liquefactive necrosis can look different (see other cases and think abscesses).

Question 32

If this is a bovine with polioencephalomalacia how does this happen?

Answer 32

• This is a case of nutritional polioencephalomalacia, a disease commonly seen in growing ruminants that is associated with thiamine deficiency.
• Polio (cerebrocortical necrosis) can have a variety of causes including excess dietary sulfur, proliferation of thiaminase-producing bacteria, excessive intake of thiamine antagonists (amprolium or bracken fern), subacute to chronic lead toxicosis or water deprivation/sodium toxicosis.

Question 34

Signalment and History: Tissues from adult ewes in poor body condition; one exhibited depression and ataxia for 4-6 weeks, and the other was dyspneic.

1. What tissue is this?
2. describe the lesion

Answer 34

1. Mediastinal lymph nodes:
2. The lymph nodes are markedly enlarged, encapsulated by firm white (fibrous) tissue, and contain tan/white, friable material with concentrically laminated (onion-skin) appearance and cavitated centers.

Question 35

1. What type of necrosis?
2. How does this happen?

Answer 35

1. caseation necrosis.
2. Remember, caseation necrosis implies the conversion of dead cells into a granular friable mass that still is somewhat solid and often resembles cottage cheese.
   
   • The abscesses within the myocardium and the cerebrum could also fit in the liquefactive necrosis category due to their liquified centers.
   • These are example of caseous lymphadenitis (CLA) of sheep that is caused by the bacterium Corynebacterium pseudotuberculosis.
   • Compared to coagulation necrosis, this lesion is an older (chronic) one as evidenced by the fibrous capsule (more on this later).