Cellular Pathology Gross Pathology Laboratory 2 Cell Injury. VPM 152: General Pathology Instructor: Chelsea Martin Winter 2016

Transcription

1 Cellular Pathology Gross Pathology Laboratory 2 Cell Injury VPM 152: General Pathology Instructor: Chelsea Martin Winter 2016

2 Gross Specimens The following slides consist of images from the specimens presented during the laboratory and are used as examples of cell injury and necrosis The tissues are formalin fixed, which alters the gross appearance of lesions Congestion and hemorrhage appear brown-to-back, depending on the severity Liquid exudate (pus) can be washed away, leaving cavities, or can become solid and crumbly, and may appear similar to caseous necrosis. Pay attention to additional information in order to help you arrive at an appropriate interpretation (you may be provided with a description of what the material looked like prior to fixation, microscopic images or a description of the microscopic features) If asked to describe a formalin-fixed lesion, just describe the colors and textures as you see them Many examples of necrosis are inflammatory in nature but we have not covered inflammatory pathology yet. These slides contain some inflammation-related terminology which will be more clear later in the course. Right now, just focus on lesions of cell injury and necrosis.

3 Liver from an adult obese cat with recent history of anorexia. Description: The liver is diffusely and markedly pale, diffusely and moderately enlarged, and the lobe margins are rounded. (The texture is greasy, and the parenchyma bulges when the liver is cut) Morphologic diagnosis: Hepatic lipidosis, diffuse, severe (or marked). Abnormal liver Pathogenesis: 1. Increased lipid uptake: Delivery of excess fatty acids to liver (Increased dietary fat, or starvation causes increased mobilization of fat) 2. Impaired metabolism: Reduced oxidation of fatty acids into ketones (due to hypoxia, toxins) 3. Reduced export: Insufficient apoprotein for shuttling triglycerides out of liver as lipoprotein (starvation reduces protein synthesis, hypoxia and certain toxins can impact this as well) Differential diagnosis for pale, swollen liver? Steroid hepatopathy: corticosteroid administration leads to glycogen accumulation in liver. It is pale (not this pale) and swollen but is not greasy. Normal liver

4 Small intestine and mesentery from a 17 year old cat with evidence of pancreatic necrosis ( pancreatitis ). Description: On the surface of mesenteric fat, there are multifocal-to-coalescing, variably sized areas of opaque white discoloration. Morphologic diagnosis: Mesenteric fat necrosis (enzymatic), multifocal, marked. What process is causing the gross changes? Leakage of digestive enzymes from the necrotic pancreas digests adjacent tissue (autodigestion). This causes mineral deposits in the necrotic fat (Saponification).

5 Mesenteric fat and intestine from an adult cow. Description: The mesentery is markedly expanded by adipose tissue that is uniformly very firm and rigid, which surrounds the spiral colon. Morphologic diagnosis: Mesenteric fat necrosis (massive), diffuse, marked. Consequence: Intestinal stenosis and obstruction, dystocia due to space occupying mass in abdomen.

6 Spleen from a 6-month old dog. Vasculitis and vascular necrosis were observed in the spleen. Note the areas of pallor (circled on next slide). Description: There are multiple areas of spleen parenchyma that demonstrate mild to moderate pale tan discoloration. These areas correspond to slightly raised areas on the capsular surface (lack of splenic contraction). Additional information: Microscopically, these areas are hypereosinophilic and have no nuclear staining, yet the outline of the splenic architecture is preserved. What type of necrosis is this? Coagulative necrosis (ischemic necrosis, infarct) Morphologic diagnosis: Multifocal splenic coagulative necrosis (splenic infarcts)

7 Spleen from a 6-month old dog. Vasculitis and vascular necrosis were observed in the spleen. Note the areas of pallor. Description: There are multiple areas of spleen parenchyma that demonstrate mild to moderate pale tan discoloration. These areas correspond to slightly raised areas on the capsular surface (lack of splenic contraction). Additional information: Microscopically, these areas are hypereosinophilic and have no nuclear staining, yet the outline of the splenic architecture is preserved. What type of necrosis is this? Coagulative necrosis (ischemic necrosis, infarct) Morphologic diagnosis: Multifocal splenic coagulative necrosis (splenic infarcts)

8 Kidney from a 12-year-old cat with an enlarged heart and a markedly enlarged left atrium. Description: There are two areas of pale tan discoloration in the renal cortex, associated with a reddish brown rim of discoloration at the edges of the lesion. The capsular surface of these discolored areas are slightly depressed compared to the adjacent tissue. Additional information: Microscopically, these areas consist of typical renal cortical architecture yet is hypereosinophilic and has lost nuclear staining. There is a rim of hemorrhage and inflammatory cells at the periphery of the lesion. What type of necrosis is this? Coagulative necrosis (ischemic necrosis, infarct). With time, this may progress to caseous necrosis (loss of architecture), and then replacement with fibrous connective tissue (scar) Morphologic diagnosis: Multifocal renal cortical ischemic necrosis (infarcts) Relationship to heart? Fibrin thrombi form in dilated left atrium, which break apart sending small thrombi to distant sites (emboli). Small thrombi lodge in renal vasculature, resulting in ischemic necrosis.

9 Pig, sudden death. Note the sunken, pale area of left ventricular myocardium. On cut surface, this area of myocardium is markedly reduced in thickness. (circled on next slide). Microscopically, there is loss of myofibers and replacement with fibrous connective tissue (scar). Is this an acute or chronic process? Chronic What other lesions would you expect? Lesions of congestive heart failure (pulmonary congestion and edema) Cause? Unknown, but probably a prior systemic infection progressed to sepsis and formation of fibrin thrombi, lodging in a cardiac artery and resulting in ischemic necrosis. Over time, the necrotic material was removed and replaced with fibrous connective tissue.

10 Pig, sudden death. Note the sunken, pale area of left ventricular myocardium. On cut surface, this area of myocardium is markedly reduced in thickness. Microscopically, there is loss of myofibers and replacement with fibrous connective tissue (scar). Is this an acute or chronic process? Chronic What other lesions would you expect? Lesions of congestive heart failure (pulmonary congestion and edema) Cause? Unknown, but probably a prior systemic infection progressed to sepsis and formation of fibrin thrombi, lodging in a cardiac artery and resulting in ischemic necrosis. Over time, the necrotic material was removed and replaced with fibrous connective tissue.

11 Brain from a 1-year old heifer with a recent and progressive history of head-tilt, drooping ear and blindness. Listeria monocytogenes was cultured from the lesion. When fresh, this area contained tan opaque fluid. Histologically, there is loss of tissue and the adjacent areas are infiltrated with inflammatory cells (neutrophils). Gross description: On cut surface of the brainstem, there is a unilateral, focal area where the tissue is softened and partially lost. What type of necrosis is this? Liquifactive (this type of necrosis is typical of the CNS) Morphologic diagnosis: Encephalitis, suppurative, focal, acute, marked. (This morphologic diagnosis captures the microscopic findings of inflammation, which will be covered at a later date)

12 Liver from a calf with severe omphalophlebitis and arteritis (inflammation of umbilical vein and arteries). When fresh, the cavitated areas contained pale tan opaque fluid. There is a rim of firm, pale tan connective tissue at the margins of the cavitated areas (fibrosis). Microscopically, there are numerous degenerate and necrotic inflammatory cells (neutrophils). Type of necrosis? Liquifactive. Pathogenesis: Ascending bacterial infection from the umbilical vein, or hematogenous spread associated with sepsis, originating from the infected umbilicus. Morphologic diagnosis: Hepatitis, suppurative, multifocal to coalescing, chronic, severe (right now, this is just FYI but we will cover it in the inflammation section).

13 Lungs from a geriatric dog. There are multifocal metastatic carcinomas in the lung (this could represent any type of carcinoma, but mammary carcinoma and thyroid carcinoma would be good possibilities). Note the loss of tissue, with a small amount of irregular, crumbly material remaining. Type of necrosis in center of metastatic tumours: Liquifactive and caseous.

14 Ceolomic cavity (air sacs, heart and lungs) from a bird. Description: There are multifocal-to-coalescing, pale tan, raised, flat circular areas on the surface of the air sacs (arrows). Smaller foci of similar material is scattered throughout the lungs (circled). Additional information: These tan areas are composed of pasty, somewhat crumbly material. Microscopically, it is eosinophilic debris (no recognizable architecture) mixed with dead and dying inflammatory cells (mostly macrophages with some heterophils). Type of necrosis? Caseous. These lesions are typical of a chronic fungal respiratory infection in birds caused by Aspergillus sp. Morphologic diagnosis: Air sacculitis and pneumonia, granulomatous, mulltifocal to coalescing, chronic, marked. (right now, this is just FYI but we will cover it in the inflammation section).

15 Larynx and trachea from young steer with symptoms of pneumonia. Description: The mucosal surface of the trachea is covered by an irregular layer of pale tan material that is adhered to the underlying tissue. (Microscopically, this material is composed of debris, fibrin and dead cells with no preservation of architecture). Type of necrosis: Caseous (though there is likely also liquifactive necrosis here as well) Pathogenesis: Bacterial infection causes necrosis of the epithelium and blood vessels, leading to leakage of plasma and formation of a layer of necrotic tissue and fibrin adhered to the surface of the trachea, forming a pseudomembrane. Morphologic diagnosis: Tracheitis, necrotizing, locally extensive, acute, marked. (right now, this is just FYI but we will cover it in the inflammation section).

16 Lungs from a geriatric dog. Prior to fixation, there were multifocal to coalescing areas of pale tan discoloration alternating with areas of deep red discoloration (congestion and hemorrhage). (Lesions are circled on next slide). Additional information: The pulmonary arteries contained grey thrombi. Microscopically, the pale areas correspond to areas of hypereosinophilia and loss of nuclear staining yet alveoar architecture is preserved. Type of necrosis: Coagulative necrosis (ischemic necrosis, infarct)

17 Lungs from a geriatric dog. Prior to fixation, there were multifocal to coalescing areas of pale tan discoloration alternating with areas of deep red discoloration (congestion and hemorrhage). Additional information: The pulmonary arteries contained grey thrombi. Microscopically, the pale areas correspond to areas of hypereosinophilia and loss of nuclear staining yet alveoar architecture is preserved. Type of necrosis: Coagulative necrosis (ischemic necrosis, infarct)

18 Aorta Lymph node Mediastinal lymph node from adult ewe with weight loss and difficulty breathing. The ewe had multiple enlarged lymph nodes and pneumonia. Culture revealed Corynebacterium pseudotuberculosis. Description: the lymph node is replaced with concentric layers of pale tan, crumbly material. What type of necrosis is this? Caseous. Morphologic diagnosis: Lymphadenitis, suppurative (caseating), chronic, diffuse, marked (FYI until covered in inflammation section). This disease is called Caseous lymphadenitis.

19 Lymph node from an adult cow with infected with Mycobacterium bovis (tuberculosis). Description: On cut surface of the lymph node, there are variably sized areas where the normal tissue is replaced by pale tan crumbly material. Type of necrosis: Caseous necrosis, empty spaces indicate smaller areas of liquifactive necrosis. Morphologic diagnosis: Lymphadenitis, granulomatous, multifocal, chronic, marked. (FYI until covered in inflammation section).

20 Mink tail Description: The tail is alopecic, very firm and the remaining tissue is irregular with areas of missing tissue. Type of necrosis: Gangrenous The pathogenesis of this lesion is unknown. Gangrenous necrosis is typical of ischemic necrosis to an extremity, characteristic of frost bite, physical obstruction of vasculature (string / wire wrapped around extremity), certain bacterial infections, toxicities and vascular diseases.