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SYSTEMIC PATHOLOGY - 1 > 17b – Thymus and Spleen > Flashcards

17b – Thymus and Spleen Flashcards

1
Q

What are the 4 things that can cause splenic infarcts?

A
  1. Vascular damage: certain viruses (classical swine fever) and bacterial sepsis
  2. Hypercoagulable states
  3. Splenomegaly (of any cause)=more prone to thrombosis and infarction
  4. Septic emboli (ex. endocarditis of left heart)
    *first 3=due to thrombosis
    *ISCHEMIC NECROSIS
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2
Q

What are some examples of hypercoagulable states?

A
  • Nephrotic syndrome
  • IMHA
  • Steroid therapy/Cushing’s disease
  • Neoplasia
  • Pancreatitis
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3
Q

What are the GROSS lesions of splenic infarcts?

A
  • Acute
    o discrete, slightly raised and dark red areas at the margins of organ
  • With time
    o Depressed, pale and firm (fibrosis)
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4
Q

Splenic hematoma

A
  • Common in dogs
  • Trauma
  • Often associated with nodular hyperplasia or splenic vascular neoplasia
  • *NEED histology to rule out underlying neoplasia (especially hemangiosarcoma)
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5
Q

Splenic hematoma GROSSLY

A
  • Red nodular mass
  • Very large
  • Soft and dark red on cut surface
  • Bloody consistency
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6
Q

Spleen inflammation: acute splenitis – multifocal necrotic or suppurative splenitis

A
    1. Tularemia (Franciscella tularensis)
    1. Yersiniosis (Yersinia pseudotuberculosis)
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7
Q

Tularemia

A
  • Especially wild rodents
  • Can effect most speices
  • ZOONOTIC
  • Humans: severe systemic disease
  • Penetrate intact skin and mucous membranes
  • Ingestion, inhalation and inoculation by biting insects and ticks
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8
Q

Yersiniosis

A
  • Wild rodents and birds
  • Can affect many species
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9
Q

What does acute splenitis - multifocal necrotic or suppurative splenitis look like GROSSLY?

A
  • Small multifocal miliary WHITE foci within spleen
    o Can see similar lesions in lymph nodes and liver
  • Older lesions: resemble granulomas/abscesses
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10
Q

Spleen inflammation: acute splenitis – septicemic splenitis

A
  • African swine fever
  • Erysipelas
  • Anthrax!
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11
Q

What does acute splenitis – septicemic splenitis look like GROSSLY?

A
  • Splenomegaly
  • Soft
  • Dark discolouration
  • Engorged with viscous blood
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12
Q

Acute splenitis – septicemic splenitis – ANTHRAX

A
  • Disease caused by spore forming bacteria: Bacillus anthracis
  • *zoonotic
  • Horses, pigs, dogs: pharyngeal and enteric disease
  • Ruminants: septicaemic disease
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13
Q

What is the pathogenesis of anthrax in ruminants?

A
  1. Ingestion/wound/contamination/inhalation of spores
  2. Lymphangitis and localized lymphadenitis
  3. Massive bacteria (sepsis) and toxemia
    a. With sepsis: huge numbers of vegetative organisms in blood
  4. Increased vascular permeability and impaired coagulation
  5. Sudden death
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14
Q

Anthrax vegetative organisms in blood

A
  • Become spores when exposed to air
    o Very resistant
    o Survive decades in soil
    o Infections often occur following soil excavation
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15
Q

What are the anthrax lesions in ruminants?

A
  • Bloated autolyzed carcass with blood OOZING from orifices
  • Marked splenomegaly
    o Dark red to black, soft to t semi-fluid spleen
  • Multifocal hemorrhage and edema in connective tissues
  • *thick tarry blood: fails to clot
    o Or clots are very soft and friable
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16
Q

Anthrax in ruminants

A
  • *do NOT necropsy
  • Take a blood smear from ear
    o Methylene blue stain=short chains of large bacilli with distinct pink capsule and square ends
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17
Q

Anthrax in pigs and dogs

A
  • Splenomegaly is NOT characteristic
  • Pharyngeal inflammation with cervical lymphadenitis or localized necrotizing enteritis
  • *acquire infection from eating infected carcasses
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18
Q

Chronic splenitis: Granulomatous splenitis can lead to

A
  1. Nodular granulomatous splenitis
  2. Diffuse granulomatous splenitis
    *caused by similar agents
19
Q

What are some causes of granulomatous splenitis?

A
  • Mycobacterium spp. (ex. tuberculosis)
  • Brucella spp.
  • Systemic mycotic diseases (ex. histoplasmosis and blstomycosis)
  • Leishmania spp.
20
Q

Spleen abscesses

A
  • Rare
  • Secondary to sepsis or septic embolism
  • Ex. Trueperella pyogenes: cattle
  • Ex. Rhodococcus equi: horses
21
Q

What are the 6 types of growth disturbances of the spleen?

A
  • Aplasia
  • Atrophy
  • Benign nodular hyperplasia
  • Lymphoid hyperplasia
  • Hyperplasia of monocyte-macrophage system
  • Extramedullary hematopoiesis
22
Q

Aplasia, malformation or atrophy of spleen

A
  • Little pathological significance
23
Q

Benign nodular hyperplasia

A
  • Common finding in old dogs
  • Usually incidental
  • Unknown cause
  • RULE OUT neoplasia
  • May PREDISPOSE to splenic hematomas
24
Q

Benign nodular hyperplasia GROSSLY

A
  • Single or multiple raised nodules
  • Gray to reddish pink or red and white
  • Usually <2cm, can reach >5cm
25
Q

Benign nodular hyperplasia HISTOLOGICALLY

A
  • Unencapsulated nodules composed of aggregates of lymphoid tissue
  • +/- EMH, separated by congested red pulp
26
Q

Lymphoid hyperplasia

A
  • Hyperplasia of lymphoid follicles and PALS
  • Response to blood-borne chronic antigenic stimulation
  • *lymphoid follicles visible as 1-3 mm WHITE foci scattered throughout the spleen
    o Catarrhal fever in bovine
27
Q

what is hypersplenism?

A
  • Spleen that is OVERACTIVE IN CELL DESTRUCTION
28
Q

Hyperplasia of monocyte/macrophage population (hypersplenism)

A
  • Any splenomegaly cause can stimulate phagocytic population in spleen to proliferate and fill available splenic space
    o Lead to hyperactivity of phagocytes with resultant ANEMIA and/or THROMBOCYTOPENIA
  • *hyperplasia of macrophages can also be caused by infectious agents (ex. Histoplasma, Leishmania)
29
Q

Extramedullary hematopoiesis (EMH)

A
  • in response to increased damage (anemia, infarction) there is proliferation and maturation of normal erythroid and/or myeloid and/or megakaryocytic cell lines in red pulp
  • NORMAL in fetuses and neonates
30
Q

Primary splenic neoplasia examples

A
  • Lymphoproliferative diseases: lymphoma/leukemia
  • Myeloproliferative diseases: histiocytic sarcoma, mastocytosis
  • Hemangioma (VERY RARE!)
  • Hemangiosarcoma
  • Others
    o Fibrosarcoma
    o Fibrohistiocytic nodules, etc.
31
Q

Splenic hemangioma

A
  • Benign tumour of endothelial origin
  • *very RARE
  • Looks similar to splenic hematoma and hemangiosarcoma=*histology is necessary
32
Q

Splenic hemangioma GROSSLY

A
  • Single, soft, dark red nodular mass
  • Histological: well differentiated NORMAL endothelial cells
33
Q

Splenic hemangioma HISTOLOGY

A
  • Composed of cavernous blood-filled spaces lined by well-differentiated endothelium
34
Q

Splenic hemangiosarcoma

A
  • Most common malignant tumour of the canine spleen
  • Malignant tumour of endothelial origin
35
Q

Splenic hemangiosarcoma GROSSLY

A
  • Single to multiple, discrete to coalescing masses
  • Often dark red
  • Spongy, soft
  • +/- metastases
36
Q

Splenic hemangiosarcoma HISTOLOGY

A
  • Blood-filled vascular spaces lined by atypical/dysplastic (ANAPLASTIC) endothelial cells
37
Q

What are possible sequelae to splenic hemangiosarcoma?

A
  • Splenic rupture
  • Hemoabdomen
  • Peritoneal seeding
  • Metastasis
  • Can also develop anemia
  • *often CONCURRENT MASSES in right auricle and liver
38
Q

Secondary (metastatic) neoplasia

A
  • RARE
    o Pancreatic carcinoma
    o Mammary gland carcinoma
  • *functional efficiency of sinusoidal macrophages is thought to PREVENT establishment of metastatic foci
39
Q

If there are splenic nodules with a bloody consistency it may be

A
  • Hematoma
  • Hemangioma
  • Hemangiosarcoma
  • Splenic infarcts
  • Incompletely contracted areas of spleen
40
Q

If there are splenic nodules with a firm consistency it may be

A
  • Nodular hyperplasia
  • Primary neoplasia (lymphoma, histiocytic sarcoma)
  • Metastatic neoplasia
  • Abscess
  • Granuloma
41
Q

Diffuse splenomegaly with a bloody consistency=bloody spleens, it may be

A
  • Septicemia
    o Anthrax, Salmonella
  • Acute hemolytic anemia
  • Splenic torsion
  • Barbiturate euthanasia=artifact (dogs and horses)
42
Q

Diffuse splenomegaly with a firm consistency=meaty spleens, it may

A
  • Septicemia
    o Salmonella
  • Hemolytic disease
  • Lymphoma; leukemia
  • Mast cell neoplasia
  • Histiocytic sarcoma
  • Granulomatous disease
    o Histoplasmosis
  • Amyloidosis
43
Q

Tonsils and mucosa-associated lymphoid tissue (MALT)

A
  • Subject to similar disease processes as the lymph nodes
  • Constantly stimulated
  • *important site of entry for pathogens
  • Ex. tonsillitis and tonsil lymphoma in dogs and cats
44
Q

MALT lymphoma in aged cats and dogs

A
  • Low-grade
  • B-cell origin
  • *thought to arise in a background of chronic inflammation

SYSTEMIC PATHOLOGY - 1 (24 decks)

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