Pathology of the Hematopoietic System, Pt. 2 Flashcards
What is multiple myeloma? What does it tend to cause?
malignant tumor of plasma cell origin arising from the bone marrow
neoplastic (clonal) plasma cells secrete immunoglobin leading to hypergammaglobinemia
What are the 3 specific diagnostic criteria of multiple myeloma?
- neoplastic plasma cells in the bone marrow
- lytic bone lesions seen on radiographs
- presence of clonal immunoglobulin paraproteins in the serum (monoclonal gammopathy) or urine (Bence-Jones protein)
How does multiple myeloma present grossly? Histologically?
GROSS: pale pink to dark red gelatinous masses replace bone marrow, typically with multiple masses
HISTO: sheets of neoplastic plasma cells
What is the anatomy of lymph nodes like? What cells are present at each place?
- outer cortex follicles contain B cells
- inner cortex paracortex contain T cells
- medulla mostly contains B cells and macrophages
What are the 2 major functions of lymph nodes?
- filtration of lymph
- launch immune response
How does lymph flow through a lymph node? In what species is this different?
afferent lymphatics —> subcapsular sinuses —> trabecular sinuses —> medullary sinuses —> efferent lymphatics —> thoracic duct
reverse in pigs - cortex = inner; medulla = outer
What are the 3 major reaction patterns seen in lymph nodes?
- SMALL LN - lymphoid atrophy, LN degeneration, LN hypoplasia
- ENLARGED LN - lymphoid hyperplasia +/- drainage, lymphadenitis, metastatic neoplasia, primary neoplasia (lymphoma)
- DISCOLORATION/PIGMENT
What type of reaction is lymphoid hyperplasia? What does this entail?
immunological reaction = response to some type of antigen
lymph nodes are working to drain the site of local infection or vaccination
Lymphoid hyperplasia:
enlarged follicles causing increased lymphocyte production
Lymphoid hyperplasia, histology:
germinal center is prominent
What 4 bacteria commonly cause suppurative lymphadenitis?
- Streptococcus equi subsp. equi (horse)
- Streptococcus porcinus (pig)
- Corynebacterium pseudotuberculosis (sheep, goats)
- Trueperella pyogenes (cattle, sheep)
What 3 microorganisms cause granulomatous lymphadenitis?
- BACTERIA: Mycobacterium bovis, Mycobacterium avium subsp. paratuberculosis (ruminants); Rhodococcus equi (horse)
- VIRUSES: porcine circovirus 2, feline infectious peritonitis
- FUNGI: Blastomyces dermatitidis, Cryptococcus neoformans, Histoplasma capsulatum
Equine retropharyngeal LN:
- MDx: suppurative lymphadenitis
- etiology: Streptococcus equi subsp. equi
- condition: Strangles
What is bastard strangles?
metastatic strangles where the Streptococcus equi subsp. equi is able to hematogenously migrate to internal organs
(fibrinous deposits on lung)
Ovine LN:
- MDx: caseous lymphadenitis
- etiology: Corynebacterium pseudotuberculosis
- AKA: onion skin
Bovine mesenteric LN:
- MDx: granulomatous lymphadenitis
- etiology: Mycobacterium bovis
What is Rhodococcus equi? What are the 2 most common forms of its disease?
common, facultative intracellular Gram-positive bacterium that typically infects foals 1-6 months
- RESPIRATORY: pyogranulomatous bronchopneumonia
- ENTERIC: ulcerative enterocolitis, caseous/granulomatous lymphadenitis
What primary and metastatic neoplasias are commonly found in the lymph nodes?
PRIMARY: lymphoma, plasma cell tumor, histiocytic neoplasms
METASTATIC: carcinomas, melanomas, mast cell tumors
Metastatic oral melanoma, dog:
pigmented, white tissue expands lymph nodes
What is hemosiderosis?
brownish discoloration observed in lymph nodes draining areas of hemorrhage
What causes anthracosis? When is this a common finding?
carbon particles retained in macrophages, mainly located in the medullary cords, causing the medulla of lymph nodes to appear black
common in bronchial lymph nodes of dogs and humans living in polluted urban areas
Anthracosis, cow:
histopathology necessary to differentiate draining pigment from melanoma
What is the structure of the red pulp of the spleen? What 3 functions does it have?
sinusoids/vascular spaces and splenic cord
- filters blood - removes foreign materials (phagocytosis)
- RBC storage
- hematopoiesis (EMH)
Where in the white pulp is each white blood cell found? What is the overall function of the white pulp?
T CELLS = periarterial lymphatic sheaths (PALS)
B CELLS = lymphoid nodules
MACROPHAGES = marginal zone
- immune response
What are the 2 major reaction patterns seen in the spleen?
- diffuse splenomegaly - bloody vs. meaty
- nodular spleen - bloody vs. meaty
(meaty = cells!)
What are 3 causes of diffuse splenomegaly with a bloody consistency (bloody spleen)?
- congestions - torsion, barbiturate euthanasia
- septicemia - anthrax
- acute hemolytic anemia
Barbiturate-induced splenomegaly, horse:
acute passive congestion
(diffuse, bloody)
Splenomegaly, dog with gastrosplenic torsion/volvulus:
spleen wraps around enlarged stomach
(diffuse, bloody)
Immune-mediated hemolytic anemia splenomegaly, dog:
+ jaundice!
(diffuse, bloody)
Splenomegaly due to anthracosis, cattle:
congestion
(diffuse, bloody)
How does anthrax affect carcasses? How should the presence of anthrax be confirmed postmortem?
carcass will bloat and the animal develops rapid postmortem autolysis causing blood to ooze from body orifices
DON’T perform postmortem examinations - collect postmortem blood sample from a peripheral vein (jugular/ear) and examine a blood smear for the presence of the capsule using M’Fadyean methylene blue stain
How does Bacillus anthracis stain?
METHYLENE BLUE - large bacillus with a characteristic red-stained capsule that forms short chains with square ends
What are the main 5 causes of diffuse splenomegaly with a firm consistency (meaty spleen)?
(firm, filled with cells NOT blood)
- neoplasia
- prolonged septicemia
- chronic hemolytic anemia
- diffuse granulomatous disease
- diffuse follicular hyperplasia
What are 5 common causes of diffuse granulomatous disease? How does this affect the spleen?
- Mycobacterium bovis
- tuberculosis
- Brucella spp.
- Francisella tularensis
- systemic mycoses (histoplasmosis)
meaty spleen
Splenic lymphoma, dog:
white = neoplastic lymphocytes
(diffuse, meaty)
What causes Tularemia? In what animals is it commonly found in?
Francisellla tularensis
wild rodents (rabbit fever) with zoonotic potential to cause systemic disease in cats
How does Tularemia affect the spleen?
multifocal miliary white foci/abscesses (also found in lymph nodes and liver) - diffuse meaty spleen
Diffuse lymphoid hyperplasia, dog:
diffuse, meaty
What are 5 conditions that can cause the spleen to become nodular with a bloody consistency?
- hematoma
- hemangiosarcoma
- incomplete/irregular contraction
- acute splenic infarct (matures into a firm consistency)
- nodular hyperplasia
Splenic hematoma, dog:
focal, dark red nodule - histopathology required to differentiate between hematoma and hemangiosarcoma
(nodular, bloody)
What are hemangiosarcomas? Why is the prognosis so poor?
most common malignant tumor of the canine spleen that forms single to multiple, discrete to coalescing masses that can cause hemoabdomen upon rupture
high chances of metastasis
(nodular, bloody)
What causes classical swine fever? How does it cause disease?
(hog cholera)
- Pestivirus
- targets macrophages, endothelial, and epithelial cells
What is the gross appearance of the kidneys, spleen, tonsils, and cecum/colon of a pig affected by classical swine fever?
KIDNEYS: hemorrhage (turkey-egg kidney)
SPLEEN: splenic infarcts along edges (nodular, bloody)
TONSILS: necrotizing tonsilitis
CECUM/COLON: button ulcers
Classical swine fever; tonsils, cecum/colon, kidney:
(nodular, bloody spleen)
What 4 conditions cause the spleen to become nodular with a firm consistency (meaty)?
- focal nodular hyperplasia
- granuloma (Mycobacterium)
- abscess (Strep. equi subsp. equi, Rhodococcus equi, Corynebacterium)
- neoplasia (lymphoma, histiocytic sarcoma, splenic stromal sarcoma, metastasis)
Nodular hyperplasia, dog:
histopathology needed for differentiation
(nodular, meaty)
Multifocal granulomatous splenitis, turkey:
(nodular, meaty)
What is histiocytic sarcoma? In what dogs is it most commonly found?
neoplasia of interstitial dendritic cell origin (metastatic - poor prognosis)
Bernese mountain dogs, Rottweilers, Golden retrievers, Flat-coated retrievers
What are the 2 forms of histiocytic sarcoma? What organs does it commonly affect?
- localized
- disseminated
(nodular, meaty)
spleen, lungs, meninges, skin, lymph nodes, bone marrow, synovium
Metastatic carcinoma, dog:
(nodular, meaty)
What is another name for siderotic plaques? What are they? How does the spleen appear grossly?
Gamma-Gandy bodies
common incidental finding in older dogs of mineral and hemosiderin accumulation on the spleen
spleen seems rusted
What causes splenic amyloidosis? How does the spleen appear?
chronic inflammation causes macrophages to secrete cytokines, resulting in amyloid fiber deposition
yellow-orange, waxy appearance
Thymus, lamb:
found above the heart, large in newborns and retracts with age
What is the structure and function of the thymus?
composed of epithelial and lymphoid tissues in a lobulated fashion with cortical and medullary areas
proliferation and maturation of T cells
What is the most common cause of thymic hypoplasia? Neoplasia?
- severe combined immunodeficiency (SCID) in Arabian foals (autosomal recessive) and Basset hounds (X-linked)
- thymic lymphoma
- thymoma
What causes severe combined immunodeficiency in Arabian foals? What does this result in?
autosomal recessive defect in DNA-dependent protein kinase (DNA-PKcs)
absence of functional B and T lymphocytes
- severe lymphopenia and hypogammaglobinemia
How does severe combined immunodeficiency develop? What 3 pathogens commonly affect SCID foals?
- clinically normal at birth
- begin to develop disease at 10-35 days of age (diarrhea and pneumonia)
- affected foals die before 5 months of age
- equine adenovirus
- Cryptosporidium parvum
- Pneumocystis carinii
What are 2 common gross findings in severe combined immunodeficiency foals?
- hypoplasia of thymus, lymph nodes, and spleen
- cranioventral bronchoneumonia
How do the 2 primary neoplasias of the thymus compare?
- thymic lymphoma - neoplastic proliferation of T-lymphocytes most common in younger animals (cats, calves, dogs) with malignant behavior
- thymoma - neoplastic proliferation of thymic epithelial cells less common (dogs, sheep, goats) and is slow-growing and encapsulated
Thymoma, goat:
What is the function of tonsils?
serve as the immune system’s first line of defense against ingested or inhaled foreign pathogens and frequently engorge with blood to assist in immune responses
- have M cells on their surface to uptake antigens and present them to T and B cells
What commonly causes lymphoid depletion in tonsils?
viral infections (classical swine fever)
What are the 2 limited causes of tonsil inflammation? Why is it limited to these 2?
primary or hematogenous infections
tonsils do not have afferent lymphatics - nothing is drained
In what dogs are inflammatory polyps common on the tonsils?
older dogs
What is the only type of neoplasia possible in the tonsils? 3 examples?
primary (no afferent lymphatics)
- squamous cell carcinoma
- lymphoma
- malignant melanoma
What is characteristic of classical swine fever in pigs?
multifocal necrosis of palatine tonsils
Tonsillar squamous cell carcinoma, dog:
