L3: Path of Lymphoid System (Castleman) Flashcards
1ary lymphoid tissue**
Thymus (produces T cells)
Bone marrow (primates, rodents)
Peyer’s Patches (ruminants, pigs, horses)
Bursa of Fabricious (birds)
2ary lymphoid tissue**
LN
Spleen
MALT (including GALT, BALT, tonsils)
medullary chords primarily made up of:
B cells
3 main causes of LN enlargement
1) lymphadenitis (infectious, immune, toxic etiology)
2) Neoplasia (primary, metastatic)
3) Lymphoid hyperplasia (Ag driven)
types of exudate involved in lymphadenitis
suppurative
hemorrhagic
necrotizing
granulomatous (often w/ fungal or mycobacterial dz)
2 types of lymphoid hyperplasia
paracortical
follicular
causes of lymphoid hyperplasia
- Ag stimulation
- viral infection (ie. Malignant catarrhal fever, bovine leukemia, FIV
main cause of LN hypoplasia
Primary immunodeficiency (ie. Combined Immunodeficiency (CID) in Arab foals, X-linked CID in dogs)
what breeds susceptible to X-linked CID?
basset
Jack russel
Welsh corgi
CID pathogenesis
genetic defect in DNA-dependent protein kinase, defective DNA repair
Causes of LN Atrophy
1) viruses that replicate in lymphocytes and induce apoptosis/necrosis (distemper, parvo)
2) glucocorticoids (endogenous, exogenous)
3) chemotherapeutic drugs, radiation, malnutrition, cachexia (wasting)
Fx of spleen RED PULP
- RBC storage
- Ag removal
- hematopoiesis/erythropoiesis
- RBC destruction
Fx of spleen WHITE PULP
- acquired immunity (B/T cell responses)
- T cells in periarteriolar lymphoid sheaths*
- B cells in follicles*
What can cause DEC. spleen size? (UNCOMMON)
- immunodef.
- senile atrophy
- wasting/cachexia
- lymphoid necrosis alone will NOT cause dec. size!!
What can cause INC. spleen size? (COMMON)
- uniform splenomegaly
- splenic nodule/masses
uniform splenomegaly and bloody when cut indicates:
- congestion
- torsion
uniform splenomegaly WITHOUT blood when cut indicates:
- septicemia
- granulomatous spenitis
- anemia
- lymphoma
- extramedullary hematopoiesis
- amyloidosis, storage disease
BLOODY Splenic nodules/masses differentials:***
- hematoma
- hemangioma/hemangiosarcoma
- nodular hyperplasia w/ hyperemia
- splenic infarct
- incomplete splenic contraction
FIRM/NON-BLOODY Splenic nodules/masses differentials:***
- nodular hyperplasia
- granulomatous splenitis, splenic abscess
- lymphoma
- metastatic neoplasm
common sites of hemangiosarcoma in dogs
- spleen
- LIV
- R atrium
- LU
what is contained within nodular hyperplasia?
abundant lymphoid tissue w/ large amts. of lymphocytes and macs
siderotic plaques
- Fe and Ca deposition in nodules on spleen
- gray/tan color
- usually in older dogs
Structure/Fx of thymus
- 1ary lymphoid organ for T cell development and maturation
- has cortex and medulla
what lies in cortex of thymus?
primitive and maturing lymphocytes
what lies in medulla of thymus?
- thymic epithelial cells and Hassal’s corpuscles
- myoid cells
- interdigitating/dendritic cells
- lymphocytes
diseases associated with a small thymus***
- thymic hypoplasia (ie. CID)
- maturation and aging (involution)
- thymitis (ie. salmon poisoning in dogs)
- thymic atrophy (lymphocyte apoptosis/necrosis) <–most common
Causes of thymic atrophy**
1) viral diseases: FeLV, FIV, canine distemper, equine herpesvirus 1, feline panleukopenia, parvo
2) steroids
3) nutritional deficiency (starvation, zinc def., protein def.)
4) toxins (lead, mercury, polychlorinated biphenyls)
diseases assoc. with large thymus***
1) thymic hemorrhage (young dogs)
2) lymphoma
3) thymoma
what does thymoma look like histologically?
large # lymphocytes
Q: all result in decreased thymus size EXCEPT:
a) parvo
b) lymphoma
c) steroids
d) canine distemper
e) A and D
b) lymphoma
Q: uniformly enlarged dog spleen that bleeds on cut surface is most likely:
a) hemangiosarcoma
b) hemangioma
c) lymphoma
d) congestion
e) nodular hyperplasia
d) congestion
Q: irregular dark red nodule in a spleen that bleeds on cut surface could be all EXCEPT:
a) hemangiosarcoma
b) hemangioma
c) granulomatous splenitis
d) hematoma
e) nodular hyperplasia
C) granulomatous splenitis (will be DIFFERENT correct answer on exam!!)
lymphoproliferative disease
all neoplasms arising from lymphocytes
lymphoma
- malignant neoplasm of lymphocytes
- infiltrates and destroys lymphoid tissue and other tissues
leukemia def.
neoplasm of lymphocytes or hematopoietic cells arising from the bone marrow
2 patterns of lymphoma
diffuse or follicular
anatomic classifications of lymphoma
multicentric thymic alimentary cutaneous solitary
cytologic classification of lymphoma
well differentiated to lymphoblastic
most common form of lymphomas in dogs
B-cell lymphomas
-associated with gamma herpesvirus
most to least common distribution types of lymphoma in DOGS**
1) multicentric (generalized, liver, spleen, kidneys, heart, bone marrow, CNS)
2) alimentary (intestine, mesenteric LN, less commonly LIV/SP)
3) thymic (thymus, cranial mediastinum. Assoc. with hypercalcemia)
4) cutaneous
5) solitary or specialized (brain, lung, lymphomatoid granulomatosis)
hypercalcemia is assoc. with what distribution of lymphoma in dogs
thymic
lymphoid infiltrate to liver can –>
icterus
pale areas seen grossly on spleen can be
lymphoid infiltrates (sign of lymphoma)
most common neoplasm in cats**
lymphoma!
FeLV closely associated with what neoplasm in cats?
lymphoma. (>50% 5yrs old or less)
most to least common distribution of lymphoma in CATS**
1) alimentary (jejunum, ileum, mesenteric LN, liver, kidneys)
2) thymic (thymus, cranial mediastinal LN)
3) multicentric (generalized LN, liver/spleen, CNS)
4) solitary (kidneys)
which distributions of lymphoma in cats more associated with being FeLV positive?
Thymic
Multicentric
which distribution of lymphoma in cats often assocc. with pleural effusion and compressive atelectasis?
thymic
which distribution of lymphoma in cats assoc. with obstructive GI disease?
alimentary
pyogranulomatous dz in cats can result in enlargement of kidneys
:)
FIP –> pyogranulomatous vasculitis
:)
most common forms of lymphoma in cattle caused by:
Bovine Leukemia virus (BLV)
-30% have persistent lymphocytosis
most to least common distributions of lymphoma in CATTLE**
1) multicentric (LN, R atrium, abomasum, KID, uterus, spinal epidural fat, intestine, liver, spleen)
2) cutaneous
3) thymic (thymus, bone marrow)
4) calf form (general LN, bone marrow, blood, LIV, SP, +/-thymus, heart, kidneys, uterus)
5) alimentary form
6) solitary (spinal canal)
thymic form of lymphoma occurs in what age cattle
adolescents (6-30mo)
calf form of lymphoma occurs in what age cattle
<6mo
most to least common distributions of lymphoma in HORSES**
1) multicentric
2) others: alimentary, thymic, cutaneous, solitary
Most common anatomic form of lymphoma in cats is:***
alimentary
most common anatomic form of lymphoma in dogs is:***
solitary
R atrial lymphoma is most commonly found in:***
cattle
viral agents have been assoc. with lymphoma in what species***
cattle, cat, dog
review diagram slide 2
:)
