Lymphoreticular System Flashcards
The Innate immune system is made up of what cells?
Macrophage, Natural Killer Cell, Dendritic cell, Neutrophil, Eosinophil, Basophil
The Adaptive immune system is made up of what cells?
B cell –> Antibodies
T cell –> CD4+ T cell, CD8+ T cell
What cells overlap between the Adaptive and innate immune system?
T-Cell
Natural Killer T cell
The lymphoreticular system is made up of…
thymus, spleen, LN’s, Mucosa-associated lymphoid tissue (MALT), tonsils, bone marrow
What cells are present within the outer cortex of the thymus?
Immature T-cells migrate to thymus for proliferation & maturation
What cells are present within the inner medulla of the thymus?
Defective mature T-cells move to blood
What age of life is the thymus important in the lymphoreticular system?
Foetal life
The thymus is associated w/ what type of immunity and lymphocytes?
Cell-mediated immunity
Production of helper (Th 1&2) and T-regulatory lymphocytes
What pathologies affect the thymus?
Thymic mass (thymic lymphoma, thymoma, other epithelial tumours)
Benign thymic hyperplasia
Cyst
haemorrhage - acute
thymic atrophy
What clinical signs may be present if there is a thymus pathology?
Resp signs due to pleural effusion
Myasthenia gravis (canine thymoma)
Hypercalcemia & assoc’d signs (lethargy, PU/PD)
How would you approach thymus pathologies diagnostically?
Good clin Hx, Physical exam
General blood panel (hematology, biochemistry, urinalysis)
Imaging (chest rads, chest ultrasound, thx CT)
Sampling (cytology, Bx)
Lymphomas can arise in the thymus through
malignant transformation of lymphocytes
Thymomas arise from…
neoplastic epithelium
Describe thymomas on cytology
Monomorphic population of small lymphocytes or mixed lymphoid cell population
Small amt of mast cells interspersed among lymphocytes
What cells are not typically seen with lymphoma?
Mast cells & melanocytes
Why is it difficult to distinguish between thymoma and LSA on FNA?
Thymic epithelial cells do not readily exfoliate & rare to see on FNA
How should you differentiate from Thymoma and LSA?
PARR - PCR for antigen receptor rearrangements
Flow cytometry
Histopath +/- Immunohistochem
Describe the structure of the spleen.
Capsule - subject to action of the ANS
Red Pulp - RBC component
White Pulp - immune regulation
Describe the functions of the spleen.
- Assoc’d w/ humoral-mediated immunity –> production of B-lymphocytes & antibodies
- macrophages filter blood for removal of infectious agents
- Removal of old/abnormal RBC’s w/ inclusions or coated w/ antibody & complement
- Storage of RBCs, platelets, Fe
- Extramedullary haematopoiesis (EMH) in presence of anemia
What vascular pathology(ies) might occur?
Thrombus
What inflammatory/infection splenic pathologies might occur?
- splenitis
- splenic abscess
- splenic granuloma
What traumatic splenic pathologies may occur?
- Haematoma
- Splenic torsion
What anomaly in the spleen may occur?
Splenic cyst
What metabolic pathologies can occur in the spleen?
Splenic congestion
Due to CHF, PSS, Drugs, Portal hypertension
Are there any idiopathic pathologies of the spleen?
No
What neoplastic pathologies of the spleen can occur?
- Hematopoietic tumors
- sarcoma (HSA)
- metastasis
What degenerative pathologies of the spleen may occur?
- Myelolipomas
- Nodular lymphocytic hyperplasia
What are some things you might look for on a physical exam for splenic pathologies?
- Abdominal effusion
- VPCs
- Pain
What are you looking for on abdominal palpation that may indicate a splenic pathology?
- Splenomegaly
- Altered shape, irregular margins
- altered consistency
What is the general location of the spleen?
Located Left cranial abdomen and is associated with greater curvature of the stomach
What is the normal shape of the spleen?
Smooth outer capsule, soft parenchyma
When would a spleen cause regenerative anemia?
Splenic rupture or hemoabdomen
What might you see on blood smear if there is a pathology in the spleen?
Schistocytes
Coagulopathies are seen on bloods and are related to the spleen when what pathologies may be occurring?
DIC
Hypercoagulopathic State
What imaging might you use for looking at the spleen?
Rads, Ultrasound, CT
When might you do splenic aspirates under ultrasound?
Hyperechoic nodules &/or mixed echogenicity
How might you take a biopsy of the spleen?
Surgical of laparoscopic excisional biopsy (+/- impression smear from sample)
What additional tests might be used to diagnose splenic pathologies?
- PARR, immuncytochemistry
- +/- culture & susceptibility if suspect cystic lesion or abscess
What is the most common canine splenic neoplasm?
Splenic hemangiosarcoma
What canine breeds are predisposed to canine splenic HSAs?
GSD
Golden retrievers
Canine Splenic HSAs are associated with…
- Coagulopathies (DIC)
- Arrhythmias (VPCs)
- Sudden collapse due to rupture - hemoabdomen
- Concurrent RHS atrial mass tumor
What essential pre-operative stabilisation must occur if there is a canine splenic HSA?
if hemoabdomen is present, give fluids &/or transfusions
Can you determine HSA being benign or malignant on ultrasound appearance ?
No
Describe the structure and function of lymph nodes
- Outer cortex - Lymphoid follicles; inner germinal centre is the site for B-cell proliferation; outer edge has more T-cells
- Inner medulla - cords of lymphocytes, macrophages, plasma cells; has activated B-cells
What peripheral LN’s are important to know and feel on physical exam?
- Submandibular
- Prescapular
- Popliteal
- Inguinal & axillary (if enlarged)
What are you looking for when asking about Hx or doing a physical exam?
- Travel Hx
- Concurrent systemic clinical signs
- painful around area
- recent trauma, Sx, bite, wound
- other lesions?
- signle or multiple LN’s involved?
- Measure & record LN size/consistency
Lymphadenopathy can be…
Non-neoplastic or neoplastic
What are forms of non-neoplastic lymphadenopathy?
- Lymphoid Hyperplasia
- Inflammation - Lymphadenitis
What neoplastic lymphadenopathies may occur?
- Primary - Lymphoma
- Secondary - Metastatic Dz
Compare and contrast FNA and Excisional/Tru-cut Bx
FNA
* Easy to perform, quick, conscious or sedated, eval cell morphology, may not be representative, low cellularity & higher risk blood contamination, less complications, cheap
Bx
* Req’s experience, GA/deep sedation, eval morpholgoy & structure, larger tissue sample, infection, wound dehiscence, peripheral oedema, more costly
Lymphoid hyperplasia is what kind of process?
Reactive
If you did an FNA on a lymph node with hyperplasia, what might you see?
Predominantly small cell lymphocytes
<20% med to large lymphocytes
Plasma cells 5-20%
If you did an FNA on a patient with lymphadenitis, what might you see?
- 90% well-differentiated small cell lymphocytes
- Up to 10% med to large lymphocytes
- Occasional plasma cells, histiocytes, neutrophils, mast cells
What is the main differential for lymphoma?
Generalised lymphadenopathy
High-grade LSA will look like what on cytology?
> 50% med to large lymphocytes
What are the 2 main types of lymphoma?
Diffuse large B-cell LSA
Small cell T-zone lymphoma
What tests are required to differentiate between lymphoid hyperplasia and low-grade LSA?
- Histopath (excisional vs incisional wedge Bx/Tru-cut)
- immunophenotyping (immunocyto- or histochem)
- PARR
- flow cytometry (expression of specific cell markers)
