Pathology Of The Lymphoreticular System Flashcards
(81 cards)
What organs are in the Lymphoreticular System? (Name the primary and secondary organs)
Primary: Bone marrow and Thymus (in thorax)
Secondary: Lymph nodes, Spleen and MALT
Name the common pathology causes to this system.
- Infection
- Immune-mediated disease
- Neoplasia
Diseases of the Thymus:
What can cause Thymic hypoplasia?
- Developmental abnormalities (associated with primary immunodeficiency) Eg. x-linked SCID
- Systemic viral lymphoid depletion Eg. FeLV, FIV, CDV
this infects the lymphocytes (T cells)
Diseases of the Thymus:
What happens in Feline Thymic lymphoma?
Name the CS, DDx, Tx
- Malignant - infected lymphocytes and thymus reacts
- Usually associated with FeLV - CATS
- Cs:
-Anorexia, Wt loss, dyspnoea (caused by sto mass)
(cats cope well by resting - don’t see breathing issues -discover disease late) - DDx:
-Thoracic rads show soft tissue opacity mass
-Effusion - cytology of pleural fluid, Fine needle aspiration biopsy (FNAB)
(Affects mediastinal LN possible) - Tx:
-Chemotherapy
Diseases of the Thymus:
What is a thymoma?
Name the Cs, DDx, Tx
- Benign - neoplasia of thymic epithelial cells - DOGS
- DOGS - breed disposition - GSDs + Labs
- CS
- Dyspnoea, Dysphagia - space occupying lesion in anterior thorax
- thoracic effusion
- Paraneoplastic sydromes:
a) hypercalcemia (release of PTHrp from tumour cells: ↑bone resorption + distal tubule Ca reabsorption
b) Myasthenia gravis with megaoesophagus - REGURG (autoimmune - muscle weakness) - DDx: Thoracic rads, u/s, cytology of fluid/FNAB
- Tx: Surgical excision of tumour +/- chemo
Good prognosis for Stage 1 Thymoma - no spread from thymic capsule and no paraneoplastic disease
Diseases of Lymph Nodes:
What is the function of
a) Lymphocytes
b) Lymph Nodes
a) Lymphocytes constantly move around body in blood- visiting secondary Lymphoid organs - searching for foreign antigen and APCs
IN: High Endothelial Venules
OUT: Efferent Lymphatic vessels + thoracic duct
(back to blood)
b) Lymph Nodes trap foreign material (prevent systemic spread) and optimise exposure of lymphocytes to Antigen
Best environment for Lymphocytes to activate, proliferate, differentiate (Effector T cells + AB from plasma cells)
-also antigen presentation - interdigitating Dendritic cells to Tcells and follicular DC to B cells
Diseases of the Lymph nodes:
a) Define Lymphadenopathy and name the two types:
b) Common causes of Lymphadenopathy?
a)
1. Localised (regional disease)
2. Generalised (systemic disease- check spread to spleen
b) Infection (↑WBC count with pyrexia) and neoplasia
Diseases of the Lymph nodes:
Name the DDx of generalised lymphadenopathy:
1) Haematology
- Lymphopenia - viral infection ↓L
- Neutropenia + left shift - Bac infection - ↑N
- Eosinophilia - Parasite or allergy - ↑E
2) Lymph node Biopsy: Fine needle, Core, Excisional
Chylothorax:
a) What are the causes of C?
b) What are the CS?
c) What is the definitive DDx?
a) Thoracic duct is damaged/perforated, eroded by a tumour usually causing the efferent lymph to leak out into thoracic cavity
b) Compromised resp function, disrupt lymphocyte migratory function
c) Milky, pink liquid appearance tapped from thorax, lymphopenia
What happens when malignant cells attempt to metastasise via lymphatic system?
-They get stuck in the LNs, trapped - establishing 2° site of tumour formation
Eg. MCT, Malignant melanoma, SCC
- blocked lymphatics can cause peripheral oedema (limbs)
Name the Differential DDx based on histopathology:
- Reactive LN
- Lymphadenitis
- 1° Neoplasia
- 2° Neoplasia (mets)
Describe the histopath appearance of
a) Reactive LN
a) Reactive LN
- Normal architecture with increased cellularity -cloned- reacting to antigenic challenge - therefore enlarged
- 2° follicles with germinal centres
Describe the histopath appearance of
b) Lymphadenitis -
Name the 3 subcategories with appearance and examples
b) Lymphadenitis
- Active infection WITHIN LN - LN trapped antigens but causing disease inside
- Appearance = similar to reactive LN, but with pyogranulomatous inflamm
-3 subcategories
1. Suppurative - yellow green pus, liquid abscess
Eg. Strept equi - Strangles
- Caseous - cottage cheese abscess
-alternate layers of fibrosis and necrosis and abscesses can burst expelling infectious pus
Eg. Corynebacterium pseudotuberculosis (sheep/goats) - Granulomatous - inflamm response
Eg. Mycobacterial infection = TB/Johnes disease
Describe the histopath appearance of
c) 1° Neoplasia
(another name?)
d) 2° Neoplasia (mets)
c)
- Lymphoma
- Non-infectious
- Lack of normal architecture (large no of nucleated cells)
- Large no of abnormal lymphocytes (large) with ↑ mitotic figures
d)
- Metastasis
- Areas of normal lymphoid tissue with infiltration of neoplastic cells either focal or diffuse
Haem route goes to Liver/Lung but Lymphatic route to nearest LN
Eg. MCT, ST sarcoma, tonsillar squamous cell carcinoma, Metastatic melanoma
Diseases of the Spleen:
Name potential diseases that can occur to the spleen:
- Trauma/Rupture/haematoma (eg RTA)
- Torsion with GDV
- Infarction (Eg classical swine fever)
- Splenomegaly - diffuse, nodular
Splenomegaly
Explain the difference of diffuse and nodular S and name examples of each one
-Diffuse S is enlargement of the spleen generally whereas only nodules of the spleen are enlarged in Nodular S - found at Clinical Exam
- Diffuse S:
- Venous congestion (eg following torsion and also PM artefact after barbiturate)
- Lymphoid hyperplasia (systemic infectious/inflamm/immune-mediated)
- Systemic amyloidosis
- Neoplasia (lymphocytes, multiple myeloma) - Nodular S:
-Nodular hyperplasia - benign
- Abscess/cyst (infectious agent)
Diff to tell apart from N hyperplasia
- 1° Neoplasia - Lymphoma, Haemangioma, Haemangiosarcoma
-2° Neoplasia - Metastatic disease (eg. MCT)
What infectious agents particularly impact the Lymphoreticular system?
a) Viruses
b) Bacteria
c) Protozoa
a) Malignant Catarrhal Fever (herpes virus) Classical Swine Fever FeLV/FIV/Canine distemper/FIP Equine Infectious Anaemia
b)
Bacillus anthracis (Anthrax)
- haemorrhage from orifices, sudden death
Mycobacterium bovis (TB)/ M. avium paratuberculosis (Johnes disease)
Corynebacterium pseudotuberculosis
-not curable
c) Exotic - Leishmania, Babesia, Ehrlichia, Theileria
Splenic disorders:
1a) Name the 3 important branches of the Splenic A + V?
1b) What do you have to be careful when exteriorising the Spleen in relation to vessels?
1a) Left limb to pancreas, greater curvature of the stomach (gastroepiploic), fundus of the stomach (short gastrics)
1b) Must ligate the main S artery in removal - stop haemorrhage
Must lift the omentum covering the S A + V to see the branch to Pancreas - ligate after branching or P will die
Splenic disorders:
2a) Name the functions of the spleen:
2b) Name the parts of the spleen that makes up the Red pulp and the White pulp
2c) Is it vital?
2a)
Red pulp-
-RBC maintenance (filters), iron metabolism (stores iron from past RBC)
-Blood reservoir - smooth muscle capsule contracts for blood boost
-Haematopoiesis (helps out Bone marrow)
White pulp-
-Immune functions - protects from septicaemia
2b) Red pulp is the venous sinuses and the white pulp is lymphoid tissue
2c) Dogs and cats can survive normally without a spleen - don’t live longer enough to see effects
Splenic disorders:
3) Which is performed more commonly, Total Splenectomy or Partial and why?
- Total Splenectomy is more common - much easier to remove whole spleen and indicated for cases in neoplasia or trauma
(Check for mets is suspect malignant neoplasia)
Splenic disorders:
4) Describe the procedure of Total splenectomy:
1) Large ventral midline abdominal incision
2) Locate spleen in left abdomen and the tail section
3) Double ligate and transect the hilar vessels (can be in bunches) - until main a + v reached
4) Locate the S a + v - artery is white whereas the vein is wider, thinner, darker (see blood)
5) Separate with haemostats and ligate them separately with ligatures closer to the side staying in body
6) Carry on ligating until short gastric vessels - preserve
7) Transect the gastrosplenic ligament
8) Take out - send off for histopath, give as much for DDX but clots common
Splenic disorders:
5) a) Describe the method of fast total splenectomy
b) Describe the limitations to this surgery
a)
1) Start at tail of spleen
2) Ligate in 3 places - short gastric vessels, left gastroepiploic a + v and splenic a + v distal to pancreas branch
b) Difficult if anatomy distorted by major trauma, ligate wrong vessels
Splenic disorders:
6) Describe indications for partial splenectomy
- Used in cases of accidental lacerations
- Focal and benign disease eg. trauma
1) Ligate hilar vessels and transect ones to the diseased spleen - forming a line of demarcation
2) Place forceps and remove diseased portion
3) place two rows of continuous mattress suturing and then one close to cut end of spleen
4) Use stapling device eg. linear stapler
- Difficult to do because because spleen friable/soft
Splenic disorders:
7a) What are the perioperative considerations for this surgery?
7b) What are the intraoperative considerations?
- Increased risk of cardiac arrhythmias with splenic masses - monitor ECG during surgery/ anti-arrhythmias
- DIC can occur with neoplasia - perform coagulation tests
- Examine whole abdomen for mets
- Check Blood pressure
b) -Will need: Abdominal retractors Lot of swabs (have radio-opaque + remember to count) Suction (measure blood and weigh swabs) Waterproof drapes
- Haemorrhage main concern - deal with hypovolaemic shock - slipped ligatures so can use vascular clips/vessel sealants
- if GDV predisposed - gastropexy
- Gastritis/ pancreatitis