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(Bone marrow, Thymus, MALT-Mucosa-associated lymphoid tissue), spleen,…

- - - - bone marrow replacement with fibrous connective tissue
      - bone marrow hypoplasia/aplasia and resultant panleukopaenia
  - - - increase in haematopoietic precursor cells as a response to an increased peripheral demand or due to hypofunction of blood cells
      - Megakaryotic hyperplasia- response to decreased platelets
      - Erythroid hyperplasia- response to anaemia, haemorrhage
      - Lymphocytosis- epinephrine-associated, viral infections, antigenic stimulation
      - Myeloid hyperplasia (specifically granulocytic cell lines) Neutrophilia- bacterial infections, tissue necrosis
        Eosinophilia- parasites, hypersensitivities
  - - - Circulating blood- leukemic cells infiltrate blood
      - Lymphoid tissues= lymphoma
      - Bone marrow= leukemia
        
        Bone marrow hypercellularity- crowd out normal cells= myelophthisis
        
        Leads to anaemia/thrombocytopaenia/neutropaenia
        
        Leukaemic cells- may be seen in peripheral blood and can infiltrate the spleen and liver- increase in size
        
        neoplasia of blood precursor cells in bone marrow, detected on basis of complete blood counts (high white cell count) and blood smear- oddly shaped
        
        Myeloid leukemia- neoplasia of precursor non-lymphoid leukocytes, erythrocytes and megakaryocytes- arises in bone marrow
        
        Lymphoid leukaemia- neoplasia of lymphoid precursors
      - Myelophthisis
        
        Normal bone replaced with
        
        Fibrous connective (scar) tissue- myelofibrosis
        
        Neoplastic tissue- leukemia
        
        Result in pancytopenia (blood) due to competition for space and nutrients
        
        Replacement of normal hematopoietic tissue within the none marrow by abnormal tissue
  - - - Often associated with cachexia- wild antelope
      - haematopoietic precursor- scarce
      - Due to starvation = catabolism of fat and the bone marrow reticular cells produce a mucoid ground substance
- - - - Lymphoma- bilateral tonsillar enlargement
    - - tonsillitis
- - - - ASF
      - anthrax
      - Salmonellosis
    - - Haemangiosarcoma- malignant neoplasm of vascular endothelial cells
    - - Gastric dilatation volvulus
        
        Due to splenic torsion around the gastrosplenic ligament with the stomach
      - Barbiturate euthanasia - realaxtion of smooth muscle in capsule- pooling of blood
      - Splenic torsion
        
        Common in dogs and pigs
        
        occludes veins- congestion and there might be an occlusion of arteries- ischaemic necrosis
      - Shock
      - sedation
    - - Primary- trauma
      - Secondary- thinning of capsule in splenomegaly, splenic neoplasa etc
  - - - Amyloidosis (rare)
        
        swollen, pale, hard firm brittle
    - - Extra-medullary haematopoiesis
      - Diffuse primary neoplasm
        
        Splenic lymphoma
        
        Mast cell tumour
      - Inflammation
        
        splenitis
        
        cyrptococcus, blastomycosis, histoplasmosis, aspergillus
      - Diffuse metastatic/secondary neoplasm
        
        Splenic lymphoma
        
        leukemia
      - Hyperplasia
        
        Red pulp hyperplasia
        
        macrophage proliferation- extensive phagocytosis and removal of debris
        
        IMHA- immune mediated heamolytic anaemia
        
        White pulp hyperplasia
        
        diffuse lymphoid hyperplasia- antigenic stimulation
        
        Heartwater (Ehrlichia ruminatium) Equine herpesvirus 1 in foals, malignant catarrhal fever
      - Abscessation
        
        uncommon
        
        bacterial causes- Trueperella pyogenes
  - - - Agonal change- immediately before death- terminal circulatory failure
      - multifocal incompletely contracted areas of the spleen- paler areas with wrinkled capsule
    - - haemangioma- benign neoplasm of vascular endothelium- rare, usually solitary masses covered by thin shiny serosa
      - haemangiosarcoma- most common primary and secondary MALIGNANT neoplasm of spleen - single to mulitple discrete to coaslescing dark red masses, often rupture- haemoperitoneum and hypovolaemic shock
    - - Benign nodular hyperplasia
        
        abnormal blood flow through the nodule
      - splenic vascular neoplasms
      - Trauma induced
        
        Rupture of blood vessels
    - - any time you put extra cells in spleen you run the risk of infarction
      - edges of spleen
      - End-artery system
      - Acute are slightly more wet with chronic being paler, sunken, firmer- necrotic
      - discrete raised dark red- haemorrhagic infarcts
        discrete raised and pale if arterial occlusion
      - Causes: vascular endothelial damage, hypercoagulable states septic emboli
- - - - Sporadic Bovine leukosis SBL
        
        Young animals- cause unknown
        
        3 basic forms
        
        Calf/multicentric form
        3-6months
        Rapidly progressive
        symmetrical lymph node enlargement
        may involve other organs
        
        Juvenile/thymic form
        6-30 month old beef cattle
        Respiratory distress and weight loss
        large cranial thoracic and lower cervical masses- massive thymus
        
        Skin form- rare
      - EBL=enzootic bovine leukosis
        
        Bovine leukeamia virus (BLV) - oncogenic virus - not all infected cattle get lymphoma
        
        Multicentric lymphoma
        
        Dairy cattle
        
        Commonly infected sites
        
        Uterus
        
        thickened white-creamy wall, watery fluids- uterine lumen
        infertility
        
        Spinal canal
        
        Pinkish pale cream coloured tissue
        Posterior paresis and paralysis pressure of extradural mass on cauda equina or lumbar spinal cord
        
        Abomasum
        
        Abomasal folds - thickened, often multi nodular and cream coloured, associated ulceration
        Sudden death- rupture of ulcers
        anorexia
        Dysphagia
        vagal indigestion
        constipation or diarrhoea
        abomasal tympany
        hypomotility
        
        Heart
        
        wall thickened creamy in colour
        arrhythmias
        jugular distension
        tachycardia
        murmurs
        congestive heart failure
    - - Tan white to pinkish nodules
      - thickening of walls of tubular organs
      - Organomegaly
      - Lympohoid tissue is not vascular so unlikely to be red or black in colour
      - Soft because don't have prominent fibrous vascular tissue
    - - Peripheral lymph node involvement
      - Multicentric lymphoma common
      - Middle aged to older dogs
      - Most common canine haematopoietic tumour
      - Spleen, liver ,lymph nodes
    - - Extranodal sites- nose, kidney, CNS
      - Thymic and multicentric- young cats with FeLV
      - Alimentary most common
      - Most common malignant tumour of cats
      - No peripheral lymph node involvement
    - - Not as common
      - Anatomical subtypes
        
        Multicentric (most common)
        Abdominal and thoracic cavities
        Weight loss and ventral oedema
        
        cutaneous and subcutaneous
        
        Alimentary/GIT (proximal small intestine)
        Wasting syndrome
        Malabsorption from small intestine
        
        Abdominal (multiple oragns) - liver
        
        , spleen, visceral lymph nodes
  - - - swollen lymph node with a pus filled centre
      - fistulate to skin surface
      - Response to pyogenic bacteria in node
      - strangles Streptococcus equi equi- upper airway and lymph nodes of head and neck
    - - High contagious
      - Infection drains to regional lymph nodes- superficial nodes are more often affect then internal/ visceral nodes
      - Corynebacterium pseudotuberculosis
      - thick wall- firbous connective tissue capsule - filled with thick necrotic cheese lik elumpy pus like material (can be gritty-dystrophic mineralization)
      - Can involve internal visceral lymph nodes and organs
      - laminated appearance- chronic
    - - Bovine tuberculosis
      - Intracellular bacterium: Mycobacterium bovis
        
        Enlargement of lymph nodes- single to multiple discrete- whitish cream coloured to yellow tan gritty nodules
      - Gritty- dystrophic calcification/mineralization
      - disseminate to viscera and organs
  - - - Epithelial cells- not normally there
      - mast cells- in clusters not normal
      - melanocytes- in malignant melanoma