د.سناريا

• Bone Marrow Hypoplasia/ Aplasia


  Decreased proliferative activity, can be in one cell line (e.g. erythrocytic aplasia=aplastic anemia) OR multiple cell lines (e.g. aplastic pancytopenia)
• Main causes of bone marrow hypoplasia

  • Bone marrow suppression
  • Lack of nutrients
  • Endocrine dysfunction
  • Bone marrow degeneration/necrosis
• Bone Marrow Hyperplasia

  Proliferation (hyperplasia) of hematopoietic cells in response to increased peripheral demand or hypofunction of blood cells
• Types of bone marrow hyperplasia

  • Erythroid hyperplasia
  • Megakaryocytic hyperplasia
  • Myeloid hyperplasia
• The term atrophy (decrease in cell size) is seldom used to describe bone marrow
• Serous atrophy of fat

  Gelatinous transformation of fat within the marrow due to catabolism of fat associated with starvation from malnutrition or chronic disease
• Hematopoietic tumors are broadly divided into

  • Lymphoproliferative disease
  • Myeloproliferative disease
• Primary Hematopoietic Neoplasia


  • Lymphoma
  • Lymphoid leukemia
  • Plasma cell tumors
  • Myeloid leukemia
  • Myelodysplastic syndrome
  • Histiocytic neoplasia
  • Mast cell tumors
• Lymphoma


  One of the most common malignant neoplasms in domestic animals, can be sporadic, hereditary or viral in cause
• Classification systems for lymphoma

  • Anatomical site
  • Cellular Morphology
  • Immunophenotype
  • Biologic Behavior
  • Histologic Pattern
• Most of the cells in this lymph node aspirate are medium and large lymphocytes, confirming a diagnosis of diffuse large cell lymphoma
• Clinical Signs of Lymphoma

  • Painless enlargement (lymphadenopathy) of one to multiple lymph nodes
  • Multitude of additional signs dependent upon the organ system involved
• Monocyte-Macrophage System (MMS)


  Bone marrow origin, includes blood monocytes and monocytes that have migrated and differentiated into fixed macrophages in connective tissue throughout the body and within vascular beds of specific organs
• Lymph nodes


  Oval to bean shaped organs distributed throughout the body along lymphatic vessels, help coordinate and direct the body's immune response
• Lymph node structure


  • Outer cortex (follicular structures, B lymphocytes, macrophages, dendritic cells)
  • Inner cortex (paracortical region, T lymphocytes)
  • Medulla (medullary cords, medullary sinuses)
• Conditions affecting lymph nodes

  • Enlarged Lymph Nodes: Lymphadenitis, Lymphoid Hyperplasia, Hyperplasia of monocyte/macrophage system, Primary neoplasia, Metastatic neoplasia
  • Small Lymph Nodes: Lymphoid atrophy, Lymph node degeneration, Lymph node hypoplasia
• Hemosiderosis/ hemosiderin deposition


  Normally a small amount of hemosiderin (storage form of iron) is present within macrophages in the spleen, increased deposition suggests increased erythrocyte destruction/ decreased erythrocyte half-life
• Splenic Amyloidosis


  Most common form is "secondary amyloidosis", associated with deposition of amyloid protein AA secondary to chronic inflammation
• Splenic Rupture


  Most often seen in dogs and cats, can be primary due to trauma or secondary to splenomegaly or splenic neoplasia
• Accessory spleens


  Small red nodules within the omentum, identical to normal spleen
• Circulatory disturbances of the spleen

  • Active hyperemia
  • Passive congestion
• Splenic neoplasia


  e.g. hemangiosarcoma, lymphoma which cause thinning of the capsule
• Result of splenic neoplasia


  Death by exsanguination or healing by scarring
• Accessory spleens ('splenosis')


  Seeding of splenic explants on peritoneal/serosal surfaces following rupture
• Accessory spleens


  • One or more small red nodules within the omentum (looks similar to hemangiosarcoma implants/metastases)
  • Microscopic findings identical to normal spleen
• Active hyperemia


  Seen with acute systemic infection and bacterial sepsis
• Passive congestion


  Caused by disturbances in systemic and portal circulation; can be seen with shock (vascular pooling), barbiturate administration (especially horses, dogs), and hemolytic anemia
• Gross findings of passive congestion

  • Spleen is enlarged/swollen and red-purple to black because of increased amounts of blood (unoxygenated) and oozes blood on cut surface
• Microscopic findings of passive congestion

  • Vascular spaces are dilated and contain erythrocytes. The germinal centers are widely separated and the trabeculae are thinned
• Acute splenitis


  Spleens of relatively normal size may contain multifocal small (1 to 2 mm diameter) foci of necrosis/suppurative infiltration
• Causes of acute splenitis

  • Tularemia (Franciscella tularensis)
  • Yersiniosis (Yersinia pseudotuberculosis)
• Gross findings of acute splenitis

  • Small white miliary foci scattered throughout the spleen. Similar lesions may be present in the lymph nodes and liver. Slightly larger older lesions may resemble granulomas
• Septicemic splenitis


  Marked splenomegaly - the spleen is soft, dark and engorged with viscous blood
• Causes of septicemic splenitis

  • Hog cholera (Classical swine fever)
  • African swine fever
  • Erysipelas
  • Anthrax
• Lymphocytolysis/Thymic atrophy

  Caused by malnutrition, drugs/toxins, or viral infections
• Thymic atrophy


  Normal with advancing age
• Thymic aplasia/hypoplasia

  Leads to loss or functional impairment of T cells and impaired cell-mediated immunity (primary/congenital immunodeficiency)
• Conditions with thymic aplasia/hypoplasia


  • SCID (severe combined immunodeficiency) in foals, mice, dogs
• Thymic hemorrhage/hematoma


  Sudden death due to hypovolemic shock resulting from massive thymic and mediastinal hemorrhage. Variety of causes have been implicated: trauma, ruptured aortic aneurysms, ingestion of anticoagulant rodenticide
• Thymic (Mediastinal) Lymphoma


  1. cell neoplasm, usually occur in younger animals (calves, cats, dogs)