3._Bone_marrow__2024

Agenda

• Opening activity (1:25 PM)

• Hematology: Bone Marrow (2:30 PM)

• Week 3 Cases & Closing Activity (2:55 PM)

• Exit Question (3:05 PM)

Opening Activity

• Duration: 10 minutes (Starting at 1:25 PM)

Laboratory Evaluation of Bone Marrow

• Course: VETC 306 Clinical Pathology

• Instructor: Dr. Sabrina Timperman

Bone Marrow Overview

• Definition: Tissue enclosed by cortical and cancellous bone.

  • Composed mainly of hematopoietic cells, adipose tissue, and supportive tissue.

• Red Bone Marrow:

  • Site of hematopoiesis. Initially, all bone marrow is red, transitioning to yellow with aging.

  • Adult sites include: proximal humerus, femur, sternum, ribs, vertebral bodies.

• Yellow Bone Marrow:

  • Primarily fatty tissue with no hematopoietic function but can revert to red in certain conditions.

Hematopoietic Cells

• Definition: Precursors to hemic cells found in blood or tissue.

  • Consists of cells in the mitotic (proliferation) pool and post-mitotic (maturation) pools.

• Lineages:

  • Erythrocyte lineage.

  • Leukocyte lineage.

  • Megakaryocyte lineage.

Reasons to Examine Bone Marrow

• Diagnosing hematologic abnormalities, including:

  • Nonregenerative anemia.

  • Neutropenia.

  • Thrombocytopenia.

  • Persistent thrombocytosis or lymphocytosis.

  • Abnormal blood cell morphology or unexplained immature cells presence.

  • Determine regenerative status of anemia in horses.

  • Stage neoplastic conditions like lymphoma and mast cell tumors.

Aspirate vs. Biopsy

• Aspirate:

  • More frequently performed; easier and faster.

  • Stained and examined by pathologist; less expensive.

• Core Biopsy:

  • Uses bone biopsy needle to obtain a solid core.

  • More accurate evaluation of cellularity and metastatic neoplasia but harder to assess cell morphology.

Contraindications

• Few contraindications exist:

  • Patients with hemostatic diathesis.

  • Post-aspiration hemorrhage is rare and can be controlled.

• Risks include:

  • Hemothorax or cardiac tamponade in horses with clotting disorders.

  • Potential post-aspiration infection; requires sterile technique.

Common Bone Marrow Aspiration Sites

• Dogs:

  • Proximal humerus.

  • Trochanteric fossa of proximal femur.

  • Iliac crest.

• Cats:

  • Proximal femur and proximal humerus.

  • Accessibility makes these sites preferable.

• Horses, Cattle, and Camelids:

  • Common sites: ilium, ribs, sternum.

Bone Marrow Aspiration Technique

• Requires general anesthesia or sedation; local anesthesia is standard.

• Surgical preparation involves making a small skin incision with a scalpel blade.

• Bone marrow needle is rotated into the bone until seated.

• Remove stylet, attach syringe, apply negative pressure until marrow is visible in the barrel.

Slide Preparation for Analysis

• Smears must be prepared quickly, in seconds if no anticoagulant is used.

• Slides should be thinly distributed; smear preparation involves holding slides vertically to absorb blood and particles.

• Stained with Romanowsky stain; air-dried before analysis.

Bone Marrow Core Biopsy

• Utilizes a Jamshidi needle for core biopsy from proximal femur, proximal humerus, or ilium.

Erythroid Series

• Overview:

  • Differentiation from myeloid stem cells to BFU-E and then CFU-E cells.

  • Erythropoiesis Process:

    • Rubriblast->Prorubricyte->Rubricyte->Metarubricyte->Reticulocyte->Mature erythrocyte.

  • Important stages of maturation include decreasing cell size, nucleus changes, and cytoplasm color changes.

  • Normal stem cell to RBC release time: 3-5 days.

Regulation of Erythropoiesis

• Erythropoietin (EPO): Secreted mostly from kidneys, especially in response to hypoxia.

• Other hormones affecting erythropoiesis: androgens, glucocorticoids, insulin, growth hormone promote; estrogen inhibits.

Granulocyte Series

• Characterized by granules in the cytoplasm:

  • Types: Neutrophils, Eosinophils, Basophils.

• Maturation sequence from immature to mature includes:

  • Myeloblast->Promyelocyte->Myelocyte->Metamyelocyte->Band granulocyte->Segmented granulocyte.

Monocyte Series

• Few in concentration; hard to distinguish from myeloid lineage in normal bone marrow.

• Maturation includes Monoblast and Promonocyte stages transitioning to mature Monocyte.

Megakaryocyte Series

• Large, multinucleated cells becoming platelets.

• Maturation includes Megakaryoblast and Promegakaryocyte stages leading to mature Megakaryocyte.

Other Cells in Bone Marrow

• Includes Lymphocytes, Plasma cells, Macrophages, Osteoblasts, Osteoclasts, and Mast Cells.

• Lymphoblast presence is indicative of lymphoproliferative disorders.

Approach to Bone Marrow Evaluation

• Use low power objective (100x) to scan for overall cellularity and assess adequacy of sample.

• Normal marrow is heterogeneous; increased fat vs. nucleated cells indicates abnormal populations.

• Examine the ratio of granulocytic to erythroid cells (Myeloid to Erythroid Ratio - M:E) by counting 500 cells.

Stem Cell Disorders of Marrow

• Reversible Stem Cell Injuries:

  • Usually transient; caused by viral agents, chemotherapeutics, or chemicals affecting rapidly dividing cells.

  • Results in neutropenia, thrombocytopenia, and nonregenerative anemia; recovery expected after a couple of weeks.

• Irreversible Stem Cell Injury:

  • Caused by FeLV in cats or unknown factors in other animals; can result in aplasia, dysplastic production, or neoplastic production.

  • Myelodysplasia represents abnormal development leading to cytopenias, more common in cats.

Neoplastic Disorders in Bone Marrow

• Myeloproliferative Neoplasia: Neoplastic proliferation from cells in the marrow including various leukemias.

• Lymphoproliferative Neoplasia: Derived from lymphocytes, with types such as acute lymphoblastic leukemia and plasma cell myeloma.

• Broad classification of leukemias into acute (rapid progression, replacement by blast cells) and chronic (milder progression with some retained function).

• Management and prognosis vary significantly between acute and chronic presentations.