Bone marrow is the site of hematopoiesis in postnatal life. It is located within the cavities of the bones and mainly consists of hematopoietic cells, vascular sinusoids, fibroblasts, fat cells, and macrophages. There are no lymphatic channels in the bone marrow
There are two types of marrow: red and yellow. Red marrow refers to the active hematopoietic tissue while fatty tissue comprises the yellow (inactive) marrow. Red coloration is due to presence of large amounts of developing red cells. The average volume of bone marrow (red and yellow) in an adult is 3000–4000 mL.
Hematopoiesis occurs extravascularly in between interconnecting marrow sinusoids. The marrow sinusoids are lined by endothelial cells and are covered partially by cytoplasmic processes of fibroblasts. After development, mature blood cells leave the bone marrow and enter the circulation by passing through or in between the endothelial cells of the sinusoids Marrow fibroblasts (‘reticular cells’) are highly branched cells, which form reticulin fibers and form a supporting framework for the hematopoietic cells. Accumulation of lipid in reticular cells is said to produce fat cells of the bone marrow.
There are two techniques for sampling of bone marrow: aspiration and biopsy. In aspiration, bone marrow fluid is obtained by a special needle and syringe. Smears from this material are prepared on glass slides, stained, and examined under the microscope. In bone marrow trephine biopsy (core biopsy), a small tissue piece of bone marrow is removed with a special needle, processed to obtain histological sections, and examined.
INDICATIONS FOR BONE MARROW EXAMINATION Before performing bone marrow aspiration/biopsy, one should assess clinical features, treatment received, and relevant laboratory test results.
Indications for Bone Marrow Aspiration Unexplained cytopenia : Anemia, leukopenia, or thrombocytopenia. (a) To distinguish amongst causes anemia (b) In leucopenia or thrombocytopenia, bone marrow examination is helpful in distinguishing peripheral destruction from deficient production.
2. Unexplained polycythemia , leucocytosis, thrombocytosis : "is can reveal myeloproliferative neoplasm. 3 . Evaluation of iron stores for diagnosis of iron deficiency anemia or to distinguish it from anemia of chronic disease; demonstration of ringed sideroblasts in myelodysplastic syndrome or sideroblastic anemia 4. Suspected acute leukemia
5. Suspected myelodysplastic syndrome. 6. Suspected myeloproliferative disorders including chronic myeloid leukemia , polycythemia vera, essential thrombocythemia, and myelofibrosis. 7. Suspected plasma cell dyscrasia : multiple myeloma is suspected from clinical and radiologic features.
8. Suspected like chronic lymphocytic leukemia . 9. Investigation of pyrexia of unknown origin 10. Suspected storage disorder like Gaucher’s disease or Neimann -Pick disease.
11. Suspected infections like Kala-azar, miliary tuberculosis, or histoplasmosis. 12. For ancillary investigations like flow cytometry, cytogenetic or molecular analysis. 13. To monitor response to therapy and to assess remission or relapse.
Indications for Bone Marrow Biopsy 1. Repeated failure of aspiration (‘dry tap’) which may be due to faulty technique, fibrosis (metastatic carcinoma, Hodgkin lymphoma, primary myelofibrosis), hairy cell leukemia . 2. Suspected aplastic anemia . 3. Suspected myelofibrosis . 4. Suspected focal lesions like granuloma, metastatic deposit, or infiltrate of lymphoma. 5. Suspected hairy cell leukemia . 6. Suspected bone disorder, e.g. osteopetrosis. 7. Staging of lymphoma.
CONTRAINDICATIONS Hemophilia coagulation disorders however, in these patients it can be performed under cover of appropriate replacement therapy.
SITES FOR BONE MARROW ASPIRATION OR BIOPSY Iliac spines or crest The most frequently used site in children (>1 year of age) as well as in adults is posterior iliac crest (posterior superior iliac spine). This site has a large reservoir of marrow. Also, there are no vital structures including large blood vessels or nerves close to this area.
In obese patients, anterior superior iliac spine Sternum: Previously, sternum was commonly used for aspiration of bone marrow in adults (at the level of second intercostal space in midline). However, it is associated with the risk of perforation of underlying large blood vessels and right atrium with serious consequences. Core biopsy is not done at the sternum.
Spinous processes of lumbar vertebrae: This is an additional site for aspiration in adults. • Tibia: In infants under 1 year of age, marrow can be aspirated from the medial aspect of upper end of tibia just beneath tibial tuberosity.
METHOD Bone Marrow Aspiration Informed consent should be obtained before the procedure. Bone marrow aspiration or biopsy should be performed by the physician.
2. A sterile tray bone marrow aspiration needle, disposable syringes with needles, local anesthetic solution, clean and dry glass slides, spreader slide, gloves, drapes, gauze, and a skin antiseptic solution. All aseptic precautions should be observed during the procedure. Salah and Klima needles are commonly used. Salah needle has a guard with a side screw, while Klima needle has a guard which screws along the length of the needle.
Guards on these needles are adjustable to control the depth of penetration. Jamshidi needle, which is longer, can be used for both aspiration and biopsy from iliac crest.
3. For aspiration from posterior superior iliac spine, patient should lie on one side with, knees and hips flexed, and the knees drawn towards the chest. the site for aspiration should be selected and scrubbed with antiseptic solution. 4. Skin and periosteum are infiltrated with a local anesthetic.
5. After waiting for 5 minutes for anesthesia to take effect, bone marrow aspiration needle is inserted along with the fitted stylet. When the bone is reached, the needle is rotated clockwise and anticlockwise and slowly advanced into the bone, maintaining steady and “firm pressure.
6. A 5- or 10-mL syringe is attached to the needle and a small amount of marrow is aspirated by quickly pulling the plunger of the syringe. Aspiration is associated with sharp pain (suction pain). Aspiration of larger amount of blood causes dilution of marrow sample by peripheral blood with subsequent diffculties in interpretation of smears. If no material is aspirated, stylet is replaced, needle is redirected, and aspiration attempted again.
7. If immunophenotyping or cytogenetic analysis is to be carried out. 8. After completion of aspiration, the stylet should be reinserted into the needle and the needle is removed. Sterile gauze is placed over the site and light pressure is applied till bleeding stop.
COMPLICATIONS OF BONE MARROW ASPIRATION AND/OR BIOPSY 1. Local infection 2. Hemorrhage
Bone marrow aspiration provides following information: • Assessment of morphology of bone marrow cells • Assessment of nature of hematopoiesis • Cytogenetic analysis • Immunophenotyping of abnormal cells in leukemias . • Cytochemistry for typing of leukemia • Iron stain for assessing iron stores and sideroblasts • Microbial culture, e.g. for tuberculosis.
Bone Marrow Trephine Biopsy Bone marrow biopsy provides following information: Cellularity of bone marrow Bone marrow architecture Bone structure Marrow “fibrosis Focal lesions (granulomas, metastatic deposits, infilltration by lymphoma).
Examination of marrow smear consists of assessment of following features: • Cellularity • Differential count • Myeloid: Erythroid ratio • Erythroid series: Maturation sequence, type of maturation ( normoblastic,micronormoblastic , megaloblastic), cytologic abnormalities. • Myeloid series: Maturation sequence, cytologic abnormalities
• Megakaryocyte series: Number, abnormal forms • Lymphocyte series • Plasma cell series • Abnormal cells: Blasts, carcinoma cells and necrotic cells • Parasites: Malaria parasites, microfilaria, Leishmania donovani , and Histoplasma
• Iron content of marrow (on iron stain). Romanowsky-stained smears • Cellularity of marrow particles • Number of megakaryocytes • Focal metastatic deposits • Cell distribution and selection of suitable area for detailed cytologic examination.