There are several things you should look for when evaluating a bone marrow biopsy specimen – see if you can see them in the image above.
First, take a look at the cellularity. The white spaces are fat cells that have washed out during processing; the cells in between the fat cells are hematopoietic precursors. The ratio of cells to fat is called the “cellularity.” The marrow above is approximately 30-40% cellular. You need to know the age of the patient to estimate whether the cellularity is normal. Here is a rough guide to cellularity by age:
0-3 months: 100%
3 months – 10 years: 80%
20 years: 65%
30 years: 50%
40 years: 45%
50 years: 40%
60 years: 35%
70 years and over: about 30%
Next, take a look at the composition of the marrow. Myeloid cells make up the largest percentage of the normal marrow cellularity; erythroid cells are second most common. The ratio of myeloid to erythroid cells should be about 2:1 to 4:1. It’s easier to see these cells on an aspirate smear, but you can get a pretty good idea on the marrow section too. Neutrophils and precursors often have eosinophilic, granular cytoplasm; if you look closely, you can see the indented nuclei of metamyelocytes and segmented nuclei of mature neutrophils. Erythroblasts generally have very round, dark nuclei; earlier forms are large, and later forms are small. A few megakaryocytes (large cells with abundant eosinophilic cytoplasm and multiple nuclei) should be sprinkled throughout the marrow too. Lymphocytes normally represent about 10-15% of the marrow cellularity. The above marrow appears to have a myeloid:erythroid ratio of 2:1, and megakaryocytes are normal in number.
Finally, take a look through all the sections to see if you see anything weird, like fibrosis, metastatic carcinoma, lymphoid aggregates, or amyloid deposition. As you scan the sections, you should see evenly-distributed cellularity, with evenly-spread hematopoietic precursors. Anything that deviates from this pattern should be investigated on higher power.
- Dr.Govind said excellent explanation thank you very much.
- Dr.Govind said nice
- nouf said 🙂
- Dr Govind said very simple explanation thank u very much..
- Dr Govind said nicely explained.
- Ana said Dope!! I love your summary….keep it up
- Kristine said Hi Michelle – thank you so much for your kind words! I’m SO glad you find useful stuff o...
- Michelle Stoffel said From a second year pathology resident who has been a fan of your site since discovering it as a 3rd...
- abhiram said crisp nd clear….thnk u…..
- Nelmary said I Had the same confusion with myelosupression and aplastic anemia thanks for clarifying my doubt.
- Sameera said Thank u, simple and clear
- dr zubair DCP said thanx sir,i was tense,made me simple,i m grateful to u,nd proud of u,regard