Normal Cellularity for the Bone Marrow Biopsy

 

The cellularity varies with location of biopsy.

(1) The vertebral body is about 10% more cellular than iliac crest.

(2) The sternum can show variable cellularity relative to the iliac crest.

(3) The rib tends to have a lower cellularity than the iliac crest.

 

Cellularity of hematopoietic tissue as percent of marrow space:

(1) Normally most nucleated cells are hematopoietic

(2) Infiltration by lymphocytes, plasma cells, tumor cells, etc. can reduce relative percent of hematopoietic cellularity

 

Cellularity:

(1) decreases with age

(2) This is a combined effect of decreased hematopoietic tissue and a reduction in bone.

(3) Adipose tissue fills the nonhematopoietic marrow cavity.

 

Reference range for hematopoietic cellularity from iliac crest

Age in Years	Upper Limit	Mean	Lower Limit
0 - < 10	95.1%	78.8%	59.0%
10 - < 20	86.6%	64.3%	41.5%
20 - < 30	83.7%	58.0%	32.0%
30 - < 40	81.3%	47.6%	30.3%
40 - < 50	75.1%	48.2%	16.3%
50 - < 60	73.6%	46.3%	19.7%
60 - < 70	65.7%	45.7%	16.3%
70 - < 80	47.1%	28.9%	11.3%

 

Interpretation:

• Cellularity may be considerable affected by technical factors.

• Cellularity less than 20% tends to indicate hypoplasia, except in elderly.

• Cellularity more than 80% tends to indicate hyperplasia, except in patients under 20 years of age.

• A cellularity of 25-75% is usually normal cellularity for patients 20-70 years of age.

 

Myeloid-to-Erythroid Ratio

 

myeloid-to-erythroid ratio =

= (cells in myeloid series) / (erythroblasts)

 

Interpretation:

• normal ratio: 1.2:1 to 5:1

• An increased ratio is seen in granulocytic hyperplasia (leukocytosis, myeloproliferative disorders) or depressed erythropoiesis.

• A decreased ratio seen in depressed leukopoiesis or erythroid hyperplasia.

 

Megakaryocytes

 

In bone marrow smears of good cellularity, normally 1-3 megakaryocytes are seen per 100x (10x objective, 10x ocular) field.