Megakaryocyte Density Revisited.
Jean M Coviello-Malle, Neslihan Cetin, Marwan Yared. University of Arkansas for Medical Sciences, Little Rock; Arkansas Children's Hospital, Little Rock
Background: Published normal megakaryocyte (MK) density values vary from 1 to 5 MK per cellular hpf (40X). The investigators observed that pediatric marrows often exhibit higher MK densities than expected. In older patients, evaluation of fields with 100% cellularity is not feasible due to age-related increase in fat. Previous studies reported MK density in histologic sections, aspirated sternal marrow via hemocytometer, cytospin preparations, and cell suspension in terms of MK per 10,000 cells, mm3, or mm2. While these units of density might be useful for research, they are impracticle for use by practicing pathologists. In order to devise a new guideline for the practicing pathologist in evaluation of pediatric marrows and less cellular marrows, we examined 30 random hpf in each of 51 bone marrows from normocellular patients, using a 40x ocular lens on an Olympus BX51 microscope (field diameter 0.55mm).
Design: The records of 2 hospitals were searched for normocellular pediatric and adult bone marrow studies with a core biopsy of adequate length. Excluded from the study were patients with thrombocytosis, thrombocytopenia, recent or current infection, cirrhosis, or biopsy involvement by lymphoma or leukemia. Core biopsies had been fixed in AZF, decalcified in Surgipath Decalcifier II for 1/2 hour, processed overnight, and paraffin embedded. 5 micron H&E sections with #1 coverslips (0.13-0.16mm) were reviewed. 3 evaluators each examined 10 40x hpf. MK were counted if part of the nucleus could be seen. Each examiner estimated the overall cellularity, all values were averaged.
Results: A visual depiction of MK counts and cellularity vs. age can be seen in figure 1. The average MK count for 0-10 year old patients was 6 per 10 hpf. Between 10 and 20 years of age, the average count was 4/hpf, and more consistently fell within the expected range (5/11 cases). After 30 years of age, the count fell within expected range more consistently.
Conclusions: The MK count in relation to cellularity was relatively constant throughout the entire age range. Our study suggests that MK count decreases with age until about age 30, and thereafter levels off around 2-4 MK/hpf. In older patients, the MK count was within expected range, despite low cellularity.
Tuesday, March 1, 2011 1:00 PM
Poster Session IV # 160, Tuesday Afternoon