Bone marrow mast cell quantification has proven beneficial in differentiating aplastic anemia (AA) from hypoplastic myelodysplastic syndromes (MDS), according to findings from a time-bound, retrospective study conducted in the department of pathology, Kasturba Medical College, Mangalore, India.
Results of the analysis were published in the journal F1000Research.
With the clinical and morphologic features of hematologic disorders that present with hypocellular bone marrow, such as hypoplastic MDS (MDS-h) and AA, overlapping diagnostic challenges are often reported. Differentiating between the 2 disorders is crucial, however, with both AA and MDS-h having varying outcomes, prognoses, and management protocols. In fact, compared with individuals with AA, patients with MDS-h experience shorter median survival rates and have a weaker response to immunosuppressive therapy.
The researchers of the current study sought to investigate the distribution of mast cells in hypoplastic bone marrow and to establish its role in the differential diagnosis of AA vs MDS-h.
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All hypoplastic/aplastic bone marrow biopsies received between January 2015 and December 2021 were included in the analysis. Sixty-five cases fulfilled the study inclusion criteria of adequate bone marrow biopsy measuring 1 cm or more in length with a minimum of 4 marrow spaces. Hematoxylin and eosin-stained tissue samples were examined to evaluate the cellularity and identify the morphology of the bone marrow. The cases were categorized as AA, MDS-h, or hypoplastic marrow (HM) due to any other cause.
Quantification of mast cells was performed via identification of metachromatic granules in mast cell cytoplasm. Immunohistochemistry for CD34 was carried out on paraffin-embedded, formalin-fixed tissue that underwent morphologic assessment.
Of the 65 cases examined, 32.3% (21 of 65) were diagnosed as AA, 18.5% (12 of 65) were diagnosed as MDS-h, and 49.2% (32 of 65) were diagnosed as HM. Overall, 32.3% of the study population comprised individuals from the pediatric and adolescent population; 28.7% of the cases were reported in patients aged over 60 years. The remainder of the cases were in the 20- to 60-year-old age-group. The male-to-female ratio in the study population was 1.6:1, with 40 of the cases in males and 25 in females.
Mast cells in the bone marrow were highlighted by staining with Toluidine blue. Results of the study revealed that over 1% of mast cells was observed in 55.4% (36 of 65) of the total cases. In 10.8% (7 of 65) of the cases, over 10% of mast cells was seen. A mast cell count over 1% was considered to be increased.
Elevated numbers of mast cells were seen in 48% of cases of AA, 31% of cases of HM, and 21% of cases of MDS-h
(P =.040). In all, 76% of cases of AA and 33% of cases of MDS-h exhibited increased numbers of mast cells. Decreased hematopoietic stem cells were observed in 69.4% of the cases with elevated numbers of mast cells (P =.10).
“Mast cell quantification in the [bone marrow] biopsies with the help of TB special stain can act as a supplementary tool to distinguish the  entities, as mast cells are increased in the majority of cases of AA, [whereas they are] increased only in a few cases of MDS-h,” the researchers concluded.
Chaithra GV, Gupta S, Rao R, Rai S, Murali N, Hegde S. Diagnostic utility of mast cell analysis in hypoplastic bone marrows for differentiation of aplastic anaemia from hypoplastic myelodysplastic neoplasm: a retrospective study. F1000Research. Published online July 13, 2023. doi:10.12688/f1000research.130876.1