Key Takeaways

• Differential diagnosis of hematological disorders is complex, requiring several tests and samples to reach a diagnosis. 
• Bone marrow examination (BME) is essential for the diagnosis and prognosis of various conditions including several types of Leukemia, anemia, myelodysplastic syndromes, and unexplained cytopenia. 
• Bone marrow aspiration (BMA) provides rapid and detailed cytologic insight, is diagnostic for many conditions and has fast turnaround times (TATs), in time sensitive and often life-threatening diagnoses.
• Bone marrow biopsy (BMB) is often needed in combination with BMA, as well as PBS and clinical evaluation to confirm the final diagnosis in many conditions.
• Advanced methods such as flow cytometry, FISH and NGS can enhance diagnosis and prognosis capabilities. 
• Artificial intelligence (AI) and digital decision support platforms with multiple diagnostic tools may further enhance diagnostic capabilities in the future, allowing for faster, clearer diagnoses to support optimal clinical decision and outcomes.

Differential diagnosis in hematology

The diagnosis of many hematological conditions is complex and challenging, often requiring a combination of several laboratory tests, imaging, and pathology-based tests. Among the most critical tools is bone marrow examination which includes cytological assessment using aspirate (BMA), and histological evaluation using bone marrow biopsy (BMB). ¹  These tests provide complementary and essential information about cell morphology, lineage counts and genetic abnormalities, as well as bone marrow architecture which enable the distinction between different conditions and guide clinical decisions. ^1–3

More about BMA

A bone marrow examination (BME) refers to the combined use of bone marrow aspirate (BMA) and bone marrow biopsy (BMB) to evaluate marrow health and disease. The aspirate involves withdrawing liquid marrow to assess detailed cytology—such as cell morphology, differential counts, and presence of abnormal cells—providing excellent cellular detail. In contrast, the core biopsy retrieves a solid piece of marrow, allowing examination of the overall marrow architecture, cellularity, fibrosis, and the presence or pattern of focal lesions or infiltrates. Together, these complementary procedures provide a more complete and accurate picture of the bone marrow pathology, therefore, in many cases collecting both samples is recommended.³

Indications for Bone Marrow Aspiration (BMA)

Bone marrow aspiration is indicated by the International Council for Standardization in Hematology (ICSH)  as the method of choice for several indications described below. ^1,4

Major indications include:

• • Diagnosis of hematological malignancies: BMA is useful in the diagnosis of leukemia, multiple myeloma, myeloblastic syndrome and lymphoma by enabling rapid assessment of malignant cell morphology and lineage. 
  • Staging and monitoring of malignancies: Aspirations help assess response to treatment and detect remission state.

• Investigation of abnormal blood counts:  Unexplained anemia, cytopenia, s and abnormal blood morphology often require marrow evaluation to identify underlying causes which include acute leukemias, chronic leukemia, megaloblastic anemia, and marrow failure syndromes where a uniform marrow involvement.

• Assessment of treatment response: BMA helps to evaluate the efficacy of chemotherapy or radiation efficacy in treatment of hematological malignancies.

• Detection of systemic infections: Certain infections such as leishmaniasis, malaria and cryptococcus can be detected in the bone marrow, when going undetected in the peripheral blood.
• Evaluate iron stores status: Iron staining on aspirate samples enables direct visualization of iron stores, providing a more reliable assessment that is less influenced by inflammatory conditions than serum ferritin levels.
• Donor evaluation for bone marrow transplant: perform evaluations of BM cells prior to bone marrow donation.

BMA Limitations

Despite being a rapid and comprehensive test for bone marrow examination, BMA still holds several limitations and complexities.

1. Overlapping morphology– In some cases morphology is not sufficiently distinguishable to provide a definitive distinction between different diseases. This may occur in cases of benign or malignant cells, infectious diseases- may require the use of other methods such as flow cytometry^.2
2.  Focal disease– localized lesions may be missed, leading to false negative results, particularly in metastases and lymphomas. ^1–3
3. Technical limitations– Issues such as hemodilution, poor smear preparation, cell lysis, or insufficient staining can affect diagnostic accuracy^.2
4. Myelofibrosis and “dry tap”- fibrosis is common in advanced stages of CML or primary myelofibrosis. This can lead to inadequate aspiration (Dry Tap), which may lead to inaccurate blast count. ^2,3

Diseases where BMA is essential

Acute myeloid Leukemia (AML)

Bone marrow examinations are often sufficient for diagnosing AML due to the diffuse state of cells. The guidelines European Leukemia Net (ELN), the National Comprehensive Cancer Network (NCCN) Guidelines, and the World Health Organization (WHO) 2016 guidelines recommend using BMA for cytomorphology, blast count, and lineage markers in combination with flow cytometry, FISH and other molecular assays. 

Although circulating blasts may allow preliminary diagnosis using peripheral blood, bone marrow remains the gold standard methods for disease classification and risk stratification. Minimal residual disease cannot be performed based on morphology assessment alone and requires advanced methods such as flow cytometry^.5

Chronic Myeloid Leukemia (CML)

In CML, diagnosis often begins with peripheral blood testing, including CBC, morphology, and detection of the Philadelphia chromosome (A unique genetic feature of CML.⁶⁾.However, complete diagnosis and staging of the disease by BMA is required. The aspirate is used to perform several tests including morphology test and blast count to assess disease stage as well as karyotype and molecular analysis to determine the BCR-ABL1 transcript levels and test for BCR-ABL1 genomic abnormalities in the Philadelphia chromosome. While biopsy is not routinely needed for initial diagnosis, it may be required in advanced phases. ^2,3,6

Non-neoplastic anemias and nutritional deficiencies

While BMB is not routinely needed for initial diagnosis, it may be required in advanced phases Similarly to other leukemias, it provides a rapid analysis of cell morphology which can be served for initial diagnosis.^1,3

• Aplastic Anemia- Marrow appears hypocellular with fatty replacement, requiring both aspiration and biopsy for confirmation. ⁷
• Myelodysplastic Syndromes (MDS)–Marrow studies assist in the identification of  cytopenia, dysplasia, blast percentage and genetic abnormalities. ⁹
• Hemophagocytic Lymphohistiocytosis (HLH): hemophagocytosis a key criterion of HLH can be observed in samples from BM aspiration, but cannot confirm diagnosis alone due to its non-specific nature. ⁸

Nutritional deficiencies where BMA is essential:

• Iron Deficiency-The initial most commonly used method of iron deficiency diagnosis is CBC combined with serum ferritin and transferrin saturation (TSAT). In certain complex cases, e.g. in cases of patients with inflammatory conditions, other methods are used. In these conditions,  BMA is the superior to BMB for determining storage iron status since decalcification, which dissolves non-heme iron, is not performed, unlike biopsies where the process is required.  Iron stains on BMA, such as Prussian blue stains, provide a more sensitive and reliable evaluation of storage iron and identification of ring sideroblasts when compared to BM biopsy sections. ¹⁰
• Megaloblastic Anemia– Similarly to iron deficiency, when megaloblastic anemia is suspected, several tests are performed including CBC, reticulocyte count and vitamin B12 and folate levels. To complete the diagnosis an aspirate is used-to identify the cells’ distinct maturation features- “Megaloblasts”.⁽¹¹⁾ Megaloblastic Anemia is easily diagnosed on aspirates with distinctive nuclear-cytoplasmic asynchrony. ³

Need for Integration of Multiple Diagnostic Methods

Due to the complexity of hematological conditions and diseases, several sample types are needed for accurate diagnosis, which is a key determinant of treatment options and optimized clinical outcomes. While aspiration provides rapid cellular analysis, biopsy is essential for detecting fibrosis, granulomas, tumor infiltrates and focal lesions. ¹ Using the integrated approach, combining peripheral blood smear (PBS) together with bone marrow aspirate (BMA), bone marrow biopsy (BMB), flow cytometry, and other methods provide a comprehensive disease profile. Examples where combining samples improves diagnosis include:  Focal diseases- Random aspiration can miss cellular infiltration, therefore BMB is required to complete the diagnosis ^2,3 ; a fibrotic state may lead to “dry tap”, where there are insufficient cells for an aspirate, thus requiring a biopsy. ^12,13

Integration of advanced cytochemistry, immunophenotyping, cytogenetics and molecular genetics testings can expand the understanding of the disease state and further enhance the diagnostic capabilities. Several methods have been integrated into current disease guidelines and include:

• Flow cytometry– Enables highly accurate and highly sensitive lineage assessment, discovery of aberrant phenotypes and accurate measurement of minimal residual disease (MDR).^1,5,14
• FISH and karyotyping– identifies chromosomal aberrations, such as BCR-ABL1inversions and translocations at the t (8;21) or t (15;17) in CML patients. These assays can be easily performed using BMA samples due to the preparation process which does not require decalcification that destroys nucleic acids (DNA and RNA).¹
• Molecular assays such as PCR, RT-PCR and next generation sequencing (NGS) detect somatic mutations which can further assist in prognosis and treatment selection in AML patients. ^1,3

Although integrating these methods is crucial for increasing the sensitivity of diagnosis, they have several limitations:

• They extend the turnaround time (TAT)- one major advantage of BMA is the rapid TAT for morphological assessment within a few hours, rather than waiting on a BMB which can take days. This is particularly important in life threatening malignancies, such as acute leukemia and multiple myeloma, where treatment needs to be started almost immediately. Implementing traditional advanced testing ( flow cytometry, genetic and molecular testing) may increase TATs from minutes to several hours or even longer.^1,2,5
• Using these methods requires expertise both from the pathology lab as they require complex equipment and skills, as well as from the clinician, who evaluates the results. ^1,2,5,6

Artificial Intelligence (AI) based analysis can further enhance the integrative approach by providing an automated, rapid and accurate analysis of bone marrow samples. AI- based tools can further improve the identification and classification of cell types, reduce the inter-observer variability and standardize the preliminary diagnosis.¹⁵ This integration of AI complements traditional cytomorphology, immunophenotyping, and molecular testing, thereby strengthening the diagnostic precision and efficiency in hematologic and bone marrow-related diseases.

The Scopio Full Field–Bone Marrow Aspirate™ application is the first digital platform built specifically for comprehensive BMA evaluation, providing full-field review at 100× magnification. The Scopio platform combines clinical-grade Full-Field imaging at 100× oil-immersion resolution with an AI-driven decision-support engine, enabling high-quality remote analysis and reporting without compromising diagnostic standards.¹⁸

* Scopio’s Full-Field remote capabilities are available through the secure hospital network.

References:

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