JOURNAL PRESENTATION

Dr. Nasrin Akhter

Resident (Phase B)

Department of Haematology,

BSMMU

AUTHORS: Joffrey Feriel, François Depasse, Franck Geneviève.��FIRST PUBLISHED: 18^th November, 2019�on International Journal of laboratory haematology.

Introduction

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• Basophilia is a rare disorder of the complete blood count (CBC).

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• It is defined by a basophil count higher than the upper reference limit, which is commonly 0.1 × 10⁹/L and corresponds to less than 1% of total WBC.

Introduction

• In general practice, less than 0.1% of CBC shows basophilia.

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• The association between basophilia and myeloid neoplasm, especially chronic myeloid leukemia (CML) is well established.

• There is conflicting data on some benign medical conditions and it remains unclear where basophilia is present.

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Introduction

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• The basophil count is usually mildly increased for reactive basophilia (below 1 × 10⁹/L) and can range from mild to high increase for neoplastic basophilia (below or above 1 × 10⁹/L).

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• Hyperbasophilia (HB), which is defined by a basophil count exceeding 1 × 10⁹/L for at least 8 weeks , strongly suggests the presence of an underlying neoplasm .�

Objective

• will conduct a critical analysis of the literature to define which medical conditions can lead to basophilia and which cannot.
• Propose practical approach to manage basophilia in daily practice divided into 3 steps :

IS IT A REAL BASOPHILIA? �

• There are three methods to detect spurious basophilia-

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Hematology Analyser

• Different methods can be used to determine the basophil count.

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• Some manufacturers (Coulter and Abbott) count basophils in a common WBC differential channel.

• On the other hand, other manufacturers (Sysmex, Mindray, Siemens, and Horiba) count basophils in a specific channel using a specific lysis agent .

Hematology Analyser

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• Recently, Coulter has developed a method based on FCM with the use of monoclonal antibodies for the WBC differential, known as “Hematoflow method.”

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• In this case, separation of basophil with another WBC is based on the presence and intensity of expression of specific antigens.�

Hematology Analyser

• The basophil count is more often overestimated than underestimated.
• Three main causes of overestimation have been reported in the literature.

1.Delayed processing >24 hours.

2. On the “basophil” specific channel, basophils are separated from other WBC by their ability to resist the extended lysis. In some cases, other types of cells have the same ability and may,therefore, be falsely counted as basophils .

Hematology Analyser

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3. On the common WBC differential channel, all kinds of cells that can be located in the basophil area may be counted as basophils.

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Among them, we can point to degranulated neutrophils, NRBC and platelet clumps.

Hematology Analyser

Two main causes of underestimation have been reported in the literature :

Hematology Analyser

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• The International Society of Laboratory Hematology (ISLH) recommends a slide review in the presence of basophil count >0.5 × 10⁹/L for the first time.

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• In case of basophil count <0.5 × 10⁹/L, a slide review should be performed in case of suspicion of abnormal cells and platelet clumps.

Blood smear

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• The Aim of the blood smear is
• to confirm the basophilia,
• to assess the morphology of basophils, and
• To determine if there are clues of myeloid�neoplasm among others lineage. �

Blood smear

• Manual basophil count should be performed on at least 400 white blood cells, two 200-cell differential count.

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• This method is time consuming and has many biases including slide distribution error, morphological interpretation error and statistical error.

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• Use of a cell image analyser may be helpful to decrease bias due to statistical error and count�the adequate number of cells in an acceptable time.�

Blood smear- Morphology of Basophil

• size: same as neutrophils, ranging from 10 to 14 µm.
• cytoplasm : generally stains pinkish and contains purple-black and coarse granules, which often obscure the cell nucleus.
• nucleus of the basophils has a condensed chromatin and may be band-shaped or segmented into two lobes.
• Nucleoli are often absent.

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Blood smear

• Dysplastic basophils are usually seen in MDS and an accelerated phase of CML.

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• Abnormalities include degranulation, abnormal size or staining of granules, cytoplasmic vacuolization and nuclear hypersegmentation.

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• Other blood cells may be confused with basophils, especially neutrophils with toxic granulation and eosinophils with abnormal dark granules.

Flow cytometry

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• FCM is the most reliable method for basophil identification and quantification.
• On the CD45/SSC plot, basophils are located in the “Bermuda triangle”.
• The positivity of CD45 is usually dimmer than lymphocyte and brighter than myoblasts.
• CD203c is the most specific marker to identify basophil permit a reliable quantification in PB and BM.

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Flow cytometry

• After gating on CD45 moderately positive and low SSC cells, CD123 associated with HLA-DR seems to be a robust combination to identify basophils that are strongly positive for the first marker and negative for the second one.
• Moreover, this combination permits to separate basophils from plasmacytoid dendritic cells, which express bright HLA-DR.
• The distinction with neutrophils is obvious because�the latter exhibit a higher SSC. �

Flow cytometry

• They are both positive for CD13, CD33.
• Basophils express CD11b in half the cases and are negative for�CD16.
• Eosinophils and basophils are easily separated because eosinophils exhibit a higher SSC and express CD45 with higher intensity.
• In case of mast cell leukemia, expression of CD117 is the most widely used marker to distinguish mast cells, that are strongly positive, and basophils, that are negative.

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Flow cytometry

• Abnormal immunophenotype is a common finding for neoplastic basophils.
• Under-expression of CD38 is recurrent among CML�patients; some cases may also show aberrant expression of CD64, HLA-DR, and CD123.
• The immunophenotypic profile of basophils has also been studied for non-CML patients and abnormal expression of CD13, CD33, and HLA-DR are the most often reported.

SYMPTOMS THAT SUGGEST REACTIVE�BASOPHILIA �

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• Atopy can be associated with basophilia. In which increased number of circulating basophils is commonly correlated with the eosinophil count, with values never exceeding 1 × 10⁹/L.

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• Some studies have found a correlation between the basophil count and the intensity of symptoms, as for example with patients with allergic rhinitis for which basophilia is correlated with nasal symptoms.

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• A prospective study by Calbi et al evaluated the usefulness of basophil count in newborns at birth to predict development of atopic disorders.

• Several publications have confirmed that iron deficiency may be associated with mild basophilia in some cases.

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• Diabetic patients with a stable condition exhibit a higher level of basophil than nondiabetic population; interestingly, the basophil count is even higher for patients with diabetic ketoacidosis.

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• Spurious basophilia related to activated lymphocytes, which are quite common in some viral infections.
• Basophilia has been said to occur in many other medical conditions, such as tuberculosis, chicken pox, small pox, injection of foreign proteins, and cirrhosis.
• Numerous review articles mention hypothyroidism and parasitic infection as a possible etiology for basophilia. ��

Basopenia

Some medical conditions may be associated with Basopenia:

LOOKING FOR A NEOPLASTIC�BASOPHILIA �

Chronic myeloid leukemia

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• Basophilia is the most common abnormality on the CBC in CML.

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• It may be isolated and remain the sole manifestation in the CBC for several months or even in rare cases, several years.

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• Yasuda et al reported a case of CML in which an 80-year old man exhibited isolated mild basophilia that was confirmed on four occasions during a period of 27 months and with no sign of progression.

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Chronic myeloid leukemia

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• The intensity of the increased basophil count is�variable but a value above 1 × 10⁹/L is very suspicious of a CML.

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• Intensity of basophilia has few or no correlations with other characteristics (eg, splenomegaly, performance status).

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• The percentage of basophils in the PB and in the BM is an independent prognostic factor.

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Chronic myeloid leukemia

• A study by Kantarjian et al stated that patients with a higher percentage of circulating basophils have lower survival outcomes.
• Many authors suggest that an increased�number of basophils in PB might be an indicator of disease severity.
• The World Health Organization (WHO) and the�European Leukemia Net (ELN) define a percentage of circulating basophils greater than 20% as an accelerated phase criteria for CML.
• Moreover, the basophil count has been included in several prognostic scores, such as Sokal, Hasford,and EUTOS scores �

Chronic myeloid leukemia

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• It lead The World Health Organization (WHO) and the European Leukemia Net (ELN) to define a percentage of circulating basophils greater than 20% as an accelerated phase criteria for CML.

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• Moreover, the basophil count has been included in several prognostic scores, such as Sokal,Hasford, and EUTOS scores. �

Other hematologic neoplasms

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• Persistent basophilia confirmed on blood smear with no evidence of reactive context or CML leads to the prescription of second-line examinations.

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• These include :

Other hematologic neoplasms

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• The basophil count is higher in PMF patients than in�healthy controls.
• 50% of PMF patients exhibiting a basophilia�>0.1 × 10⁹/L.
• Moreover, the absolute basophil count seems to be�correlated with the severity of the disease and with the widely used Dynamic International Prognostic Scoring System (DIPSS).

Other hematologic neoplasms

• Basophils may be moderately increased in PV and ET.

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• In PV, the basophil count and the number of activated basophils (CD63+) seem to be correlated with the JAK2 V617F burden.

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• Aquagenic pruritus is a common feature of PV. The presence of this symptom is not linked to the basophil count but is associated with a significantly greater number of circulating activated basophils (CD63+). �

Other hematologic neoplasms

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• Hypereosinophilic syndrome (HES) should be considered if concomitant eosinophilia is present and the FIP1L1-PDGFRA fusion gene should be sought.

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• If molecular studies are inconclusive, additional genetic studies (including extended FISH panel and NGS) may help in determining the clonal nature of the disease. �

Other hematologic neoplasms

• BM aspiration with morphologic and cytogenetic evaluation permits diagnosis of CML-like disease, MDS, mixed MDS/MPN, acute leukemia, and basophilic leukemia.

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• An extremely rare CML-like disease�associated with t(9;12)(q34;p13) can be identified by this second-line examinations. This chromosomal abnormality results in the ETV6-ABL1 fusion gene that leads to a more aggressive phenotype than classical CML. �

Other hematologic neoplasms

• A study by Matsushima et al examined the presence and the prognostic significance of basophils in 288 patients with de novo MDS.
• Approximately 15% of patients with MDS exhibits BM basophilia and among them, a circulating basophil count above 0.1 × 109/L is observed in 42% of cases. The basophil count was below 1× 109/L in all cases.
• Whatever the cutoff used an increased basophil count is associated with reduced overall survival.
• No consensus hasbeen reached regarding the impact on the risk of developing AML.

Other hematologic neoplasms

• High level of PB basophils is often observed in MDS patients with specific chromosomal abnormalities, such as i(17q), t(6;9)(q23;q34.3), and complex karyotypes.

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• Interestingly, i(17q) is also observed in the�accelerated phase of CML,whereas t(6;9)(q23;q34.3) is a cytogenetic abnormality which defines a specific type of AML.

Other hematologic neoplasms

• A moderate basophilia is occasionally seen in mixed MDS/MPN, such as chronic myelomonocytic leukemia (CMML) and atypical CML.

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• Basophilic leukemias are extremely rare MPN which had been poorly characterized for many years.

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• To address this issue, an international expert group has proposed diagnostic criteria and a classification of basophilic leukemias in a consensus article published in 2017.�

Other hematologic neoplasms

• Chronic basophilic leukemia (CBL) is�characterized by HB combined with basophils ≥40% of BM or PB cells and the evidence that basophils belong to the malignant clone.

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• Primary and secondary CBL are distinguished, depending on the demonstration of an underlying myeloid neoplasm.

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• No recurrent cytogenetic or molecular abnormalities have been identified in primary CBL to date .�

Other hematologic neoplasms

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• AML accompanied by basophilia or�acute basophilic leukemia (ABL).

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• AML accompanied with basophilia may be associated with various genetic abnormalities. The most common genetic defect is the t(6;9)(p23;q34) but other abnormalities such as t(8;21)(q22;q22), t(X;6)(p11;q23) and chromosome 12p abnormality have also been reported in literature. �

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CONCLUSION

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