Year : 2009 | Volume
: 52 | Issue : 3 | Page : 421--423
Hypergranular precursor B-cell acute lymphoblastic leukemia in a 16-year-old boy
Prashant R Tembhare, PG Subramanian, Kunal Sehgal, Badrinath Yajamanam, Ashok Kumar, Sumeet Gujral
Departments of Pathology and Hematopathology Laboratory, Tata Memorial Center, Mumbai, India
Prashant R Tembhare
Departments of Pathology and Hematopathology Laboratory, Tata Memorial Center, Mumbai
Presence of cytoplasmic granules in the blasts is a well known feature of myeloid leukemia. ALL presenting with the numerous cytoplasmic granules in blasts is a rarity and may be misdiagnosed as acute myeloid leukemia. We describe a rare case of hypergranular precursor B-cell acute lymphoblastic leukemia (ALL) in an adolescent male expressing CD10, CD19, CytoCD22, CD34, as well as CD13 and CD117. The blasts were cytochemically negative for myeloperoxidase (MPO), and acid phosphatase (ACP) but were positive for non-specific esterase (NSE). In centers where immunophenotypic panel is usually decided on the basis of morphology with limited antibodies may result in an erroneous typing of such rare diseases. Hence it is important to be aware of this rare entity and to confirm the lineage of acute leukemia by using a comprehensive panel of antibodies for immunophenotypic analysis.
|How to cite this article:|
Tembhare PR, Subramanian P G, Sehgal K, Yajamanam B, Kumar A, Gujral S. Hypergranular precursor B-cell acute lymphoblastic leukemia in a 16-year-old boy.Indian J Pathol Microbiol 2009;52:421-423
|How to cite this URL:|
Tembhare PR, Subramanian P G, Sehgal K, Yajamanam B, Kumar A, Gujral S. Hypergranular precursor B-cell acute lymphoblastic leukemia in a 16-year-old boy. Indian J Pathol Microbiol [serial online] 2009 [cited 2019 Oct 14 ];52:421-423
Available from: http://www.ijpmonline.org/text.asp?2009/52/3/421/55014
Diagnosis of acute leukemia has traditionally been based on morphological and cytochemical evaluation of peripheral blood or bone marrow aspirate smears.  This is especially true in the resource poor centers where advanced techniques like immunophenotyping, molecular analysis, and cytogenetic analysis are not available. Presence of azurophilic cytoplasmic granules is an important morphological clue to diagnose acute myeloid leukemia (AML) and hypergranularity is a prominent feature of abnormal promyelocytes in acute promyelocytic leukemia (APML).  Rarely, however, the blasts in cases of acute lymphoblastic leukemia (ALL) may show the similar cytoplasmic granules mimicking myeloblasts resulting in a misdiagnosis of AML. ,
A 16-year-old boy was admitted with a history of fever, bony pain, weakness and anorexia for fifteen days, followed by blurring of vision for two days. Physical examination revealed bilateral cervical lymphadenopathy, hepatomegaly measuring 2cm below the right costal margin and splenomegaly measuring 3cm below the left costal margin. Complete blood count revealed hemoglobin of 41.1g/L, platelets count of 14.80 x 10 9 /L, total leukocyte count of 102x10 9 /L. Differential count performed on Wright's stained peripheral blood smear revealed 95% blasts and 05% lymphocytes. The blasts were 4 to 6 times the size of small mature lymphocyte, having moderate amount of deep basophilic cytoplasm, round to oval nuclei with one to two conspicuous nucleoli. The cytoplasm had numerous small azurophilic granules in almost 80% of the blasts [Figure 1]. No Auer rods were seen. So on morphological grounds, a diagnosis of AML with possibility of APML was kept. But the blasts were negative for myeloperoxidase, acid phosphatase and Periodic Acid Schiff's (PAS) test, and were positive for nonspecific esterase [Figure 2]. Hence we considered the other differential diagnosis such as acute monoblastic leukemia (AML-M5a) or a rare possibility of Plasmacytic leukemia with azurophilic inclusions. Immunophenotypic analysis by flow cytometry using a comprehensive panel including cytoplasmic markers was done and to our surprise, it revealed positivity for CD19 (HIB19), CD10 (HI10a), cyto CD22 (HIB22), CD13 (WM15), CD117 (YB5.B8), HLADR (G46-6), and CD34 (581). But MPO (5B8), CD14 (M5E2), CD33 (WM54), CD56 (B159), CD38 (HIT2), CD138 (Mi15), Kappa (G20-193), Lambda (JDC-12) and all T-cell markers were negative. As the blasts expressed positivity for highly specific B lineage marker (cytoCD22) and negativity for highly specific myeloid lineage marker (cytoMPO) on immunophenotyping, all the morphological differentials were ruled out and the diagnosis of precursor B cell ALL was established. The possibility of biphenotypic acute leukemia (BAL) was ruled out as WHO modification of EGIL's criteria for the diagnosis of BAL were not fulfilled.  The patient was treated with induction chemotherapy including Vincristine, L'asparaginase, and Prednisolone. Central nervous system prophylaxis with two doses of intrathecal Methotrexate was also given. The patient tolerated the chemotherapy well. The post induction bone marrow was in morphological remission.
Granular ALL accounts for 2 to 7% of childhood lymphoblastic leukemias but is extremely rare in adults. , The criterion for diagnosis of granular ALL is more than 1% of lymphoblasts having at least three or more clearly defined azurophilic granules. However, the majority of granular ALL often show more than 5% of lymphoblasts with small numbers of distinctive azurophilic granules.  The majority of granular ALL patients have precursor B-cell phenotype, however, rare cases of precursor T-cell ALL have also been reported. , According to published literature, on electron microscopic studies these cytoplasmic granules ultrastructurally resemble multivesicular bodies or Gall Bodies. 
Few azurophilic granules are normally seen in a small percentage of lymphocytes recognized as large granular lymphocytes (LGL). The leukemia arising from these lymphocytes is called as large granular lymphocytic (LGL) leukemia.  The granules of granular ALL  are much larger than those seen in the LGL leukemia, hence can be easily differentiated. However, these granules are similar to those present in the myeloid cells which may lead to misdiagnosis of acute myeloid leukemia and the hypergranular blasts may mimic the abnormal promyelocytes of APML. These granules may be positive for Sudan Black B (SBB), which is usually positive in myeloid leukemia, acid phosphatase or PAS staining. Such unusual positivity of SBB further adds to diagnostic difficulties. , However, the MPO has never been reported to be positive in granular ALL. In the present case, the blasts were large with moderate to abundant basophilic cytoplasm, with numerous azurophilic granules which were negative for MPO and were positive for NSE.
It is known that NSE positivity may be present in lymphoblasts.  Hence, in such problematic cases immunophenotype analysis by flow cytometry or immunohistochemistry plays an important role for lineage determination. ,, However some flow cytometry laboratories use a panel of limited antibodies for immunophenotypic analysis of acute leukemia based on the morphology.  This may lead to erroneous or inconclusive results leading to further delay in arriving at the correct diagnosis and treatment.
Amongst all published cases of granular ALL, to our knowledge, only two cases of hypergranular B-cell ALL have been reported.  In these two cases the granules were positive for the PAS reaction and on immunophenotyping blasts were positive for CD45, CD10 and CD19.  In the index case, the blasts were positive for CD10, CD19, cytoplasmic-CD22, HLADR, and CD34 and also expressed CD13 and CD117, however, negative for cytoplasmic-MPO.
In conclusion, the use of correct cytochemical stains like myeloperoxidase and immunophenotypic analysis using a comprehensive antibody panel can avoid the diagnostic confusions. Though childhood granular ALL does not bear any prognostic significance, it is important to diagnose this entity as it is a poor prognostic factor in adult patients. ,
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