Immunoreactivity of MIC2 (CD99) and terminal deoxynucleotidyl transferase in bone marrow clot and core specimens of acute myeloid leukemias and myelodysplastic syndromes

Division of Hematopathology, Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC 27599-7525, USA.
Archives of pathology & laboratory medicine (Impact Factor: 2.84). 03/2006; 130(2):153-7. DOI: 10.1043/1543-2165(2006)130[153:IOMCAT]2.0.CO;2
Source: PubMed


MIC2 ("thymus leukemia") antigen has been shown to be expressed by T cells and monocytes, as well as B cells and granulocyte-lineage cells. It is most intensely expressed by the most immature thymus T-lineage cells and is more intensely expressed by CD34-positive/CD33-positive myeloid cells (compared to more mature myeloid cells) and the earliest CD34-positive/CD10-positive B-cell precursor cells (compared to cells of later B-cell precursor stages). CD99 (MIC2) is characteristically expressed in precursor B- and T-cell lymphoblastic lymphomas/leukemias, as well as in Ewing sarcoma/primitive neuroectodermal tumors (ES/PNET). It has also been shown to be expressed in a few terminal deoxynucleotidyl transferase (TdT)-positive myeloid processes, but has been uniformly negative in TdT-negative myeloid processes. A more recent study showed that 43% of acute myeloid leukemias (AMLs) and 55% of chloromas express CD99, concluding that CD99 is commonly expressed in AML and rarely seen in myeloproliferative disorders, myelodysplastic syndromes, or normal bone marrow. Although this study speculated that MIC2 expression was probably not limited to TdT-positive AML, there was no comparison with TdT reactivity in this study.
Since AML and high-grade myelodysplastic syndrome may occasionally be difficult to distinguish morphologically from acute lymphoblastic leukemia and ES/ PNET, we undertook a study to analyze MIC2 expression in conjunction with TdT reactivity in distinguishing AML or high-grade myelodysplastic syndrome from acute lymphoblastic leukemia and ES/PNET.
We studied bone marrow core and clot paraffin specimens from AML (classified according to criteria of the World Health Organization; n = 49), myelodysplastic syndromes (n = 4), precursor B-cell acute lymphoblastic leukemia (n = 4), ES/PNET (n = 1), and normal bone marrow (n = 3) with MIC2 (CD99) and TdT immunohistochemistry.
Overall, CD99 was expressed in 24 (49%) of 49 AML cases, including all (11/11) TdT-positive cases. CD99 was expressed in all subtypes of AML except M5. Myelodysplastic syndromes and normal bone marrow specimens were uniformly CD99 negative. Expression of TdT was limited to a subset of AML-M0, -M1, -M2, and -M4, and AML with multilineage dysplasia.
In contrast to a previous study, CD99 expression was not restricted to TdT-positive hematologic proliferations. In particular, the CD99-positive M3 and M7 AMLs were TdT negative. An M5 AML may likely be excluded based on a uniform TdT-negative/CD99-negative immunophenotype. In addition, in our experience, CD99 should be routinely evaluated on bone marrow clots, owing to decreased reactivity or loss of reactivity in rapid decalcifying (RDO) solution-decalcified specimens.

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    • "These results had the potential to be misdiagnosed as Ewing's sarcoma/PNET because CD99 is a transmembrane glycoprotein p30/32mic2, a product of the MIC2 gene, and is positive in Ewing's sarcoma/PNET and lymphoblastic lymphoma.14 However, CD99 has also been expressed by monocytes, B cells, and granulocyte-lineage cells such as those from myeloid sarcoma, lymphoblastic lymphoma, or TdT-positive AML.15 Immunoreactivity for CD99 has been reported in more than 50% of the myeloid sarcomas, which is in line with its not infrequent expression in hematopoietic tumors.5,11-14 TdT is expressed in approximately 90% of acute lymphoblastic lymphoma cases, which represents a small subset of AML cases. "
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    ABSTRACT: Myeloid sarcoma is a rare extramedullary myeloid tumor, which is frequently misdiagnosed when no evidence of leukemia is initially observed. Here, we report on a peculiar case of a 49-year-old man afflicted with multiple masses in the jejunum, the superior mesentery, and the serosa of the transverse colon, without leukemic manifestation. The tumor was composed of undifferentiated small round cells containing eosinophilic cytoplasm, which were negative for myeloperoxidase, nonspecific esterase, lysozyme, terminal deoxynucleotidyl transferase, leukocyte common antigen, CD3, CD4, CD15, CD20, CD30, CD43, CD56, CD68/PG-M1, CD79a, human melanoma black-45, c-kit, and CD34 with positivity only for CD68/KP1, CD99, and vimentin. Under electron microscopy, those cells had abundant membrane-bound cytoplasmic granules that measured 200 to 300 nm in diameter, which were consistent with granulocytic azurophilic granules. The tumor was finally diagnosed as a myeloid sarcoma. The presence of non-leukemic myeloid sarcomas showing immunonegativity for conventional myeloid-leukemic markers necessitated a diagnosis by ultrastructural observation.
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    • "Lymphoblastic processes are also in the differential diagnosis and like AML, myeloid sarcomas also frequently express TdT (Lewis et al., 2007). In fact, a study by Kang and Dunphy (2006) "
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    ABSTRACT: Myeloid sarcomas are extramedullary lesions composed of myeloid lineage blasts that typically form tumorous masses and may precede, follow, or occur in the absence of systemic acute myeloid leukemia. They most commonly involve the skin and soft tissues, lymph nodes, and gastrointestinal tract and are particularly challenging to diagnose in patients without an antecedent history of acute myeloid leukemia. We conducted a search of the English language medical literature for recent studies of interest to individuals involved in the diagnosis of myeloid sarcoma. The differential diagnosis includes non-Hodgkin lymphoma, blastic plasmacytoid dendritic cell neoplasm, histiocytic sarcoma, melanoma, carcinoma, and (in children) small round blue cell tumors. The sensitivity and specificity of immunohistochemical markers must be considered when evaluating a suspected case of myeloid sarcoma. A high percentage of tested cases have cytogenetic abnormalities. A minimal panel of immunohistochemical markers should include anti-CD43 or anti-lysozyme as a lack of immunoreactivity for either of these sensitive markers would be inconsistent with a diagnosis of myeloid sarcoma. Use of more specific markers of myeloid disease, such as CD33, myeloperoxidase, CD34 and CD117 is necessary to establish the diagnosis. Other antibodies may be added depending on the differential diagnosis. Identification of acute myeloid leukemia-associated genetic lesions may be helpful in arriving at the correct diagnosis.
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    • "Cytological assessment of the CD117 + population and correlation with ret40f immunostained sections is essential to make these distinctions. Other antibodies that can be used for quantification of myeloid precursors include CD99 (mic2) and Tdt (Kang & Dunphy, 2006). It should be noted that, among the blastic population, there can be heterogeneity in the intensity of expression of some of these antigens like CD34 in some cases. "
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    ABSTRACT: Acute myeloid leukaemia (AML) with multilineage dysplasia (MD) is one of the four main categories of AML in the World Health Organization (WHO) classification. The role of bone marrow trephine biopsy (BMTB) histology and immunohistochemistry in the diagnosis of AML-MD is currently unclear. BMTBs were studied in 11 cases of AML-MD and two cases of myelodysplasia that subsequently transformed to AML. Among them, six cases showed trilineage dysplasia and seven showed bilineage dysplasia. With respect to conforming to the WHO definition of AML, documentation of an increased proportion of immature myeloid cells was possible on morphology and counting of immature cells following immunostaining with CD34, CD117 or HLA-DR antibodies. Recognition and quantification of dysplastic features in the haemopoietic lineages was made easier by immunohistochemistry with antibodies to ret40f (glycophorin C), myeloperoxidase, CD61 and/or CD42b, CD34, CD117 and HLA-DR. Based on this relatively small series of cases we show the utility of BMTB and immunohistochemistry as an aid to the diagnosis of AML-MD. This has to be seen not just in light of its utility at diagnosis, but also the role the diagnostic BMTB would play for purposes of comparison when follow-up BMTBs are submitted in this group of patients.
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