Acute Myeloid Leukemias (AML)
AML with t (8;21) (q22;q22), (AML1/ETO)
Blasts express CD34, HLA-DR, CD13, CD33, CD15, MPO, and CD117. CD19 is often expressed.
AML with t (8;21) is usually associated with good response to chemotherapy and high rate of complete remission with long-term disease-free survival.
AML with inv (16) (p13;q22) or t (16;16) (p13;q22), (CBFβ/MYH11)
Blasts express CD13, CD33, MPO, CD117, as well as CD14, CD4, CD11b, CD11c, CD64, and CD36.
AML with inv (16) or t (16;16) typically shows myeloid and monocytic differentiation and the presence of eosinophilia, referred to as AMML-Eo. The disease usually responds well to chemotherapy with high rate of complete remission.
AML with t (15;17) (q22;q12), (PML/RARα) and variants
Leukemic cells express CD13, CD33, MPO, and CD117, but not CD34 and HLA-DR.
AML with t (15;17), known as acute promyelocytic leukemia (APL), is sensitive to all-trans retinoic acid (ATRA) treatment. APL is frequently associated with DIC.
AML with t(9;11)(p22;q23), (MLLT3/MLL)
Leukemic cells variably express HLA-DR, CD33, CD117, MPO, and monocytic markers (CD4, CD14, CD11b, CD11c, CD64, and lysozyme). CD34 is often absent.
AML with 11q23 (MLL) abnormalities is usually associated with monocytic features. AML with 11q23 abnormalities has an intermediate survival.
AML with t(6;9)(p23;q34) (DEK/NUP214)
Blasts often express MPO, CD13, CD33, HLA-DR, CD117, CD34, and CD15. Some cases also express CD64 or TdT.
AML with t(6;9) may have monocytic features, and is often associated with basophilia and multilineage dysplasia. Disease in both adults and children has a poor prognosis.
AML with inv(3)(q21q26) or t(3;3)(q21;q26), (RPN1/EVI1)
Blasts often express CD13, CD33, HLA-DR, CD34. Some case may also express CD7 (aberrant), CD41 or CD61.
AML with inv(3) or t(3;3) is an aggressive disease with poor prognosis.
AML with t(1;22)(p13;q13) (RBM15/MKL1) (megakaryocytic)
Blasts often express CD41, CD61, CD36, and may also express CD13 and CD33.
Disease most commonly occurs in infants without Down syndrome. Outcome is generally poor, but may respond to intensive chemotherapy with long survival.
AML with myelodysplasia-related changes
Blasts often express CD34, HLA-DR, CD13, CD33, MPO, CD117. Aberrant expression of Cd7 and/or CD56 may occur.
AML with myelodysplasia-related changes including AML arising from prior MDS or MDS/MPN, AML with an MDS-related cytogenetic abnormality, and AML with multilineage dysplasia. The disease has poor prognosis with low rate of achieving remission.
AML, therapy-related (t-AML)
Alkylating agent/radiation related: Blasts express CD34, HLA-DR, CD13, CD33, MPO, and CD117.
Topoisomerase II inhibitor related: Same as AML with 11q23 abnormalities.
Alkylating agent/radiation related AML is generally refractory to chemotherapy and is associated with short survival.
Topoisomerase II inhibitor-related AML often show monocytic differentiation.
Therapy-related myelodysplastic syndrome (t-MDS) has similar prognosis as t-AML.
AML, minimally differentiated (also known as AML-M0)
Blasts express CD13, CD33, CD117, CD34, HLA-DR, but not MPO.
Flow cytometric immunophenotyping is required for the confirmation of myeloid differentiation.
AML without maturation (also known as AML-M1)
Blasts express CD13, CD33, CD117, and MPO. CD34 is often positive.
Blasts constitute >90% of the nonerythroid nucleated cells in the marrow, and at least 3% of the blasts are positive for MPO.
AML with maturation (also known as AML-M2)
Blasts express CD13, CD33, CD15, CD117, and MPO. CD34 and HLA-DR are often positive.
Blasts constitute 20–89% of nonerythroid cells, and monocytes comprise <20% of the bone marrow cells.
Acute myelomonocytic leukemia (also known as AML-M4)
Leukemic cells variably express CD13, CD33, CD117, HLA-DR, CD14, CD4, CD11b, CD11c, and CD64. CD34 may be positive.
Monocytic component (monoblasts to monocytes) comprises 20–79% of bone marrow cells.
Acute monoblastic/monocytic leukemia (also known as AML-M5)
Leukemic cells variably express CD13, CD33, CD117, HLA-DR, CD14, CD4, CD11b, CD11c, CD64, and CD68. CD34 is typically negative.
Monocytic component (monoblasts to monocytes) comprises >80% of bone marrow cells.
Acute erythroid leukemia (also known as AML-M6) and pure erythroid leukemia
Erythroblasts generally lack myeloid markers, but are positive for CD36 and glycophorin A (CD235). Myeloblasts express CD13, CD33, CD117, and MPO with or without CD34 and HLA-DR. The erythroid cells in pure erythroid leukemia express CD36 and glycophorin A with the more immature forms expressing CD34 and HLA-DR.
The diagnostic criteria for acute erythroid leukemia: erythroblasts constitute >50% of the marrow cells, and myeloblasts comprise >20% of the nonerythroid cells.
Pure erythroid leukemia is a neoplastic proliferation of erythroid precursors (>80% of nucleated marrow cells) without a significant myeloblastic component.
Acute megakaryocytic leukemia (known as AML-M7)
Blasts express one or more of the platelet glycoproteins (CD41, CD61, CD42), and variably express HLA-DR, CD34, CD117, CD13, and CD33.
Flow cytometric immunophenotyping is required for confirmation of megakaryocytic differentiation.
Blastic plasmacytoid dendritic cell neoplasm (formerly known as blastic NK-cell lymphoma)
Neoplastic cells express CD4, CD43, CD45RA, CD56, and plasmacytoid dendritic cell-associated antigens CD123, CD303, TCL1. May also express CD68 and TdT.
The disease is also called agranular CD4+/CD56+ hematodermic tumor. Besides marrow involvement, skin lesions are present. The disease is aggressive with short survival.
Acute leukemia of ambiguous lineage
Undifferentiated acute leukemia: Blasts express HLA-DR, CD34, CD38, and may express TdT, but lack lineage-specific markers such as CD79a, CD22, strong CD19, IgM, CD3, and MPO.
Bilineal acute leukemia: There is a dual population of blasts with each population expressing markers of a distinct lineage, such as myeloid and lymphoid, or B and T.
Biphenotypic acute leukemia: The blasts co-express myeloid and T or B lineage-specific antigens, or concurrent B and T antigens.
Cases of bilineal and biphenotypic acute leukemia usually present with cytogenetic abnormalities. The common abnormalities include Philadelphia chromosome, t (4;11)(q 21;q 23) or other 11q23 abnormalities. The prognosis of acute leukemia of ambiguous lineage is poor.
Acute Lymphoblastic Leukemias/Lymphomas (ALL/LBL)
Precursor B-lymphoblastic leukemia/lymphoblastic lymphoma (B-ALL/LBL) (also known as B-cell acute lymphoblastic leukemia)
Early precursor B-ALL/LBL:
TdT+, HLA-DR+, CD34(−/+), CD10–, CD45(−/+), CD19+, cCD22+, CD20–, CD15+, cIg–, sIg–.
TdT+, HLA-DR+, CD34+, CD10+, CD45+(weak), CD19+, CD20+, cIg–, sIg–.
TdT(−/+), CD34(−/+), HLA-DR+, CD45+(weak), CD19+, CD20+, cIgM+, sIg–.
Cytogenetic abnormalities in B-ALL/LBL include several groups: hypodiploid, low hyperdiploid (<50), high hyperdiploid (>50), translocations, and pseudodiploid. The commonly seen translocations include t (9;22), t (12;21), t (5;14), t (1;19), t (17;19), t (4;11), and other translocations involving 11q23. The cytogenetic findings are prognostically important.
Precursor T-lymphoblastic leukemia/lymphoblastic lymphoma (T-ALL/LBL)
T-ALL/LBL often has an immunophenotype that corresponds to the common thymocyte stage of differentiation. The blasts are positive for TdT and often CD10, and variably express CD1a, CD2, CD3, CD4, CD5, CD7, and CD8. CD4 and CD8 are frequently co-expressed on the blasts.
Some T-ALL/LBL has an immunophenotype that corresponds to prothymocyte stage of differentiation. The blasts are negative for both CD4 and CD8.
In about one-third of T-ALL/LBL translocations have been detected involving the α and δ T-cell receptor (TCR) loci at 14q11.2, the β locus at 7q35, and the γ locus at 7p14-15, with a variety of partner genes.
T-ALL/LBL can be part of a unique disease entity known as the 8p11 myeloproliferative syndrome caused by constitutive activation of FGFR1. The disease is characterized by chronic myeloproliferative disorder that frequently presents with eosinophilia and associated T-cell lymphoblastic lymphoma.
Mature B-cell Neoplasms
Chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL)
Lymphoma cells are light chain restricted and express CD5, CD19, CD20 (weak), CD22 (weak), CD79a, CD23, CD43, and are negative for CD10, Bcl-1 (cyclin D1), and FMC-7. A subset of cases expresses CD11c (weak). Cases with unmutated Ig variable region genes have been reported to be positive for CD38 and ZAP-70.
The clinical course is often indolent but incurable. The disease may progress/transform to prolymphocytic leukemia (PLL) or large B-cell lymphoma (Richter syndrome). CD38 and/or ZAP-70 positivity is associated with worse prognosis, and both have been used as prognostic markers for the disease.
Trisomy 12 is reported in ~20% of cases, and deletions at 13q14 in up to 50% of cases. Trisomy 12 in CLL/SLL correlates with a worse prognosis.
B-cell prolymphocytic leukemia (B-PLL)
The cells of B-PLL strongly express surface IgM and B-cell antigens CD19, CD20, CD22, CD79a, CD79b, and FMC-7. CD5 is present in about one-third of cases and CD23 is typically negative.
B-PLL can be divided into CD5+ B-PLL (arising in CLL/SLL) and CD5– B-PLL (de novo PLL). CD5+ B-PLL has a longer median survival than CD5– B-PLL.
Lymphoplasmacytic lymphoma/Waldenström macroglobulinemia (LPL)
The cells express strong surface immunoglobulin, usually of IgM type, and express B-cell antigens (CD19, CD20, CD22, CD79a) and are CD5–, CD10–, CD23–, CD43±, and CD38+. Lack of CD5 and strong immunoglobulin expression are useful in distinction from CLL/SLL.
Characteristic features include IgM monoclonal gammopathy; spectrum of small lymphocytes, plasmacytoid lymphocytes, and plasma cells; interstitial, nodular, or diffuse pattern of bone marrow involvement; and typical immunophenotype (sIgM+, CD19+, CD20+, CD5–, CD23–, CD10–).
Splenic marginal zone lymphoma (SMZL)
The tumor cells express surface IgM, and are positive for CD19, CD20, CD79a, and negative for CD5, CD10, CD23, CD25, CD43, CD103, and Bcl-1 (cyclin D1).
Circulating lymphoma cells are usually characterized by the presence of short polar villi (villous lymphocytes). The clinical course is indolent, but the disease is incurable.
Hairy cell leukemia (HCL)
Leukemic cells express surface immunoglobulin, B-cell markers (CD19, CD20, CD22, CD79a), and are often positive for CD11c, CD25, FMC-7, and CD103, but negative for CD5, CD10, and CD23.
Patients often present with splenomegaly, pancytopenia (monocytopenia is characteristic), and may have circulating hairy leukemic cells. Bone marrow reticulin fibers are characteristically increased, resulting in "dry tap" during aspirate procedure. Interferon-alpha, deoxycoformycin (pentostatin), or 2-chlorodeoxyadenosine (2-CdA, cladribine) can induce long-term remissions.
Plasma cell myeloma/plasmacytoma
The malignant cells express monoclonal cytoplasmic immunoglobulin, lack CD45 and pan-B cell antigens (CD19, CD20, CD22), but CD79 is often positive. The cells are typically positive for CD38, CD138, and often express CD56, CD43, and rarely CD10. The phenotype of plasma cell leukemia is similar to that of myeloma, but CD56 is negative.
Plasma cells do not express surface immunoglobulin. For clonality (or light chain restriction) determination by flow cytometry analysis, cell permeabilization procedure is necessary. The procedure gives antibodies access to intracellular structures/molecules.
Extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma)
Lymphoma cells typically express surface immunoglobulin with light chain restriction. The cells are positive for CD19, CD20, CD79a, CD43, and negative for CD5, CD10, CD23, and Bcl-1.
Trisomy 3 is found in ~60% and t (11;18) (q21;q21) has been detected in 25–50% of MALT lymphoma cases. Neither t (14;18) nor t (11;14) is present. Cases with t (11;18) appear to be resistant to H. pylori eradication therapy.
Nodal marginal zone B-cell lymphoma (NMZL)
The immunophenotype of most cases is similar to that of extranodal MALT lymphoma.
NMZL is a primary nodal B-cell neoplasm that morphologically resembles lymph nodes involved by marginal zone lymphomas of extranodal or splenic types, but without evidence of extranodal or splenic disease.
Follicular lymphoma (FL)
Lymphoma cells are usually positive for pan–B-cell antigens (CD19, CD20), surface immunoglobulin, CD10, Bcl-2, Bcl-6, and negative for CD5. Bcl-2 is expressed in the majority of cases, ranging from nearly 100% in grade 1 to 75% in grade 3 FL.
All cases have cytogenetic abnormalities. The t (14;18) (q32;q21) translocation, involving rearrangement of the Bcl-2 gene and IgH gene, is present in 80–95% of FL. FL may transform into high-grade B-cell lymphoma with features intermediate between DLBCL and Burkitt lymphoma, and c-myc (8q24) rearrangement is often involved. Bcl-2 is useful in distinguishing reactive follicular hyperplasia (Bcl-2 negative) and FL (Bcl-2-positive).
Mantle cell lymphoma (MCL)
Lymphoma cells express surface immunoglobulin, pan–B-cell antigens (CD19, CD20), Bcl-1, FMC-7, CD5, CD43, and are typically negative for CD10, CD23, and Bcl-6.
MCL and CLL/SLL are the two common CD5-positive B-cell lymphoproliferative disorders. But unlike CLL/SLL, MCL cells express bright surface immunoglobulin, bright CD20 and FMC-7, and are CD23 negative. Virtually all cases express Bcl-1 (cyclin D1) due to gene rearrangement.
Diffuse large B-cell lymphoma (DLBCL)
DLBCL cells typically express various pan–B-cell antigens (CD19, CD20, CD22, CD79a), surface and/or cytoplasmic immunoglobulin with light chain restriction, Bcl-6, and CD10. Bcl-2 is positive in 30–50% of cases.
Morphologic variants of DLBCL include centroblastic, immunoblastic, T-cell/histiocyte rich, anaplastic, and plasmablastic DLBCL. Bcl-2 expression has been reported to be associated with an adverse disease-free survival, while expression of Bcl-6 appears to be associated with a better prognosis.
Mediastinal (thymic) large B-cell lymphoma (Med-DLBCL)
Lymphoma cells express CD45 and B-cell antigen (CD19, CD20). Immunoglobulin and HLA-DR are often absent. The cells do not express CD5 and CD10, and lack Bcl-2, Bcl-6, and c-myc rearrangements.
Med-DLBCL is a subtype of DLBCL arising in the mediastinum of putative thymic B-cell origin with distinct clinical, immunophenotypic, and genotypic features. Tissue sections usually show diffuse lymphoid proliferation, compartmentalized into groups by fine/delicate fibrotic bands.
Intravascular large B-cell lymphoma
Lymphoma cells express pan–B-cell antigens (CD19, CD20).
The disease is a rare subtype of extranodal DLBCL characterized by the presence of lymphoma cells only in the lumina of small vessels, particularly capillaries. Brain and skin are the common sites of involvement.
Primary effusion lymphoma (PEL)
Lymphoma cells express CD45, but are usually negative for pan–B-cell markers (CD19, CD20). Surface and cytoplasmic immunoglobulin is often absent. Activation and plasma cell-related markers such as CD30, CD38, and CD138 are usually positive.
PEL is a neoplasm of large B cells usually presenting as serous effusions without detectable tumor masses. It is universally associated with human herpes virus 8 (HHV-8), most often occurring in the setting of immunodeficiency.
Lymphomatoid granulomatosis (LYG)
Lymphoma cells express CD20, and are variably positive for CD30, but negative for CD15. The cells lack immunoglobulin expression. The background small lymphocytes are CD3–positive T cells.
LYG is an angiocentric and angiodestructive lymphoproliferative disease involving extranodal sites, composed of Epstein-Barr virus (EBV)-positive B cells admixed with reactive T cells, which usually numerically predominate. LYG may progress to an EBV-positive DLBCL. The common sites of involvement are lung, kidney, brain, liver, and skin.
Burkitt lymphoma (BL)
Lymphoma cells express surface immunoglobulin with light chain restriction, pan–B-cell antigens (CD19, CD20), CD10, and Bcl-6. The cells are negative for CD5, CD23, CD34, and TdT. Nearly 100% of the cells are positive for Ki-67, a proliferation marker.
All BL cases show a translocation of c-myc gene at chromosome 8q24 to the IgH gene at 14q32 or less commonly to light chain loci at 2p12 or 22q11. Genetic abnormalities involving the c-myc gene play an essential role in BL pathogenesis. The expression of CD10 and Bcl-6 indicates a germinal center origin of the tumor cells. BL is highly aggressive but potentially curable.
Mature T-cell and NK-cell Neoplasms
T-cell prolymphocytic leukemia (T-PLL)
Leukemic cells express CD2, CD3, CD7, but not TdT and CD1a. The cells can be CD4+/CD8−(60%), CD4+/CD8+ (25%), or CD4−/CD8+ (15%).
T-PLL is an aggressive T-cell leukemia characterized by the proliferation of small to medium sized prolymphocytes with a mature post-thymic T-cell phenotype involving the blood, bone marrow, lymph nodes, spleen, and skin.
T-cell large granular lymphocyte leukemia (T-LGL)
T-LGL cells have a mature T-cell immunophenotype. Approximately 80% of cases are CD3+, TCR α β+, CD4–, and CD8+.
T-LGL is a heterogeneous disorder characterized by a persistent (>6 months) increase in peripheral blood large granular lymphocytes (LGLs), without a clearly identified cause. Severe neutropenia with or without anemia is a characteristic clinical feature. Pure red cell hypoplasia has been reported in association with T-LGL leukemia. Splenomegaly, rheumatoid arthritis, and the presence of autoantibodies are commonly seen in patients with T-LGL.
Aggressive NK-cell leukemia
Leukemic cells are CD2+, surface CD3–, cytoplasmic CD3ε+, CD56+, and positive for cytotoxic molecules (TIA-1, granzyme B, and/or perforin). This immunophenotype is identical to that of extranodal NK/T-cell lymphoma, nasal type.
Aggressive NK-cell leukemia is characterized by a systemic proliferation of NK cells. The disease has an aggressive clinical course. T-cell receptor (TCR) genes are in germline configuration.
Adult T-cell leukemia/lymphoma (ATLL)
Tumor cells express T-cell antigens (CD2, CD3, CD5), but usually lack CD7. Most cases are CD4+, CD8–. Rare cases are CD4–, CD8+, or double negative for CD4 and CD8. CD25 is expressed in virtually all cases.
ATLL is a peripheral T-cell neoplasm most often composed of highly pleomorphic lymphoid cells. The disease is usually widely disseminated, and is caused by the human T-cell leukemia virus type 1 (HTLV-1). ATLL is endemic in Japan, the Caribbean basin, and parts of Central Africa.
Extranodal NK/T-cell lymphoma, nasal type
The typical immunophenotype is CD2+, CD56+, surface CD3–, and cytoplasmic CD3 ε+. Most cases are positive for cytotoxic molecules (TIA-1, granzyme B, perforin).
The disease entity is designated NK/T (rather than NK) cell lymphoma because while most cases appear to be NK-cell neoplasms (EBV+, CD56+), rare cases show an EBV+, CD56– cytotoxic T-cell phenotype. T-cell receptor and immunoglobulin genes are in germline configuration in a majority of cases. EBV can be demonstrated in the tumor cells in nearly all cases. The prognosis is variable.
Enteropathy-type T-cell lymphoma
Tumor cells are CD3+, CD5–, CD7+, CD8∓, CD4–, CD103+, and contain cytotoxic molecules.
The tumor occurs most commonly in the jejunum or ileum, and there is a clear association with celiac disease. The prognosis is usually poor.
Hepatosplenic T-cell lymphoma
Tumor cells are CD3+, CD4–, CD8–, CD5–, CD56±. The cells are usually TCR γδ + and TCR α β–.
Hepatosplenic T-cell lymphoma is an extranodal and systemic neoplasm derived from cytotoxic T cells usually of γδ T-cell receptor type, demonstrating marked sinusoidal infiltration of spleen, liver, and bone marrow. The clinical course is aggressive.
Subcutaneous panniculitis-like T-cell lymphoma (SPTCL)
Tumor cells are usually CD3+, TCR α β +, CD5–, CD4–, CD8–, and express cytotoxic molecules.
SPTCL is a cytotoxic T-cell lymphoma, which preferentially infiltrates subcutaneous tissue. Some patients may present with a hemophagocytic syndrome with pancytopenia. The clinical course is aggressive.
Mycosis fungoides and Sézary syndrome (MF/SS)
The typical phenotype is CD2+, CD3+, TCR β +, CD5+, CD4+/CD8– (rarely CD4–/CD8+). Virtually all cases are negative for CD26 (a marker for treatment monitoring). CD7 is usually negative.
MF is a mature T-cell lymphoma, presenting in the skin with patches/plaques and characterized by epidermal and dermal infiltration of small to medium-sized T cells with cerebriform nuclei. SS is a generalized mature T-cell lymphoma characterized by the presence of erythroderma, lymphadenopathy, and neoplastic T lymphocytes in the blood.
Primary cutaneous CD30– positive T-cell lymphoproliferative disorders
Primary cutaneous anaplastic large cell lymphoma (C-ALCL):
Tumors cells express T-cell antigens (CD2, CD3, CD5, CD7) and are usually positive for CD4. CD30 is expressed in >75% of the cells. Aberrant T-cell phenotype with loss of one or more T-cell antigens is common.
Lymphomatoid papulosis (LyP):
The atypical T cells are CD4+, CD8–. The cells often express aberrant phenotypes with variable loss of pan–T-cell antigens (eg, CD2, CD5, or CD7). CD30 is positive in a LyP subtype (type A).
LyP and C-ALCL constitute a spectrum of related conditions originating from transformed or activated CD30-positive T lymphocytes. They may coexist in individual patients, they can be clonally related and they often show overlapping clinical and/or histologic features.
Angioimmunoblastic T-cell lymphoma (AITL)
Neoplastic cells express T cell antigens (CD2, CD3, CD5, CD7), usually without aberrant antigen loss, and are CD4+ and CD8–. The neoplastic T cells are positive for CD10 and/or Bcl-6. CD21 stain highlights the intact or disrupted follicular dendritic meshwork.
AITL is a T-cell lymphoma characterized by systemic disease and a polymorphous infiltrate involving lymph nodes. TCR genes are rearranged in the majority (>75%) of cases. Secondary EBV-related B-cell lymphoma may occur. Almost all cases are positive for CD10 and/or Bcl-6, suggesting a germinal center derivation of the tumor cells. The clinical course is very aggressive.
Peripheral T-cell lymphoma, unspecified
Neoplastic cells express T cell antigens (CD2, CD3, CD5, CD7), but aberrant T-cell pheno-types with antigen loss are frequent. Most nodal cases are CD4+, CD8–, CD30, and CD56 may be positive.
The diseases are among the most aggressive of the non-Hodgkin lymphomas.
Anaplastic large cell lymphoma (ALCL)
The tumor cells express one or more T-cell antigens (CD2, CD3, CD5, CD7). The cells usually express CD30 (membrane and in the Golgi region), ALK (cytoplasmic and/or nuclear), EMA, cytotoxic molecules, CD43, and CD45.
Expression of ALK in ALCL is due to genetic alteration of the ALK locus on chromosome 2. The most common alteration is t(2;5)(p23;q35), resulting in fusion of the ALK gene and nucleophosmin (NPM) gene on 5q35. ALK-positive ALCL has a favorable prognosis.