Langerhans cell histiocytosis in acute leukemias of ambiguous or myeloid lineage in adult patients: support for a possible clonal relationship.

Four patients presented with acute leukemia of ambiguous or myeloid lineage in association with Langerhans cell histiocytosis and provide evidence suggesting a common origin of the two neoplasms. One patient had a non-constitutional trisomy 21 in both the leukemic blasts and the Langerhans cells indicative of a clonal relationship. A second case expressed CD2, CD13, and CD117 on both the Langerhans cells and the blasts suggesting a possible clonal relationship. All four cases exhibited geographic intermingling of the Langerhans cell histiocytosis and acute leukemia and shared unique features including extramedullary leukemia involving lymph nodes in all cases with Langerhans cell histiocytosis only present in sites involved by acute leukemia. T-cell antigen expression was present in all cases with one meeting criteria for mixed phenotype acute leukemia, T/myeloid, not otherwise specified. These findings support the concept that coexistent Langerhans cell histiocytosis and acute leukemia is clonally related in some cases. Furthermore, these cases of acute myeloid or acute leukemia of ambiguous lineage with Langerhans cell histiocytosis share some unique features suggesting a common underlying neoplastic hematopoietic stem cell.

Anaplastic large cell lymphoma: a flow cytometric analysis of 29 cases.

We report our experience with flow cytometric (FC) analysis of 29 cases of anaplastic large cell lymphoma (ALCL). Morphologic analysis of processed cytocentrifuged preparations demonstrated neoplastic cells in 28 cases. In 25 of these, an aberrant lymphoid population was detected by FC analysis. The majority showed high orthogonal light scatter, similar to monocytes or granulocytes. Of the antigens CD2, CD3, CD4, CD5, and CD7, 5 cases expressed 1, 8 expressed 2, 6 expressed 3, 3 expressed 4, and 3 expressed all 5. CD4 was expressed most commonly (20/25 [80%]), followed by CD2 (18/25 [72%]), CD3 (10/25 [40%]), and CD5 and CD7 (8/25 [32%] each). CD45 was expressed in 23 of 25 cases and CD13 in 7 of 9. Of 21 cases, 13 were anaplastic lymphoma kinase (ALK)+, all of which were CD4+, vs 5 of 8 ALK - cases (P = .042). Most ALCLs can be detected and characterized by multiparameter FC analysis. However, light scatter gating on typical lymphoid regions may yield false-negative results in a substantial number of cases.

CD5-positive B-cell neoplasms of indeterminate immunophenotype: a clinicopathologic analysis of 26 cases.

The flow cytometric classification of CD5-positive small B-cell neoplasms is dependent largely on the differential expression of CD23 and FMC-7. Occasional CD5-positive neoplasms with prominent co-expression of these antigens are encountered, precluding definitive immunophenotypic classification. The authors studied the clinicopathologic features of 26 neoplasms with this indeterminate immunophenotype. Available morphologic material was reviewed and analysis of CYCLIN D1 derangement was performed in selected cases by a combination of immunohistochemical, molecular, and cytogenetic techniques. Individual neoplasms were classified based on correlation of morphologic features and results of CYCLIN D1 studies. The neoplasms were classified into five categories: chronic lymphocytic leukemia (14 cases), "favor chronic lymphocytic leukemia" (3 cases), mantle cell lymphoma (3 cases), lymphoplasmacytic lymphoma (1 case), and unclassifiable (5 cases). Three of the unclassifiable neoplasms had morphologic features of mantle cell lymphoma, but CYCLIN D1 derangement could not be demonstrated. Neither relative expression of CD23 and FMC-7 nor intensity of CD20 or surface immunoglobulin expression was helpful in final classification. The authors conclude that CD5-positive small B-cell neoplasms with an indeterminate immunophenotype are a heterogeneous group, requiring additional studies for final classification. The majority (65%) appear to be chronic lymphocytic leukemia, with most of the remaining cases either definitively mantle cell lymphoma or unclassifiable.

Characterization of incidentally identified minute clonal B-lymphocyte populations in peripheral blood and bone marrow.

We describe 69 patients in whom small clonal B-cell populations were detected incidentally in blood and bone marrow samples by flow cytometric studies. In 20 patients (29%), non-Hodgkin lymphoma (NHL) subsequently was diagnosed 0 to 40 months (median, 0.1 month) from initial flow cytometric studies. In 49 patients (71%), there was no evidence of NHL after 0.5 to 72 months (median, 16 months). Patients without overt NHL had a higher absolute WBC count than patients with NHL (2,260/microL vs 1,470/microL [2.26 vs 1.47 x 10(9)/L]; P < .01). Otherwise, there were no clinical or hematologic differences between the 2 groups. We identified 70 clonal populations in the 69 patients, ranging from 0.05% to 4.5% (median, 1.28%) of events. The mean percentage of clonal B cells was similar for the 2 groups. The populations were CD5-/CD10- in 34 cases; CD5+, chronic lymphocytic leukemia-like in 19; CD5+, indeterminate in 9; CD10+ in 3; hairy cell leukemia-like in 3; and CD5+, mantle cell lymphoma-like in 2. There were no immunophenotypic differences in patients with and without overt NHL.

Haematogones in the peripheral blood of adults: a four-colour flow cytometry study of 102 patients.

Haematogones have been extensively characterized in bone marrow, but not in the peripheral blood (PB). We studied 102 PB samples from adult patients with a sensitive flow cytometry method. Sixty-six of 102 samples (65%) contained detectable haematogones, ranging from 0.01% to 1.3% of white blood cells (median 0.06%, mean 0.13%). Of 66 cases with complete blood count data, 51 had absolute haematogone counts of 0.00037-0.105 x 10(9)/l (median 0.0054 x 10(9)/l, mean 0.012 x 10(9)/l). PB haematogones belonged exclusively to the most mature maturational stage. These findings have implications for PB analysis of minimal residual disease in acute lymphoblastic leukaemia and follicular lymphoma.

Immunophenotypic analysis of hematogones (B-lymphocyte precursors) and neoplastic lymphoblasts by 4-color flow cytometry.

Hematogones are identified by 4-color flow cytometry in most bone marrow specimens. They are more commonly found and are generally present in higher numbers in children. There is a general decline in hematogones with increasing age but a broad range exists at all ages and marrow from some adults contains relatively high numbers. They are often increased (> 5%) in regenerating marrow and in some clinical conditions, particularly various types of cytopenias and neoplastic diseases. Hematogones may morphologically resemble the neoplastic lymphoblasts of precursor B ALL and their immunophenotype also has features in common with neoplastic lymphoblasts. Distinguishing hematogones from neoplastic lymphoblasts may be problematic in post-chemotherapy and post-bone marrow transplant regenerating marrow. With 4-color flow cytometry using optimal antibody combinations the distinction can nearly always be made. Hematogone populations always exhibit a continuous and complete maturation spectrum of antigen expression typical of the normal evolution of B-lineage precursors; they lack aberrant or asynchronous antigen expression. The neoplastic lymphoblasts in precursor B ALL deviate from the normal B-lineage maturation spectrum and exhibit maturation arrest and over-, under-, and asynchronous expression of antigens observed on normal B-cell precursors and they often aberrantly express myeloid-associated antigens.

Comparison of immunophenotypes of small B-cell neoplasms in primary lymph node and concurrent blood or marrow samples.

Immunophenotyping of small B-cell neoplasms (SBCNs) may have a critical role in diagnosis. However, there are few data addressing whether the immunophenotypes of SBCNs in bone marrow (BM) and peripheral blood (PB) are representative of those in other tissue sites. We compared the immunophenotypic features of concurrently analyzed lymph node (LN) and BM/PB specimens using multiparameter flow cytometry. Fifty-five SBCNs were identified: 27 follicular lymphomas (FLs), 16 chronic lymphocytic leukemia/small lymphocytic lymphomas (CLL/SLLs), and 12 mantle cell lymphomas (MCLs). Major (presence vs absence) or minor (alteration of intensity) variations in expression of individual antigens between LN and BM/PB were observed in up to 25% of cases within a particular SBCN category. All FLs and CLL/SLLs maintained characteristic immunophenotypes in BM/PB. Potentially misleading variations included 1 case of MCL that failed to express CD5 in BM and likely would have been immunophenotypically misclassified as a marginal zone lymphoma and another MCL that expressed moderate CD23 in PB and would have required additional studies for precise classification. The remaining major and minor variations would not have affected interpretation.

Immunophenotype does not correlate with lymph node histology in chronic lymphocytic leukemia/small lymphocytic lymphoma.

The presence of prominent proliferation centers (PCs) in lymph nodes (LNs) involved with chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) has been associated with atypical blood smear morphology. Atypical CLL has in turn been associated with variant immunophenotypes and poor outcome. However, the significance of abundant PCs remains controversial. We have analyzed the flow cytometric immunophenotypic features of 54 CLL/SLL LNs and correlated these findings with the morphologic and clinical features. The LN histology was assigned to one of two groups based on the prominence of PCs: Group I LNs contained scattered small, sometimes ill-defined PCs in a background of monotonous small round lymphocytes. Group II LNs had increased numbers and sizes of PCs resulting in an obviously nodular appearance at low magnification. Flow cytometry was performed using broad three- or four-color antibody panels that included anti-CD5, CD19, CD20, CD23, CD38, FMC7, and surface immunoglobulin (sIg). The intensity of expression of all markers was scored semi-quantitatively using isotypic controls and internal positive and negative populations as standards. There were 32 group I and 22 group II LNs that, by definition, expressed CD19, CD5, and CD23. Little variability was seen in the intensity of expression of CD19, and the majority of cases expressed CD23 brightly. CD5 varied from very dim to an intensity similar to that of normal T cells; the majority had an intermediate level of CD5 expression. FMC7 was expressed to a significant extent in 11 cases (21%). CD20 was relatively bright in 17 cases (32%). sIg was dim in 29 cases (55%) and moderate or bright in 24 cases (45%). CD38 was expressed significantly in 25 cases (47%). There was no correlation between histologic group and intensity of expression of any individual marker or with an immunophenotypic atypia score based on FMC7, CD20, and sIg. There was also no correlation between morphology or immunophenotype and clinical features. These findings do not support the interpretation that the prominence of proliferation centers in CLL/SLL LNs defines biologically distinct subtypes.