In vivo correlation of near-infrared transillumination and visual inspection with bitewing radiography for the detection of interproximal caries in permanent and primary teeth.

PURPOSE: To evaluate near-infrared light transillumination (NILT) for interproximal caries detection in children by comparing the correlation between both NILT and visual inspection (ICDAS) with bitewing (BW) radiography and by investigating possible differences in caries detection with NILT between primary and permanent teeth. METHODS: From 35 patients, 121 and 63 interproximal surfaces in, respectively, primary and permanent teeth were included. NILT images were obtained using DIAGNOcam™ (KaVo) and scored by two calibrated raters. A consensus diagnosis was reached for BW radiography; whereas, the ICDAS scores were obtained by one calibrated rater. Weighted Kappa (wκ) was used to evaluate inter- and intra-rater reliability of NILT and to evaluate the correlation between NILT, ICDAS and BW radiography. RESULTS: The correlation between NILT and BW radiography was moderate to substantial for primary teeth [Rater 1: wκ = 0.61 (95% CI = 0.49-0.75), Rater 2: wκ = 0.55 (95% CI = 0.41-0.69)] and fair for permanent teeth [Rater 1: wκ = 0.34 (95% CI = 0.15-0.53), Rater 2: wκ = 0.33 (95% CI = 0.08-0.58)]. The correlation between ICDAS and BW radiography was moderate for primary teeth [wκ = 0.49 (95% CI = 0.35-0.63)] and substantial for permanent teeth [wκ = 0.62 (95% CI = 0.32-0.92)]. No significant differences were found between primary and permanent teeth. CONCLUSION: NILT cannot be recommended as a single diagnostic tool for interproximal caries detection in primary teeth. The number of false negatives for dentine caries, especially in first primary molars, was too high. For the use in permanent teeth, NILT could be more accurate than BW radiography.

The perlecan fragment LG3 regulates homing of mesenchymal stem cells and neointima formation during vascular rejection.

Transplant vasculopathy is associated with neointimal accumulation of recipient-derived mesenchymal stem cells. Increased circulating levels of LG3, a C-terminal fragment of perlecan, were found in renal transplant patients with vascular rejection. Here, we evaluated whether LG3 regulates the migration and homing of mesenchymal stem cells and the accumulation of recipient-derived neointimal cells. Mice were transplanted with a fully-MHC mismatched aortic graft followed by intravenous injection of recombinant LG3. LG3 injections increased neointimal accumulation of α-smooth muscle actin positive cells. When green fluorescent protein (GFP)-transgenic mice were used as recipients, LG3 injection favored accumulation of GFP+ cells to sites of neointima formation. LG3 increased horizontal migration and transmigration of mouse and human MSC in vitro and led to increased ERK1/2 phosphorylation. Neutralizing ß1 integrin antibodies or use of mesenchymal stem cells from α2 integrin-/- mice decreased migration in response to recombinant LG3. Reduced intima-media ratios and decreased numbers of neointimal cells showing ERK1/2 phosphorylation were found in α2-/- recipients injected with recombinant LG3. Collectively, our results suggest that LG3, through interactions with α2ß1 integrins on recipient-derived cells leading to activation of ERK1/2 and increased migration, favors myointimal thickening.

Collagen receptor integrins: rising to the challenge.

Integrins are alphabeta heterodimeric receptors that connect the extracellular environment with intracellular signaling events. Integrins are important for normal development and function, but are also involved in the pathogenesis of diseases including cancer, autoimmunity and heart disease. We will review the present data on a family of integrins, the collagen receptors that include the alpha1beta1, alpha2beta1, alpha1beta1 and alpha1beta1 integrins. We will describe the knowledge gained from genetic deletion of each integrin in animal models. Mice lacking any single collagen receptor display no overt defect. However, studies using the alpha1beta1 and alpha2beta1 integrin-deficient mice indicate that these receptors play an important role in innate immunity, inflammation and autoimmunity. Finally, we will elucidate the interesting and sometimes overlapping roles for alpha1beta1 and alpha2beta1 integrins in disease and will propose potential stategies to therapeutically target these receptors to alleviate or treat disease.

Unusual form of AV nodal Wenckebach block.

A 73-year-old man had a fast atrioventricular (AV) nodal pathway accidentally ablated 4 years before, while attempting to ablate a septally located concealed accessory pathway (AP). After initiation of treatment with beta-blockers, because of systemic arterial hypertension, the patient presented to the emergency room complaining of a markedly diminished exercise tolerance. The 12 lead ECG showed an interesting AV nodal Wenckebach sequence, interrupted by P waves retrogradely conducted through the AP. The mechanisms explaining the ECG are discussed.

Mammary epithelial cell-cycle progression via the alpha(2)beta(1) integrin: unique and synergistic roles of the alpha(2) cytoplasmic domain.

The alpha(2)beta(1) integrin supports cell-cycle progression of mammary epithelial cells adherent to type I collagen matrices. Integrin collagen receptors containing the alpha(2) cytoplasmic domain stimulated expression of cyclin E and cyclin-dependent kinase (cdk)2, resulting in cyclin E/cdk2 activation in the absence of growth factors other than insulin. Integrin collagen receptors in which the alpha(2) cytoplasmic domain was replaced by the alpha(1) cytoplasmic domain or an alpha(2) subunit cytoplasmic domain truncated after the GFFKR sequence failed to stimulate cyclin E/cdk2 activation or entry into S phase in the absence of growth factors. Although overexpression of cyclins D or E or cdk2 in cells expressing the integrin collagen receptor with the alpha(1)-integrin cytoplasmic domain did not restore G(1) progression when mammary epithelial cells adhered to type I collagen, co-expression of cyclin E and cdk2 did rescue the ability of the transfectants to enter S phase. Activation of cyclin E/cdk2 complex by mammary epithelial cells required synergy between adhesion mediated by an integrin collagen receptor containing the alpha(2)-integrin subunit cytoplasmic domain and the insulin receptor.

Specific residues within the alpha 2 integrin subunit cytoplasmic domain regulate migration and cell cycle progression via distinct MAPK pathways.

The alpha(2) integrin subunit cytoplasmic domain is necessary for epidermal growth factor (EGF)-stimulated chemotactic migration and insulin-dependent entry into S-phase of mammary epithelial cells adherent to type I collagen. Truncation mutants revealed that the seven amino acids, KYEKMTK, in addition to the GFFKR motif were sufficient for these functions. Mutation of tyrosine 1134 to alanine inhibited the ability of the cells to phosphorylate p38 MAPK and to migrate in response to EGF but had only a modest effect on the ability of the cells to induce sustained phosphorylation of the ERK MAPK, to up-regulate cyclin E and cdk2 expression, and to enter S-phase when adherent to type I collagen. Conversely, mutation of the lysine 1136 inhibited the ability of the cells to increase cyclin E and cdk2 expression, to maintain long term phosphorylation of the ERK MAPK, and to enter S-phase but had no effect on the ability of the cells to phosphorylate the p38 MAPK or to migrate on type I collagen in response to EGF. Methionine 1137 was essential for both migration and entry into S-phase. Thus, distinctly different structural elements of the alpha(2) integrin cytoplasmic domain are required to engage the signaling pathways leading to cell migration or cell cycle progression.

Aberrant expression of T-cell-associated antigens on B-cell non-Hodgkin lymphomas.

We describe 9 well-characterized cases of B-cell non-Hodgkin lymphoma (NHL) that showed aberrant expression of T-cell-associated antigens by 2-color flow cytometry. Cases were as follows: chronic lymphocytic leukemia/small lymphocytic lymphoma, 4; follicle center cell lymphoma, 2; mantle cell lymphoma, 1; and diffuse large B-cell lymphoma, 2. CD2 was the most commonly expressed antigen (5 cases). CD8 and CD7 were identified in 2 cases each, including 1 case that expressed both CD7 and CD4. The disease course and response to treatment were compatible with the type and stage of lymphoma. No unusually aggressive behavior was noted in any case. A control group of 59 cases of benign lymph nodes analyzed during the same period showed no aberrant expression of T-cell-associated antigens; thus, such expression is not a feature of benign lymphoid proliferations. Study of these B-cell lymphomas may prove invaluable to study aberrant activation of silent or repressed T-cell differentiation genes. CD2-expressing B-cell NHLs may represent clonal expansion of CD2+ B lymphocytes that normally constitute a small fraction of peripheral B lymphocytes and should not be confused with composite B- and T-cell lymphomas. Unless aggressive behavior is noted consistently, no aggressive treatment is justified.

alpha 2 integrin subunit cytoplasmic domain-dependent cellular migration requires p38 MAPK.

The alpha(2) integrin subunit cytoplasmic domain uniquely supported epidermal growth factor (EGF)-stimulated migration on type I collagen. p38 MAP kinase- and phosphatidylinositol 3-kinase-specific inhibitors, but not a MEK-specific inhibitor, eliminated EGF-stimulated and unstimulated alpha(2)-cytoplasmic domain-dependent migration. Following adhesion to collagenous matrices, cells expressing the full-length alpha(2) integrin subunit, but not cells expressing a chimeric alpha(2) integrin subunit in which the alpha(2)-cytoplasmic domain was replaced by the cytoplasmic domain of the alpha(1)-subunit, exhibited sustained and robust phosphorylation of p38 MAP kinase. Expression of dominant negative p38 MAP kinase inhibited alpha(2)-cytoplasmic domain-dependent, EGF-stimulated migration as well as unstimulated migration on collagen. Expression of constitutively active Rac1(Val-12) augmented p38 MAP kinase activation and alpha(2)-cytoplasmic domain-dependent migration. It also rescued the ability of cells expressing the alpha(1)-cytoplasmic domain to activate p38 MAPK and to migrate. These results suggest that the alpha(2) integrin cytoplasmic domain uniquely stimulates the p38 MAP kinase pathway that is required for unstimulated and EGF-stimulated migration on type I collagen.

Composite prolymphocytoid and hodgkin transformation of chronic lymphocytic leukemia.

The indolent course of chronic lymphocytic leukemia/small lymphocytic lymphoma (CLL/SLL) is occasionally altered by transformation to a histologically distinct, rapidly progressive, and clinically unresponsive hematologic malignant neoplasm. We report a case of CLL that, after 3 years of slowly progressive disease and treatment with single-agent chemotherapy (fludarabine phosphate), underwent a composite prolymphocytoid and classic Hodgkin lymphoma transformation. The diagnosis of classic Hodgkin lymphoma was based on the presence of Reed-Sternberg cells with typical morphologic structure and immunophenotype (CD15(+), CD30(+), CD45(-), CD20(-)) associated with the characteristic polymorphous inflammatory background consisting of numerous eosinophils, plasma cells, and reactive T lymphocytes. The remainder of the lymph node and the peripheral blood showed increased numbers of prolymphocytes admixed with typical small CLL cells. Recognition of such a transformation is of the utmost importance, since histologically similar Reed-Sternberg-like cells may be seen in Richter transformation. In contrast to prolymphocytoid transformation of CLL, Richter syndrome is rapidly fatal, with a median survival of 4 to 5 months. The patient pursued a clinical course similar to pure prolymphocytoid transformation and died with disease after 30 months following treatment with combination chemotherapy.

Role of the alpha1 and alpha2 integrin cytoplasmic domains in cell morphology, motility and responsiveness to stimulation by the protein kinase C pathway.

The alpha1beta1 and alpha2beta1 integrins, extracellular matrix receptors for collagens and/or laminins, have similarities in structure and ligand binding. Recent studies suggest that the two receptors mediate distinct post-ligand binding events and are not simply redundant receptors. To discern the mechanisms by which the two receptors differ, we focused on the roles of the cytoplasmic domains of the alpha subunits. We expressed either full-length alpha1 integrin subunit cDNA (X1C1), full-length alpha2 integrin subunit cDNA (X2C2), chimeric cDNA composed of the extracellular and transmembrane domains of alpha2 subunit and the cytoplasmic domain of alpha1 (X2C1), chimeric cDNA composed of the extracellular and transmembrane domains of alpha1 subunit and the cytoplasmic domain of alpha2 (X1C2), alpha1 cDNA truncated after the GFFKR sequence (X1C0) or alpha2 cDNA truncated after the GFFKR sequence (X2C0) in K562 cells. Although the cytoplasmic domains of the alpha1 and alpha2 subunits were not required for adhesion, the extent of adhesion at low substrate density was enhanced by the presence of either the alpha1 or alpha2 cytoplasmic tail. Spreading was also influenced by the presence of an alpha subunit cytoplasmic tail. Activation of the protein kinase C pathway with phorbol dibutyrate-stimulated motility that was dependent upon the presence of the alpha2 cytoplasmic tail. Both the phosphatidylinosotide-3-OH kinase and the mitogen-activated protein kinase pathways were required for phorbol-activated, alpha2-cytoplasmic tail-dependent migration.

Lack of expression of surface immunoglobulin light chains in B-cell non-Hodgkin lymphomas.

We describe 10 cases of B-cell non-Hodgkin lymphoma (NHL) that did not express immunoglobulin kappa or lambda light chains by dual-color flow cytometry. Cases were identified from 298 consecutive cases of B-cell NHL and included follicular center cell lymphoma, diffuse large B-cell lymphoma, small noncleaved cell lymphoma, and small lymphocytic lymphoma. One case did not express any immunoglobulin heavy chain (IgH) as well; however, isolated expression of IgG heavy chain was seen in another case. Immunoglobulin heavy chains were not part of the lymphoma panel in other cases. All 3 cases in which gene rearrangement studies were performed showed rearrangement of IgH genes, including the case that did not express surface IgH chains. Immunoglobulin kappa light chain genes were rearranged in 2 of 3 cases and were in germline configuration in the third. All 147 cases of benign lymph nodes analyzed by flow cytometry showed polyclonal expression of immunoglobulin kappa and lambda light chains. Because of the absence of surface immunoglobulin light chains, these tumors must be distinguished from precursor B-cell acute lymphoblastic leukemia, plasma cell tumors, and rare cases of florid follicular hyperplasia that do not express surface immunoglobulins. The absence of immunoglobulin expression on malignant B cells can result from defects at any level from gene transcription to translocation of fully assembled proteins to the cell surface.

Acute lymphoblastic leukemia with an unusual t(8;14)(q11.2;q32): a Pediatric Oncology Group Study.

We present the clinicopathologic findings and survival data on 10 patients with acute lymphoblastic leukemia (ALL) and a rare t(8;14)(q11.2;q32). There were five male and five female patients, nine Caucasians and one Black, aged 4-17 (median 10.9) years. Three had Down syndrome. Eight (80%) patients had a white blood cell (WBC) count <50 x 109/l at presentation. No patient had central nervous system involvement or a mediastinal mass. Two patients had concurrent splenomegaly and hepatomegaly. Adenopathy was absent in four, minimal in three, moderate in one and prominent in two patients. All eight cases where immunophenotyping was performed by flow cytometry showed a B-precursor phenotype with expression of CD10 (CALLA). Only one case exhibited t(8;14)(q11.2;q32) as the sole karyotypic abnormality. Three patients were classified as standard-risk and seven high-risk by NCI (National Cancer Institute) consensus risk group categories. All patients achieved complete remission and seven patients were in complete continuous remission (CCR) after chemotherapy designed for B-precursor ALL. Three patients relapsed after 23.5, 31.3 and 32.1 months of EFS; the first patient also had t(9;22)(q34;q11), the second had a WBC count of 126 x 109/l at presentation while the third patient had no high risk features except for age 10 years. Thus, from our data, the t(8;14)(q11.2;q32) does not appear to confer an increased risk of relapse. Further observations are needed to confirm this conclusion.

Primary gastric plasmacytoma: a rare cause of hypertrophic gastritis in an adolescent.

BACKGROUND: This report describes a 16-year-old patient with gastric rugal hypertrophy caused by a primary gastric plasmacytoma. She had a 3-month history of nausea and burning abdominal pain. Radiographic studies showed giant rugal hypertrophy. Superficial endoscopic gastric biopsies showed mild inflammation with plasma cells of polyclonal origin in the mucosa. When symptoms persisted, she underwent laparoscopic full-thickness gastric biopsy. There was monoclonal plasma cell infiltration histologically diagnostic of plasmacytoma and inconsistent with Helicobacter pylori-associated mucosa-associated lymphoid tissue (MALT) lymphoma. There was no evidence for involvement of the bone marrow or regional lymph nodes. The tumor did not respond to radiotherapy, necessitating total gastrectomy. METHODS: Blood samples were analyzed for interleukin (IL)-6 by enzyme-linked immunosorbent assay. Gastric biopsy and gastrectomy specimens were subjected to immunophenotyping for kappa and lambda light chains, CD45, CD20, and LN1 and to polymerase chain reaction analysis for herpes virus HHV8. RESULTS: There was no elevation in circulating IL-6 levels, militating against a pathogenesis akin to that of Castleman's disease. There was no evidence for infection with the Kaposi's sarcoma-associated herpes virus HHV8, which has recently been found in patients with multiple myeloma. CONCLUSIONS: This diagnosis and the characteristics of the tumor are very unusual, if not unique, for a patient of this age. The diagnostic evaluation of this patient also demonstrates the importance of deep endoscopic or full-thickness biopsies in some children with hypertrophic gastritis.

Collagen receptor control of epithelial morphogenesis and cell cycle progression.

To define the unique contributions of the alpha subunit cytoplasmic tails of the alpha(1)beta(1) and alpha(2)beta(1) integrin to epithelial differentiation and branching morphogenesis, a variant NMuMG cell line lacking alpha(1)beta(1) and alpha(2)beta(1) integrin expression was stably transfected with the full-length alpha(2) integrin subunit cDNA (X2C2), chimeric cDNA consisting of the extracellular and transmembrane domains of the alpha(2) subunit and the cytoplasmic domain of the alpha(1) subunit (X2C1), or alpha(2) cDNA truncated after the GFFKR sequence (X2C0). The X2C2 and X2C1 transfectants effectively adhered, spread, and formed focal adhesion complexes on type I collagen matrices. The X2C0 transfectants were less adherent to low concentrations of type I collagen, spread less well, and formed poorly defined focal adhesion complexes in comparison to the X2C2 and X2C1 transfectants. The X2C2 and X2C1 transfectants but not the X2C0 transfectants proliferated on collagen substrates. Only the X2C2 transfectants developed elongate branches and tubules in three-dimensional collagen gels and migrated on type I collagen. These findings suggest a unique role for the alpha(2) integrin cytoplasmic domain in postligand binding events and cooperative interactions with growth factors that mediate epithelial differentiation and branching morphogenesis. Either intact alpha(1) or alpha(2) integrin subunit cytoplasmic domain can promote cell cycle progression.

Acute promyelocytic leukemia with additional chromosomal abnormalities and absence of Auer rods.

We report 4 acute promyelocytic leukemia cases that demonstrated karyotypic abnormalities in addition to the classic t(15;17) translocation and did not contain any Auer rods in leukemic blasts and dysplastic promyelocytes, either in the peripheral blood or in the bone marrow. Morphologically, 2 cases were characterized as the common or hypergranular type, and 2 were otherwise typical of the microgranular variant. Three patients had typical clinical and laboratory signs of disseminated intravascular coagulation. Immunophenotypic analysis of the blasts and dysplastic promyelocytes by dual-color flow cytometry revealed an immunoprofile consistent with acute promyelocytic leukemia. Cytogenetic analysis of the bone marrow revealed the following karyotypes: case 1, [47,XY,t(15;17)(q22;q12),+21]; case 2, [47,XY,t(15;17)(q22;q12),-16,+2 mar]; case 3, [47,XX,t(15;17)(q22;q12)ider(17)(q10),+8]; and case 4, [47,XY,der(5)t(5;?9)(p15;q12).t(15;17)(q22;q12]. Review of an additional 7 cases with t(15;17) as the sole cytogenetic abnormality revealed Auer rods in all cases. Our findings emphasize the importance of cytogenetics in evaluating acute myeloid leukemias. Acute promyelocytic leukemia without Auer rods, which may be morphologically confused with other types of leukemia (in particular, acute myeloblastic leukemia, type M2 or M5) or agranulocytosis with maturation arrest, appears to be associated with additional chromosomal abnormalities and possibly a poorer prognosis.

The Megakaryocyte/Platelet-specific enhancer of the alpha2beta1 integrin gene: two tandem AP1 sites and the mitogen-activated protein kinase signaling cascade.

The alpha2beta1 integrin, a collagen receptor on platelets and megakaryocytes, is required for normal platelet function. Transcriptional regulation of the alpha2 integrin gene in cells undergoing megakaryocytic differentiation requires a core promoter between bp -30 and -92, a silencer between bp -92 and -351, and megakaryocytic enhancers in the distal 5' flank. We have now identified a 229-bp region of the distal 5' flank of the alpha2 integrin gene required for high-level enhancer activity in cells with megakaryocytic features. Two tandem AP1 binding sites with dyad symmetry are required for enhancer activity and for DNA-protein complex formation with members of the c-fos/c-jun family. The requirement for AP1 activation suggested a role for the mitogen-activated protein kinase (MAPK) signaling pathway in regulating alpha2 integrin gene expression. Inhibition of the MAP kinase cascade with PD98059, a specific inhibitor of MAPK kinase 1, prevented the expression of the alpha2 integrin subunit in cells induced to become megakaryocytic. We provide a model of megakaryocytic differentiation in which expression of the alpha2 integrin gene requires signaling via the MAP kinase pathway to activate two tandem AP1 binding sites in the alpha2 integrin enhancer.

Downstream events in mammary gland morphogenesis mediated by reexpression of the alpha2beta1 integrin: the role of the alpha6 and beta4 integrin subunits.

Our previous studies demonstrated that reexpression of the alpha2beta1 integrin by a poorly differentiated breast carcinoma cell line, Mm5MT, resulted in dramatic reversion of a malignant phenotype to a differentiated epithelial phenotype. We hypothesized that reexpression of the alpha2beta1 integrin may regulate expression of other genes, the expression of which contributed to the dramatic phenotypic change. We now show that reexpression of the alpha2beta1 integrin results in up-regulation of both the alpha6 and beta4 integrin subunits but no change in the alpha1, alpha3, alpha5, or beta1 integrin subunits or E-cadherin. To further investigate the role of the alpha6 and beta4 integrin subunits in mediating the phenotypic changes elicited by reexpression of the alpha2beta1 integrin, the alpha6 or beta4 integrin subunit was expressed in our Mm5MT model. Expression of either subunit increased adhesion to laminin-1. Although adhesion to collagen was unaltered, contraction of three-dimensional collagen gels was reduced. Expression of either the alpha6 or beta4 integrin subunit also restored some aspects of a less malignant phenotype, including the acquisition of contact inhibition and diminution of anchorage-dependent and anchorage-independent growth rates. The alpha6 and beta4 transfectants formed three-dimensional organized structures when grown in gels of reconstituted basement membrane but did not form the highly branched, duct-like structures formed by the alpha2 transfectants. In contrast to the reduced invasiveness of the alpha2 transfectants, the alpha6 and beta4 transfectants retained an invasive phenotype. These results suggest that expression of the alpha6beta4 integrin contributes to some but not all of the phenotypic changes elicited by reexpression of the alpha2 integrin subunit and modulates the function of other integrins on these cells. Using our Mm5MT model, we are defining the cascade of integrin expression required for maintenance of the differentiated mammary epithelial cell phenotype.

Guidelines for the diagnosis of leukemia or lymphoma in children.

Our progress in understanding and treating pediatric acute leukemia and lymphoma is one of the success stories of cancer biology and management. Event-free survival for children with acute leukemia or lymphoma has improved progressively during the past four decades. The advances in the cell and molecular biology of acute leukemia and lymphoma that have been made can help determine both prognosis and therapy; however, the pathologic evaluation of bone marrow and lymph node specimens must be directed appropriately to benefit from these advances. We present guidelines for the pathologic evaluation of bone marrow and lymph node specimens to maximize the chance that each patient will benefit from our increased understanding of these diseases.

Bone marrow staging in patients with non-Hodgkin's lymphoma: is flow cytometry a useful test?

BACKGROUND: Flow cytometric analysis of bone marrow often is used as an adjunct to morphologic evaluation in the staging of patients with non-Hodgkin's lymphoma (NHL). The goal of this study was to define objectively the benefit of flow cytometry in this setting. METHODS: The authors reviewed retrospectively all bone marrow specimens submitted between January 1992 and December 1994 to the Washington University Department of Pathology for flow cytometric immunophenotyping to rule out NHL. Results of morphologic examination and flow cytometry were reviewed independently and the ability to detect bone marrow involvement compared. RESULTS: Two hundred and seventy-three bone marrow specimens from 190 patients with an established diagnosis of NHL were submitted for flow cytometric analysis at initial presentation, restaging, and/or recurrence. Morphologic evaluation was negative in 69%, positive in 23%, and equivocal in 8%. Flow cytometry was negative in all but 1 morphologically negative bone marrow specimens and 40% of morphologically involved bone marrow specimens. Two of 23 morphologically equivocal bone marrow specimens were positive by flow cytometry. An additional 86 specimens were obtained to rule out NHL in patients without an established diagnosis of NHL. The majority of patients had a history of human immunodeficiency virus infection, cytopenia, or unexplained fevers. Morphologically, one specimen was involved with NHL, 5 were equivocal, and 80 were negative. All specimens were negative by flow cytometry. CONCLUSIONS: In this study, flow cytometric analysis improved the detection of NHL in bone marrow in only 3 of 273 samples, 2 of which were suspicious morphologically. Flow cytometry of bone marrow aspirates has a limited role in the routine staging and follow-up of patients with an established diagnosis of NHL.