Evaluating iQ-CheckTM real-time PCR to detect Salmonella from poultry environmental samples in Fraser Valley, British Columbia, Canada.

Salmonella is a ubiquitous pathogen that accounts for foodborne and livestock illnesses worldwide. Robust surveillance programs must be implemented to maintain human and animal health and limit economic losses. The poultry industry in particular demands the implementation of rapid Salmonella detection methods that will facilitate the timely availability of results in a manner allowing actions to be taken for the associated poultry products. One such method, the iQ-CheckTM real-time PCR, has significantly reduced turnaround times compared to conventional culture methods. In this study, a total 733 poultry environmental samples was received from farms in the Fraser Valley of British Columbia, Canada and the real-time PCR method was assessed for its ability to detect Salmonella in comparison to the currently used culture protocol. The iQ-Check real-time PCR method was effective at accurately screening out the majority of negative samples, and demonstrated a very strong correlation with the culture method. This was especially true when selective enrichment was performed before PCR, with sensitivity, specificity, and accuracy values reaching 100.0%, 98.5%, and 98.9%, respectively. These results demonstrate that rapid detection methods could be effectively introduced into current Salmonella surveillance workflows dealing with environmental poultry samples to reduce turnaround times and minimize economic impacts on producers.

Retrospective and Prospective Evaluations of Mammography Screening Narratives.

We investigated the role of previous experience when providing summary judgments of mammography narratives. A total of 807 women who either did or did not have previous experience of a mammogram were presented with a written description of a mammography visit. We manipulated the presentation position of a negative element within the narrative to alter its accessibility in memory and determine whether the latter impacted equally on two types of summary judgments. After the narrative presentation, participants were asked to provide both retrospective and prospective evaluations, that is, summary judgments about the described event and an appraisal of the likelihood of participating in future instances of such event, respectively. A recency effect was observed only for retrospective but not for prospective evaluations. When examined only for the subset of women who had undergone a mammography visit themselves, prospective evaluations were shown to be predicted by the reported quality of the mammography participants experienced themselves. The findings support and extend the accessibility model of emotional self-report and suggest that own experience leaks into evaluations of hypothetical scenarios by selectively impacting on prospective evaluations.

Exploring the roles of physical effort and visual salience within the proximity effect.

BACKGROUND: Recent work has explored the effectiveness of the Proximity Effect, where increasing the physical distance between consumer and snacks reduces intake. Foods requiring less effort to attain, or being more visually appealing, are seen to be consumed more. Relatedly, perceived effort and visual salience are suggested mechanisms for the proximity effect, but no prior studies have directly manipulated these in association with the effect. Two between-subjects studies conducted in university laboratories are presented. METHOD: Twenty chocolate brownies that were either wrapped or unwrapped (Study 1, N = 85), or 250g of M&M's, either colourful or plain brown (Study 2, N = 80), were presented as effort and salience manipulations respectively to participants at either 20 cm or 70 cm. Consumption was measured as 'likelihood of consumption' (Yes/No) and 'actual consumption' (units/grams). Potential moderating variables including perceived effort and perceived visual salience were also measured. RESULTS: Likelihood of consumption was positively predicted by perceived visual salience in both Studies, and by distance in Study 2. Significant main effects of distance, p < .001, ȵ2 = 0.102 (20 cm > 70 cm), effort, p < .001, ȵ2 = 0.089 (unwrapped > wrapped), and distance × effort interaction, p = .003, ȵ2 = 0.111, were observed in Study 1 for actual consumption. A main effect of distance was found in Study 2 for actual consumption, p < .001, ȵ2 = 0.062 (20 cm > 70 cm). Perceived visual salience positively correlated with actual consumption in both Studies. CONCLUSIONS: Increasing physical effort and placing snacks further away appear to act independently and interactively to reduce snack consumption. Manipulating snack colour does not appear to influence consumption, whereas perceptions of visual salience appear to influence consumption. As such, perceived visual salience and physical effort are thought to be key mechanisms underpinning the proximity effect. PRE-REGISTRATION: Both Studies were pre-registered on the Open Science Framework (Study 1: 10.31234/osf.io/rmnys; Study 2: 10.31234/osf.io/u8bsz).

Interdomain communication in the phosphatidylcholine regulatory enzyme, CCTα, relies on a modular αE helix.

CTP:phosphocholine cytidylyltransferase (CCT), the rate-limiting enzyme in phosphatidylcholine (PC) synthesis, is an amphitropic enzyme that regulates PC homeostasis. Recent work has suggested that CCTα activation by binding to a PC-deficient membrane involves conformational transitions in a helix pair (αE) that, along with a short linker of unknown structure (J segment), bridges the catalytic domains of the CCTα dimer to the membrane-binding (M) domains. In the soluble, inactive form, the αE helices are constrained into unbroken helices by contacts with two auto-inhibitory (AI) helices from domain M. In the active, membrane-bound form, the AI helices are displaced and engage the membrane. Molecular dynamics simulations have suggested that AI displacement is associated with hinge-like bending in the middle of the αE, positioning its C terminus closer to the active site. Here, we show that CCTα activation by membrane binding is sensitive to mutations in the αE and J segments, especially within or proximal to the αE hinge. Substituting Tyr-213 within this hinge with smaller uncharged amino acids that could destabilize interactions between the αE helices increased both constitutive and lipid-dependent activities, supporting a link between αE helix bending and stimulation of CCT activity. The solvent accessibilities of Tyr-213 and Tyr-216 suggested that these tyrosines move to new partially buried environments upon membrane binding of CCT, consistent with a folded αE/J structure. These data suggest that signal transduction through the modular αE helix pair relies on shifts in its conformational ensemble that are controlled by the AI helices and their displacement upon membrane binding.

Remodeling of the interdomain allosteric linker upon membrane binding of CCTα pulls its active site close to the membrane surface.

The rate-limiting step in the biosynthesis of the major membrane phospholipid, phosphatidylcholine, is catalyzed by CTP:phosphocholine cytidylyltransferase (CCT), which is regulated by reversible membrane binding of a long amphipathic helix (domain M). The M domain communicates with the catalytic domain via a conserved ∼20-residue linker, essential for lipid activation of CCT. Previous analysis of this region (denoted as the αEC/J) using MD simulations, cross-linking, mutagenesis, and solvent accessibility suggested that membrane binding of domain M promotes remodeling of the αEC/J into a more compact structure that is required for enzyme activation. Here, using tryptophan fluorescence quenching, we show that the allosteric linker lies superficially on the membrane surface. Analyses with truncated CCTs show that the αEC/J can interact with lipids independently of the M domain. We observed strong FRET between engineered tryptophans in the αEC/J and vesicles containing dansyl-phosphatidylethanolamine that depended on the native J sequence. These data are incompatible with the extended conformation of the αE helix observed in the previously determined crystal structure of inactive CCT but support a bent αE helix conformation stabilized by J segment interactions. Our results suggest that the membrane-adsorbed, folded allosteric linker may partially cover the active site cleft and pull it close to the membrane surface, where cytidyl transfer can occur efficiently in a relatively anhydrous environment.

Exploring the underpinning mechanisms of the proximity effect within a competitive food environment.

OBJECTIVE: One method of influencing an individual's food consumption involves placing unhealthy snacks further away from individuals, known as the "proximity effect". However, only one laboratory study has explored the effect while both an unhealthy and a healthy option are presented simultaneously. Further, little is known about the potential underpinning mechanisms of the effect. The current study aims to replicate the proximity effect in a competitive environment, and to explore the role of visual salience and effort in the proximity effect. METHOD: Fifty-six participants were asked to complete a two-part questionnaire under the cover story of a relaxation study. Two bowls were presented to participants, each containing either 250 g chocolate M&M's or 250 g mixed fruit pieces. Each bowl was positioned either 20 cm or 70 cm from the participant, creating four proximity conditions. Consumption of each snack was compared between proximity conditions. RESULTS: No main effects were found. A significant interaction between snack type and chocolate position was found (p = .010, ȵ2 = 0.159), with fruit consumption being significantly higher when chocolate was at located at 20 cm compared to 70 cm (53.35 g vs 22.35 g, p = .042). Higher visual salience of each snack type correlated to more of the snack being consumed, ps < .017. Results were similar when calories consumed were analysed. CONCLUSIONS: We found an unconventional proximity effect where the consumption of a snack did not depend on its position, but rather the relative position of another snack. Implications of the study could inform café and supermarket layouts to exploit the interaction between moving healthy items closer in addition to moving unhealthy items further away, in order to maximise choice of healthy items.

Clinical Ultrasound Is Safe and Highly Specific for Acute Appendicitis in Moderate to High Pre-test Probability Patients.

INTRODUCTION: Clinical ultrasound (CUS) is highly specific for the diagnosis of acute appendicitis but is operator-dependent. The goal of this study was to determine if a heterogeneous group of emergency physicians (EP) could diagnose acute appendicitis on CUS in patients with a moderate to high pre-test probability. METHODS: This was a prospective, observational study of a convenience sample of adult and pediatric patients with suspected appendicitis. Sonographers received a structured, 20-minute CUS training on appendicitis prior to patient enrollment. The presence of a dilated (>6 mm diameter), non-compressible, blind-ending tubular structure was considered a positive study. Non-visualization or indeterminate studies were considered negative. We collected pre-test probability of acute appendicitis based on a 10-point visual analog scale (moderate to high was defined as >3), and confidence in CUS interpretation. The primary objective was measured by comparing CUS findings to surgical pathology and one week follow-up. RESULTS: We enrolled 105 patients; 76 had moderate to high pre-test probability. Of these, 24 were children. The rate of appendicitis was 36.8% in those with moderate to high pre-test probability. CUS were recorded by 33 different EPs. The sensitivity, specificity, and positive and negative likelihood ratios of EP-performed CUS in patients with moderate to high pre-test probability were 42.8% (95% confidence interval [CI] [25-62.5%]), 97.9% (95% CI [87.5-99.8%]), 20.7 (95% CI [2.8-149.9]) and 0.58 (95% CI [0.42-0.8]), respectively. The 16 false negative scans were all interpreted as indeterminate. There was one false positive CUS diagnosis; however, the sonographer reported low confidence of 2/10. CONCLUSION: A heterogeneous group of EP sonographers can safely identify acute appendicitis with high specificity in patients with moderate to high pre-test probability. This data adds support for surgical consultation without further imaging beyond CUS in the appropriate clinical setting.

Neutrophilic leukocytosis in advanced stage polycythemia vera: hematopathologic features and prognostic implications.

Polycythemia vera in 20-30% of cases progresses towards post-polycythemic myelofibrosis, an advanced phase characterized by decreased red blood cells counts and increasing splenomegaly with extramedullary hematopoiesis. There is evidence that the presence of neutrophilic leukocytosis at polycythemia vera disease outset is associated with an increased risk of recurrent thrombosis. However, its clinical significance when developing later in the course of the disease is not well defined. Over a period of 8 years we identified from the files of two reference centers 10 patients (7M/3F, median age: 68 years) who developed persistent absolute leukocytosis ≥ 13 × 109/l (median: 25.1 × 109/l; range: 16.1-89.7 × 109/l) at or around the time of diagnosis of post-polycythemic myelofibrosis (median interval from diagnosis:0 months; range: -6/31) and persisted for a median period of 13 months. Peripheral blood smears showed numerous neutrophils without dysplastic features and, in four, ≥ 10% immature myeloid precursors. In five cases, corresponding marrow specimens obtained at or immediately after the onset of leukocytosis showed a markedly increased myeloid:erythroid ratio due to granulocytic proliferation. No change in JAK2 and BCR-ABL1 status or cytogenetic evolution was associated with the development of leukocytosis. The mutational status of CSF3R, SETBP1, and SRSF2, genes associated with other chronic myeloid neoplasms where neutrophilic leukocytosis occurs, was investigated but all cases showed wild-type only alleles. Four patients died after developing leukocytosis and one experienced worsening disease. Compared with a control group of post-polycythemic myelofibrosis patients (n=23) who never developed persistent leukocytosis, patients with leukocytosis showed higher white blood cells counts and a shorter overall survival. This is the first study describing the development of significant neutrophilic leukocytosis during advanced stages of polycythemia vera; it includes comprehensive hematologic, marrow morphological, molecular, and clinical data. Our findings suggest that persistent leukocytosis occurring at or around the time of progression to post-polycythemic myelofibrosis is associated with an overall more aggressive course of the disease.

Cyclin D1-positive diffuse large B-cell lymphoma with IGH-CCND1 translocation and BCL6 rearrangement: a report of two cases.

OBJECTIVES: To demonstrate and confirm the existence of cyclin D1-positive diffuse large B-cell lymphoma (DLBCL) with IGH-CCND1 rearrangement and discuss the rationale of differentiating this entity from blastoid and pleomorphic variants of mantle cell lymphoma (MCL). METHODS: Two cyclin D1-positive lymphomas with morphologic features of DLBCL and IGH-CCND1 translocations were characterized with respect to clinical features, as well as morphologic, immunophenotypic, cytogenetic, and molecular findings. RESULTS: The large tumor cells were CD20+, CD5-, CD10-, BCL6+, MUM1+, and cyclin D1+ in both cases. SOX11 was negative. Epstein-Barr virus-encoded RNA in situ hybridization demonstrated diffuse positivity in case 1. BCL6 and IGH-CCND1 rearrangements were identified by fluorescence in situ hybridization in both cases. Specifically, the diagnosis of a relapsed DLBCL with acquisition of IGH-CCND1 was rendered for case 1, molecularly confirmed by the detection of identical monoclonal IGH rearrangements between the initial diagnostic DLBCL and relapse lymphoma. CONCLUSIONS: Our study demonstrates convincingly that IGH-CCND1 rearrangement leading to cyclin D1 overexpression can occur in DLBCL and pose a potential diagnostic pitfall, requiring thorough knowledge of the clinicopathologic findings to allow accurate discrimination from a blastoid or pleomorphic MCL. The coexistence of IGH-CCND1 and IGH-BCL6 rearrangements suggest that BCL6 and cyclin D1 may cooperate in the pathogenesis of DLBCL.

Morphologic and cytogenetic differences between post-polycythemic myelofibrosis and primary myelofibrosis in fibrotic stage.

Polycythemia vera and primary myelofibrosis share a propensity to progress toward a myelofibrotic late stage with overlapping clinical characteristics. Bone marrow features potentially useful for distinguishing the two entities have not been thoroughly investigated and, currently, clinical history is used for purposes of disease classification. This study describes in detail the morphologic features of 23 cases of post-polycythemic myelofibrosis and 15 cases of primary myelofibrosis with a similar degree of fibrosis, from two large medical centers. Cytogenetic results were available in 19 post-polycythemic myelofibrosis and in 13 primary myelofibrosis cases. JAK2 status and follow-up information was available in all cases. Cellularity was increased in both groups, but more so in post-polycythemic myelofibrosis than in primary myelofibrosis. In post-polycythemic myelofibrosis, most megakaryocytes retained polycythemia vera-like features including normally folded and/or hyperlobulated nuclei devoid of severe maturation defects; only in a few cases were rare tight clusters present. In primary myelofibrosis cases, megakaryocytes showed pronounced anomalies, including increased nuclear:cytoplasmic ratio, abnormal clumping of chromatin and frequent tight clustering. No differences in blast number (<1%) or in the myeloid:erythroid ratio were observed. Post-polycythemic myelofibrosis showed a higher degree of karyotypic alterations and higher percentage of cases with complex karyotype and/or two or more clones. Chromosome 1 defects were common in post-polycythemic myelofibrosis, whereas isolated del(20q) was the most common alteration in primary myelofibrosis. No survival differences were noted between the two groups. Post-polycythemic myelofibrosis cases retain a distinct megakaryocytic morphology that represents a useful clue for differential diagnosis. In addition, they more often display a complex karyotype than do primary myelofibrosis cases. These results suggest that myelofibrosis in polycythemia vera represents a form of progression characterized by profound genetic damage whereas in primary myelofibrosis it is an intrinsic part of the phenotypic manifestation of the disease, not necessarily associated with adverse cytogenetics.

Bone marrow morphology predicts additional chromosomal abnormalities in patients with myelodysplastic syndrome with del(5q).

The current World Health Organization classification considers myelodysplastic syndrome with isolated del(5q) a distinct entity owing to its characteristic clinical and pathologic features. Recently, several studies have examined survival, leukemic transformation, and various prognostic factors in these patients. However, there is a lack of detailed comparative pathologic analysis of myelodysplastic syndrome cases in which del(5q) is present in association with additional cytogenetic abnormalities. We studied 26 cases of myelodysplastic syndrome at initial diagnosis with 5q- alone, 5q- plus 1 additional abnormality, and 5q- as part of a complex karyotype. Four of 17 patients had evidence of JAK2 V617F mutation. In contrast to cases of myelodysplastic syndrome with isolated 5q-, patients with additional abnormalities had normal mean corpuscular volume and decreased platelet counts (P < .001). Based on bone marrow examination, they were significantly more likely to have increased cellularity, trilineage dysplasia, lower proportion of small hypolobated megakaryocytes, higher number of blasts, and fibrosis. The presence of these morphologic features can be used to distinguish these more aggressive cases from those with myelodysplastic syndrome with isolated 5q- and a more benign clinical course.

Development of monocytosis in patients with primary myelofibrosis indicates an accelerated phase of the disease.

Primary myelofibrosis is a type of chronic myeloproliferative neoplasm characterized by progressive bone marrow failure with worsening cytopenia and in a subset of patients, progression to acute leukemia. Published data in patients with myelodysplastic syndromes have shown that the development of monocytosis in the course of myelodysplastic syndromes is associated with a poor prognosis. A similar occurrence has been only sporadically reported in patients with primary myelofibrosis. Over a period of four years we identified 10 out of 237 cases of primary myelofibrosis who developed persistent absolute monocytosis (>1 × 10(9)/l) during the course of disease (5 men and 5 women; median age/range: 68 years/52-82). Monocytosis developed at a median interval of 42 months from diagnosis (range: 1-180) and persisted for a median period of 23 months (range: 2-57). Five patients died after developing monocytosis (range: 20-188 months) and two experienced worsening disease and became transfusion dependent. Monocytosis was associated with increased white blood cells, decreased hemoglobin, decreased platelet count, and the presence of circulating blasts. In three cases, bone marrow biopsies after the onset of monocytosis showed marked myelomonocytic proliferation with morphological shifting from a typical primary myelofibrosis marrow appearance to aspects compatible with an overt 'secondary' chronic myelomonocytic leukemia. Before the development of monocytosis, 5 of 10 patients carried the JAK2V617F mutation; five patients showed karyotypic alterations. No change in JAK2 mutational status or cytogenetic evolution were associated with the development of monocytosis. Four of nine patients analyzed showed KRAS mutation in codon 12 or 13 with low allele burden. This is the first study correlating monocytosis developing in primary myelofibrosis patients with bone marrow morphology, laboratory data, molecular analysis and clinical follow-up. Development of monocytosis in patients with established primary myelofibrosis is associated with rapid disease progression and these patients should be considered as a high-risk group associated with short survival.

Stromal endothelial cells establish a bidirectional crosstalk with chronic lymphocytic leukemia cells through the TNF-related factors BAFF, APRIL, and CD40L.

Chronic lymphocytic leukemia (CLL) is a clonal B cell disorder of unknown origin. Accessory signals from the microenvironment are critical for the survival, expansion, and progression of malignant B cells. We found that the CLL stroma included microvascular endothelial cells (MVECs) expressing BAFF and APRIL, two TNF family members related to the T cell-associated B cell-stimulating molecule CD40L. Constitutive release of soluble BAFF and APRIL increased upon engagement of CD40 on MVECs by CD40L aberrantly expressed on CLL cells. In addition to enhancing MVEC expression of CD40, leukemic CD40L induced cleavases that elicited intracellular processing of pro-BAFF and pro-APRIL proteins in MVECs. The resulting soluble BAFF and APRIL proteins delivered survival, activation, Ig gene remodeling, and differentiation signals by stimulating CLL cells through TACI, BAFF-R, and BCMA receptors. BAFF and APRIL further amplified CLL cell survival by upregulating the expression of leukemic CD40L. Inhibition of TACI, BCMA, and BAFF-R expression on CLL cells; abrogation of CD40 expression in MVECs; or suppression of BAFF and APRIL cleavases in MVECs reduced the survival and diversification of malignant B cells. These data indicate that BAFF, APRIL, and CD40L form a CLL-enhancing bidirectional signaling network linking neoplastic B cells with the microvascular stroma.

Composite chronic lymphocytic leukemia/small lymphocytic lymphoma and follicular lymphoma are biclonal lymphomas: a report of two cases.

Composite lymphomas (CLs) consisting of 2 indolent B-cell lymphomas are rare. We present 2 CL cases composed of chronic lymphocytic leukemia (CLL) and follicular lymphoma (FL), each with unique clinicopathologic features. In the first case, the FL was negative for IGH-BCL2 and harbored a novel IGH-associated translocation; in the second case, the CL manifested in the skin. The individual components in both CLs were derived from different B-cell clones. This is the first complete characterization, including molecular analysis, of CLs composed of leukemic CLL and FL and the first report of a cutaneous CL derived from 2 low-grade B cell lymphomas. Our results provide additional supporting evidence that CLs of indolent B-cell lymphomas are biclonal and suggest that they are pathogenetically different from CLs composed of a low-grade B-cell lymphoma and an aggressive B-cell lymphoma or Hodgkin lymphoma, which are usually clonally related.

Splenic extramedullary hematopoietic proliferation in Philadelphia chromosome-negative myeloproliferative neoplasms: heterogeneous morphology and cytological composition.

We studied 24 spleens with extramedullary hematopoietic proliferation (EMHP), a key feature of advanced-stage Philadelphia chromosome-negative myeloproliferative neoplasms, obtained from 24 patients (14 primary myelofibrosis, 7 polycythemia vera and 3 unclassifiable). Hematoxylin and eosin, reticulin and trichrome stains, and immunohistochemical stains for myeloperoxidase, glycophorin-C, CD42b, CD34, CD117, CD8, nerve growth factor receptor and smooth muscle actin were evaluated. Clinical information was correlated with the morphological findings. Three distinct histological patterns of EMHP were recognized: diffuse (12), nodular (5), and mixed-nodular and diffuse (7). The preponderant lineage was granulocytic in diffuse, trilineage in nodular and erythroid in mixed EMHP. Erythropoiesis was largely intravascular, granulopoiesis was within the splenic cords and megakaryopoiesis was observed in both locations. The stromal changes paralleled the histological pattern with preservation of the splenic stromal and vascular architecture in the diffuse areas as opposed to areas of nodular EMHP. The morphological features of the splenic EMHP did not correlate with specific subtypes of myeloproliferative neoplasms. The mean duration of follow-up from initial diagnosis was 80 months. A total of 15 of the 24 patients died of disease: 8 of 12 (67%) with diffuse, 2 of 5 (40%) with nodular and 5 of 7 (71%) with mixed growth patterns. The mean duration from diagnosis to splenectomy was shorter in patients with diffuse (83 months) as compared with those with nodular EMHP (127 months). Our study demonstrates that splenic extramedullary hematopoietic proliferation in Philadelphia chromosome-negative myeloproliferative neoplasms shows distinct histological patterns that do not correlate with disease subtypes, but appear to suggest a trend between the histological patterns and clinical behavior. These results suggest a different biology of the disease in the nodular and diffuse extramedullary hematopoietic proliferation groups.

B cell-helper neutrophils stimulate the diversification and production of immunoglobulin in the marginal zone of the spleen.

Neutrophils use immunoglobulins to clear antigen, but their role in immunoglobulin production is unknown. Here we identified neutrophils around the marginal zone (MZ) of the spleen, a B cell area specialized in T cell-independent immunoglobulin responses to circulating antigen. Neutrophils colonized peri-MZ areas after postnatal mucosal colonization by microbes and enhanced their B cell-helper function after receiving reprogramming signals, including interleukin 10 (IL-10), from splenic sinusoidal endothelial cells. Splenic neutrophils induced immunoglobulin class switching, somatic hypermutation and antibody production by activating MZ B cells through a mechanism that involved the cytokines BAFF, APRIL and IL-21. Neutropenic patients had fewer and hypomutated MZ B cells and a lower abundance of preimmune immunoglobulins to T cell-independent antigens, which indicates that neutrophils generate an innate layer of antimicrobial immunoglobulin defense by interacting with MZ B cells.

Transformation of follicular lymphoma to plasmablastic lymphoma with c-myc gene rearrangement.

Follicular lymphoma (FL) is an indolent lymphoma that transforms to high-grade lymphoma, mostly diffuse large B-cell lymphoma, in about a third of patients. We present the first report of a case of FL that transformed to plasmablastic lymphoma (PBL). Clonal transformation of the FL to PBL was evidenced by identical IGH/BCL2 gene rearrangements and VDJ gene usage in rearranged IGH genes. IGH/ BCL2 translocation was retained in the PBL, which also acquired c-myc gene rearrangement. Genealogic analysis based on somatic hypermutation of the rearranged IGH genes of both FL and PBL suggests that transformation of the FL to PBL occurred most likely by divergent evolution from a common progenitor cell rather than direct evolution from the FL clone. Our study of this unusual case expands the histologic spectrum of FL transformation and increases our understanding of the pathogenetic mechanisms of transformation of indolent lymphomas to aggressive lymphomas.