Cutaneous epithelioid haemangiomas show somatic mutations in the mitogen-activated protein kinase pathway.

BACKGROUND: Epithelioid haemangioma (EH) arising from the skin is a benign vascular tumour with marked inflammatory cell infiltration, which exhibits a high tendency to persist and frequently recurs after resection. So far, the underlying pathogenesis is largely elusive. OBJECTIVES: To identify genetic alterations by next-generation sequencing and/or droplet digital polymerase chain reaction (ddPCR) in cutaneous EH. METHODS: DNA and RNA from an EH lesion of an index patient were subjected to whole-genome and RNA sequencing. Multiplex PCR-based panel sequencing of genomic DNA isolated from archival formalin-fixed paraffin-embedded tissue of 18 patients with cutaneous EH was performed. ddPCR was used to confirm mutations. RESULTS: We identified somatic mutations in genes of the mitogen-activated protein kinase (MAPK) pathway (MAP2K1 and KRAS) in cutaneous EH biopsies. By ddPCR we could confirm the recurrent presence of activating, low-frequency mutations affecting MAP2K1. In total, nine out of 18 patients analysed showed activating MAPK pathway mutations, which were mutually exclusive. Comparative analysis of tissue areas enriched for lymphatic infiltrate or aberrant endothelial cells, respectively, revealed an association of these mutations with the presence of endothelial cells. CONCLUSIONS: Taken together, our data suggest that EH shows somatic mutations in genes of the MAPK pathway which might contribute to the formation of this benign tumour.

SPARC-positive macrophages are the superior prognostic factor in the microenvironment of diffuse large B-cell lymphoma and independent of MYC rearrangement and double-/triple-hit status.

BACKGROUND: Diffuse large B-cell lymphoma (DLBCL) is a heterogeneous disease with respect to outcome. Features of the tumor microenvironment (TME) are associated with prognosis when assessed by gene expression profiling. However, it is uncertain whether assessment of the microenvironment can add prognostic information to the most relevant and clinically well-established molecular subgroups when analyzed by immunohistochemistry (IHC). PATIENTS AND METHODS: We carried out a histopathologic analysis of biomarkers related to TME in a very large cohort (n = 455) of DLBCL treated in prospective trials and correlated with clinicopathologic and molecular data, including chromosomal rearrangements and gene expression profiles for cell-of-origin and TME. RESULTS: The content of PD1+, FoxP3+ and CD8+, as well as vessel density, was not associated with outcome. However, we found a low content of CD68+ macrophages to be associated with inferior progression-free survival (PFS) and overall survival (OS; P = 0.023 and 0.040, respectively) at both univariable and multivariable analyses, adjusted for the factors of the International Prognostic Index (IPI), MYC break and BCL2/MYC and BCL6/MYC double-hit status. The subgroup of PDL1+ macrophages was not associated with survival. Instead, secreted protein acidic and cysteine rich (SPARC)-positive macrophages were identified as the subtype of macrophages most associated with survival. SPARC-positive macrophages and stromal cells directly correlated with favorable PFS and OS (both, P[log rank] <0.001, P[trend] < 0.001). The association of SPARC with prognosis was independent of the factors of the IPI, MYC double-/triple-hit status, Bcl2/c-myc double expression, cell-of-origin subtype and a recently published gene expression signature [lymphoma-associated macrophage interaction signature (LAMIS)]. CONCLUSIONS: SPARC expression in the TME detected by a single IHC staining with fair-to-good interobserver reproducibility is a powerful prognostic parameter. Thus SPARC expression is a strong candidate for risk assessment in DLBCL in daily practice.

[Aggressive B­cell lymphomas : Recommendations from the German Panel of Reference Pathologists in the Competence Network on Malignant Lymphomas on diagnostic procedures according to the current WHO classification, update 2017]. / Aggressive B­Zell-Lymphome : Empfehlungen des Deutschen Panels der Referenzpathologen im Kompetenznetz Maligne Lymphome e. V. zum diagnostischen Vorgehen nach der aktuellen WHO-Klassifikation, Update 2017.

The update of the 4th edition of the WHO classification for hematopoietic neoplasms introduces changes in the field of mature aggressive B­cell lymphomas that are relevant to diagnostic pathologists. In daily practice, the question arises of which analysis should be performed when diagnosing the most common lymphoma entity, diffuse large B­cell lymphoma. We discuss the importance of the cell of origin, the analysis of MYC translocations, and the delineation of the new WHO entities of high-grade B­cell lymphomas.

[Revised version of the 4th edition of the WHO classification of malignant lymphomas : What is new?] / Revidierte Fassung der 4. Ausgabe der WHO-Klassifikation maligner Lymphome : Was ist neu?

After 8 years, the WHO has now published the updated version of the 4th edition of the classification of hematopoietic and lymphoid tumors. This update provides a conceptual rewrite of existing entities as well as some new provisional entities and categories, particularly among the aggressive B­cell lymphomas. Important new diagnostic categories include the high-grade B­cell lymphomas, the large B­cell lymphoma with IRF4 rearrangement, and the Burkitt-like lymphoma with 11q aberrations. Of particular importance, new concepts concerning the taxonomy and classification of early lymphoid lesions or precursor lesions are included, such as the in situ follicular neoplasia or the in situ mantle cell neoplasia. In addition, the concept of indolent lymphoproliferations, such as breast-implant-associated anaplastic large cell lymphoma and the indolent T­cell lymphoproliferative disorder of the gastrointestinal tract, has been strengthened. Finally, diagnostic criteria for existing lymphoma entities have been refined.

Refractory or relapsed aggressive B-cell lymphoma failing (R)-CHOP: an analysis of patients treated on the RICOVER-60 trial.

BACKGROUND: The prognosis of elderly patients with aggressive B-non-Hodgkin's lymphoma after first lymphoma-related treatment failure (TF-L) is not well described. METHODS: We analysed patient characteristics including the presence of MYC rearrangements and MYC-expression immunohistochemistry (IHC) at diagnosis and modalities of salvage therapy and their impact on the prognosis of patients between 61 and 80 years who had been treated on the RICOVER-60 trial. RESULTS: TF-L occurred in 301 of the 1222 (24.6%) patients; 297 patients could be analysed. Prognosis was extremely poor in patients with primary progressive disease or early relapse (≤12 months) with median survivals of 3.3 and 6.4 months. Survival after TF-L was significantly lower in patients pretreated with R-CHOP compared with CHOP (23.0% versus 36.4% at 2 years, P = 0.016). In patients with MYC translocation at diagnosis Rituximab reduced the risk of TF-L from 58.8% to 26.3%. Survival after TF-L was significant longer for patients after CHOP without MYC translocations (31.8% versus 0% at 2 years, P < 0.001) or negative MYC-IHC (41.0% versus 16.8% at 2 years, P = 0.017) but not after R-CHOP. 224 patients (75.4%) received salvage therapy. Rituximab was part of salvage therapy in 57.4% and improved 2-year survival rate from 20.7% to 46.8% (P < 0.001). The benefit of R was significant after first-line CHOP [2-year overall survival (OS) 49.6% versus 19.1%, P < 0.001] as well as after R-CHOP (2-year OS 33.1% and 22.5%, P = 0.034). For patients pretreated with R-CHOP long-term survival was below 15% regardless of the treatment chosen. CONCLUSION: MYC rearrangement and IHC are adverse prognostic factors after TF-L for CHOP treated patients, rituximab as part of first-line therapy reduced the effects of MYC-break. Rituximab improves results of any type of salvage therapy; however, survival after progression/relapse of aggressive B-cell lymphoma in elderly patients pretreated with (R)-CHOP is poor regardless of treatment chosen.

Outcome of elderly patients with diffuse large B-cell lymphoma treated with R-CHOP: results from the UK NCRI R-CHOP14v21 trial with combined analysis of molecular characteristics with the DSHNHL RICOVER-60 trial.

BACKGROUND: There is an on-going debate whether 2- or 3-weekly administration of R-CHOP is the preferred first-line treatment for elderly patients with diffuse large B-cell lymphoma (DLBCL). The UK NCRI R-CHOP14v21 randomized phase 3 trial did not demonstrate a difference in outcomes between R-CHOP-14 and R-CHOP-21 in newly diagnosed DLBCL patients aged 19-88 years, but data on elderly patients have not been reported in detail so far. Here, we provide a subgroup analysis of patients ≥60 years treated on the R-CHOP14v21 trial with extended follow-up. PATIENTS AND METHODS: Six hundred and four R-CHOP14v21 patients ≥60 years were included in this subgroup analysis, with a median follow-up of 77.7 months. To assess the impact of MYC rearrangements (MYC-R) and double-hit-lymphoma (DHL) on outcome in elderly patients, we performed a joint analysis of cases with available molecular data from the R-CHOP14v21 (N = 217) and RICOVER-60 (N = 204) trials. RESULTS: Elderly DLBCL patients received high dose intensities with median total doses of ≥98% for all agents. Toxicities were similar in both arms with the exception of more grade ≥3 neutropenia (P < 0.0001) and fewer grade ≥3 thrombocytopenia (P = 0.05) in R-CHOP-21 versus R-CHOP-14. The elderly patient population had a favorable 5-year overall survival (OS) of 69% (95% CI: 65-73). We did not identify any subgroup of patients that showed differential response to either regimen. In multivariable analysis including individual factors of the IPI, gender, bulk, B2M and albumin levels, only age and B2M were of independent prognostic significance for OS. Molecular analyses demonstrated a significant impact of MYC-R (HR = 1.96; 95% CI: 1.22-3.16; P = 0.01) and DHL (HR = 2.21; 95% CI: 1.18-4.11; P = 0.01) on OS in the combined trial cohorts, independent of other prognostic factors. CONCLUSIONS: Our data support equivalence of both R-CHOP application forms in elderly DLBCL patients. Elderly MYC-R and DHL patients have inferior prognosis and should be considered for alternative treatment approaches. TRIAL NUMBERS: ISCRTN 16017947 (R-CHOP14v21); NCT00052936 (RICOVER-60).

[Blast-like tumor tissue in cervical lymph node with expression of placental alkaline phosphatase]. / Blastäres Tumorgewebe in Halslymphknoten mit Expression plazentaalkalischer Phosphatase.

We report a case of ALK1-positive anaplastic large cell lymphoma with expression of placental alkaline phosphatase (PLAP) in many tumor cells. Initially, due to the positivity of tumor cells for CD30 and PLAP, lymph node metastasis of a germ cell neoplasm was discussed. Anaplastic large cell lymphomas of T­cell lineage form a group of rare non-Hodgkin lymphomas with heterogeneous morphological and immunohistochemical appearance. They may imitate other neoplasms, such as large cell B­cell lymphomas, metastasis of a carcinoma, melanoma, embryonal carcinoma or seminoma, rhabdomyosarcoma and inflammatory myofibroblastic tumor. Only an extended immunohistochemistry panel leads to an accurate diagnosis.

Clinical, pathological and genetic features of follicular lymphoma grade 3A: a joint analysis of the German low-grade and high-grade lymphoma study groups GLSG and DSHNHL.

BACKGROUND: Histologically, follicular lymphoma (FL) grades 1, 2 and 3A are composed of two distinct cell types, centroblasts and centrocytes. FL grade 3B is composed only of centroblasts and has been shown to differ in immunophenotype and genetics from FL that contain centrocytes. We aimed to understand the pathogenetic and clinical relation between FL grade 3A to FL grade 1/2 on the one hand and FL grade 3B on the other hand. PATIENTS AND METHODS: Trial patients with long-term follow-up and diagnosis of FL grade 3 were selected and samples underwent a second central pathological review using a multiple-observer approach to assess grading. RESULTS: Interobserver variability for diagnosing FL grade 3 was high. FL grade 3A frequently harbored areas of FL grade 1/2 within the same tissue specimen. FL grade 3B rarely coexisted with grade 1/2 or 3A, suggesting divergent pathogenesis. There was no statistically significant difference in outcome between 47 cases of FL grade 3A and 14 cases of grade 3B. Compared with grade 1/2 FL, both groups showed longer progression-free survival without late events, especially after immunochemotherapy; this outcome difference was retained after adjustment for clinical prognostic factors. The subgroup of FL grade 3A with an additional FL grade 1/2 component or a translocation t(14;18) showed a poorer outcome. In contrast, the FL grade 3A lacking t(14;18) and of localized stage resembled the pediatric type of FL and showed a very good outcome. FL3 with MYC breaks showed a poor outcome. CONCLUSIONS: The results suggest that first-line immunochemotherapy might allow long-lasting remissions in a subgroup of FL grade 3A similar to diffuse large B-cell lymphoma. Within FL3A, prognostic subgroups can be identified by analyzing for coexisting FL1/2 and MYC breaks.

Phosphorylated epidermal growth factor receptor expression and KRAS mutation status in salivary gland carcinomas.

OBJECTIVES: Salivary gland carcinomas (e.g., adenoidcystic carcinoma or mucoepidermoid carcinoma) are rare and often unresectable head and neck tumors. They are also weakly affected by most chemotherapeutic drugs, which emphasize the need for further studies on this topic. In clinical practice, various drugs target the well-characterized EGFR pathway in many epithelial tumors. There is limited reliable data on phophorylated EGFR expression, such as activated conformation, in salivary gland tumors. MATERIALS AND METHODS: This study investigates the pEGFR expression in salivary gland carcinomas (n = 43). Three different carcinoma varieties, that represent >50 % of all salivary gland tumors, were included: adenoidcystic carcinoma (n = 23), mucoepidermoid carcinoma (n = 17), and adenocarcinoma NOS (not otherwise specified) (n = 3). The specimens were investigated by immunohistochemistry. Additionally, mutations of KRAS oncogene were screened with gene sequencing. The findings were correlated with clinical data by using SPSS. RESULTS: In 34 out of 43 specimens (79 %), a positive staining for pEGFR was found. Sex, tumor entity, tumor site, and grading had no significant correlation with pEGFR expression. A weak correlation was found for tumor size and pEGFR expression. Significant correlations were found for pEGFR expression with patient's age and lymph node metastasis (pN). No specimen showed a KRAS mutation in codon 12 or 13. CONCLUSION: Salivary gland carcinomas show a high expression of pEGFR. This high expression correlates with lymph node metastasis, which supports the hypothesis that a high pEGFR expression facilitates lymphogenous metastasis. Due to this pEGFR expression, status may be a negative predictive factor in salivary gland carcinoma diagnostics. Patients with pN-positive salivary gland cancer may benefit from EGFR-inhibiting drugs. CLINICAL RELEVANCE: The EGFR pathway may be a potential target for chemotherapy of advanced unresectable salivary gland carcinomas.

[Mediastinal lymphomas]. / Lymphome des Mediastinums.

Lymphomas infiltrating the mediastinum are a challenge for the treating physician as well as for the pathological diagnostics. The clinical scenario is often an emergency situation, while the pathologist is usually confronted only with small biopsy samples. Classical Hodgkin's lymphoma is by far the most frequently occurring lymphoma in the mediastinum and predominantly the nodular sclerosis subtype. In small and very sclerotic specimens it can be difficult to morphologically detect Hodgkin and Reed-Sternberg cells and to identify the characteristic phenotype by immunohistochemistry. Primary mediastinal large B­cell lymphomas should be distinguished from classical Hodgkin's lymphomas as the treatment is different. This is characterized by the detection of sheets of blast cells, which immunohistochemically show a strong B­cell phenotype (positivity for CD20 and CD79a), while CD30 can also often be expressed. The intimate biological relationship between classical Hodgkin's lymphomas and mediastinal large B­cell lymphomas is illustrated by the existence of B­cell lymphomas with intermediate features (so-called mediastinal grey zone lymphomas). It is important to recognize and diagnose these lymphomas as they are associated with a slightly inferior prognosis. Extranodal thymic marginal zone lymphomas of the mucosa-associated lymphoid tissue (MALT) type are a rare form of lymphoma encountered in the mediastinum, which can be associated with autoimmune diseases. T­lymphoblastic lymphomas and leukemia, which occur predominantly in children and young adults, represent a rapidly growing precursor cell neoplasia and must be distinguished from thymomas in the differential diagnostics as well as from normal and hyperplastic thymus glands.

CD68 expression is a discriminative feature of indolent cutaneous CD8-positive lymphoid proliferation and distinguishes this lymphoma subtype from other CD8-positive cutaneous lymphomas.

BACKGROUND: Indolent cutaneous CD8+ lymphoid proliferation is a recently described rare entity among cutaneous T-cell lymphomas that typically presents with solitary skin lesions at acral sites. Separation from otherwise aggressive T-cell lymphomas bearing a cytotoxic CD8+ phenotype is fundamental to avoid unnecessary harmful treatment. However, up to now, no reliable discriminative marker has been identified. OBJECTIVES: Motivated by these diagnostic quandaries, we have analyzed a large series of archived formalin-fixed paraffin-embedded (FFPE) specimens of atypical CD8+ cutaneous infiltrates with clear-cut diagnosis and clinical follow-up (n = 44) including five cases of indolent CD8+ lymphoid proliferation by using immunohistochemistry with the aim of obtaining markers predictive of subtype assignment. RESULTS: We identified exclusive expression of CD68 by lymphoma cells within the subgroup of indolent CD8+ lymphoid proliferation (5/5 cases). Specific CD68 expression in this entity was confirmed by the application of several monoclonal antibodies (KP1, PG-M1, KiM1P) against the CD68 molecule available for FFPE tissue. In contrast, none of the infiltrates of the other CD8+ cutaneous lymphoma entities stained positive for CD68 (0/39). CONCLUSIONS: Based on these observations, we suggest CD68 as a new discriminative marker which is helpful in distinguishing indolent CD8+ lymphoid proliferation from other CD8+ cutaneous lymphomas in ambiguous cases.

CHO(E)P-14 followed by alemtuzumab consolidation in untreated peripheral T cell lymphomas: final analysis of a prospective phase II trial.

The rate of long-term remissions after treatment of peripheral T cell lymphomas (PTCL) with standard CHOP-like protocols is unsatisfactory. A prospective multicenter phase II trial was initiated in untreated patients with PTCL of all International Prognostic Index-risk groups, evaluating alemtuzumab consolidation in patients with complete or good partial remission after CHO(E)P-14 induction. Twenty-nine (70.7 %) of the 41 enrolled patients received alemtuzumab consolidation (133 mg in total). The main grades 3-4 toxicities during alemtuzumab therapy were infections and neutropenia with one potentially treatment-related death. Complete responses were seen in 58.5 %, partial responses in 2.4 % and 29.3 % had progressive disease. After a median observation time of 46 months, 19 patients have died, 16 of them due to lymphoma and/or salvage therapy complications. Event-free and overall survival at 3 years in the whole intent to treat population are 32.3 and 62.5 %, respectively, and 42.4 and 75.1 % in the patients who received alemtuzumab. In conclusion, application of a short course of alemtuzumab after CHO(E)P-14 induction is feasible although complicated by severe infections. A current phase III trial, applying alemtuzumab as part of the initial chemotherapy protocol to avoid early progression, will further clarify its significance for the therapeutic outcome.

[Grey zone lymphomas: limitations of the classification of aggressive B-cell lymphomas]. / Grauzonenlymphome : Grenzbereiche der Klassifikation aggressiver B-Zell-Lymphome.

Grey zone lymphomas are lymphatic tumors that cannot be assigned to a defined lymphoma entity due to morphological, clinical or genetic reasons. As a defining criterion they present with features of two overlapping entities or features that are intermediate. Such lymphomas may represent a grey zone in the differentiation between indolent and aggressive lymphomas. Often they may show morphological features of one entity but be more related to another entity with respect to the immunophenotype and/or genetic constitution, such as lymphomas in the grey zone between primary mediastinal large B-cell lymphoma and primary nodal diffuse large B-cell lymphoma. The B-cell lymphoma, unclassified, with features intermediate between diffuse large B-cell lymphoma and Burkitt lymphoma has recently been recognized as a provisional category in the updated WHO 2008 classification of malignant lymphomas. This corresponds to a practical lymphoma category that obviously contains several entities with a Burkitt-like appearance and aggressive clinical behavior. Genetically, tumors in this category are frequently characterized by an atypical MYC translocation and complex karyotypic alterations. As yet, no adequate therapy concept exists.

[Round robin test for detection of genomic aberrations in non-Hodgkin lymphoma by in situ hybridization]. / Ringversuch zum Nachweis genomischer Veränderungen bei Non-Hodgkin-Lymphomen mittels In-situ-Hybridisierung.

BACKGROUND: The detection of characteristic genomic aberrations by fluorescence in situ hybridization (FISH) has a high diagnostic impact on lymphomas according to the World Health Organization (WHO). To investigate the reproducibility of non-isotopic ISH results a multicenter trial was carried out involving eight institutes for hematopathology. MATERIAL AND METHODS: Analyses were performed on two diffuse large B-cell lymphomas (DLBCL) without known aberrations, on one follicular lymphoma with a IGH/BCL2 translocation and BCL6 split and on two B-cell lymphomas intermediate between DLBCL and Burkitt's lymphoma with c-MYC and BCL2 rearrangements, one with an additional BCL6 split. Break-apart probes for BCL6 and c-MYC, as well as fusion probes for the c-MYC/IGH and the IGH/BCL2 translocations were used. RESULTS: All aberrations were correctly detected by all centres and no false positive or false negative results were obtained. The numbers of positive cells varied from 25% to 94%. Pearson's correlation coefficient between the centres was always > 0.8. CONCLUSIONS: The ISH analysis of recurrent genomic aberrations in formalin-fixed paraffin-embedded (FFPE) tissue is a highly reproducible technique which yields substantial additive help for lymphoma diagnostics.

Gene expression and copy number profiling of follicular lymphoma biopsies from patients treated with first-line rituximab without chemotherapy.

The Nordic Lymphoma Study Group has performed two randomized clinical trials with chemotherapy-free first-line treatment (rituximab +/- interferon) in follicular lymphoma (FL), with 73% of patients alive and 38% without any need of chemotherapy after 10.6 years median follow-up. In order to identify predictive markers, that may also serve as therapeutic targets, gene expression- and copy number profiles were obtained from 97 FL patients using whole genome microarrays. Copy number alterations (CNAs) were identified, e.g. by GISTIC. Cox Lasso Regression and Lasso logistic regression were used to determine molecular features predictive of time to next therapy (TTNT). A few molecular changes were associated with TTNT (e.g. increased expression of INPP5B, gains in 12q23/q24), but were not significant after adjusting for multiple testing. Our findings suggest that there are no strong determinants of patient outcome with respect to GE data and CNAs in FL patients treated with a chemotherapy-free regimen (i.e. rituximab +/- interferon).

Stromal gene signatures in large-B-cell lymphomas.

BACKGROUND: The addition of rituximab to combination chemotherapy with cyclophosphamide, doxorubicin, vincristine, and prednisone (CHOP), or R-CHOP, has significantly improved the survival of patients with diffuse large-B-cell lymphoma. Whether gene-expression signatures correlate with survival after treatment of diffuse large-B-cell lymphoma is unclear. METHODS: We profiled gene expression in pretreatment biopsy specimens from 181 patients with diffuse large-B-cell lymphoma who received CHOP and 233 patients with this disease who received R-CHOP. A multivariate gene-expression-based survival-predictor model derived from a training group was tested in a validation group. RESULTS: A multivariate model created from three gene-expression signatures--termed "germinal-center B-cell," "stromal-1," and "stromal-2"--predicted survival both in patients who received CHOP and patients who received R-CHOP. The prognostically favorable stromal-1 signature reflected extracellular-matrix deposition and histiocytic infiltration. By contrast, the prognostically unfavorable stromal-2 signature reflected tumor blood-vessel density. CONCLUSIONS: Survival after treatment of diffuse large-B-cell lymphoma is influenced by differences in immune cells, fibrosis, and angiogenesis in the tumor microenvironment.

Lacking CD56 expression in a relapsing cutaneous blastic plasmacytoid dendritic cell neoplasm after allogeneic bone marrow transplantation: FISH analysis revealed loss of 11q.

BACKGROUND: Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare entity characterized by a CD4+/CD56+/CD123+ immunophenotype and a fatal clinical course. The average survival of 12-14 months may be prolonged by allogeneic bone marrow transplantation (BMT). OBJECTIVES: We report about a male patient who suffered from BPDCN with a typical histology and co-expression of CD4/CD123 and a CD56 expression by 80% of the tumour cells. The cutaneous tumour relapse after chemotherapy and allogeneic BMT was completely negative for CD56. METHODS: We performed interphase fluorescence in situ hybridization (FISH) analysis of tumour tissue, asserved before and after BMT, using specific probes for chromosome 11, which encompass the CD56 gene region. RESULTS: The tumour cells revealed a partial loss of 11q as well as a monosomy of chromosome 11. CONCLUSION: This case demonstrates for the first time that loss of CD56 expression can also occur as a secondary event after chemotherapy and BMT. In our case, DNA loss of 11q23 could be responsible for the negativity of 20% of tumour cells as observed before chemotherapy. However, the complete loss of CD56 expression in the relapsed tumour cannot be explained by the loss of 11q23 alone. Additional factors such as chemotherapy-induced mutations might also have contributed.

Relation of gene expression phenotype to immunoglobulin mutation genotype in B cell chronic lymphocytic leukemia.

The most common human leukemia is B cell chronic lymphocytic leukemia (CLL), a malignancy of mature B cells with a characteristic clinical presentation but a variable clinical course. The rearranged immunoglobulin (Ig) genes of CLL cells may be either germ-line in sequence or somatically mutated. Lack of Ig mutations defined a distinctly worse prognostic group of CLL patients raising the possibility that CLL comprises two distinct diseases. Using genomic-scale gene expression profiling, we show that CLL is characterized by a common gene expression "signature," irrespective of Ig mutational status, suggesting that CLL cases share a common mechanism of transformation and/or cell of origin. Nonetheless, the expression of hundreds of other genes correlated with the Ig mutational status, including many genes that are modulated in expression during mitogenic B cell receptor signaling. These genes were used to build a CLL subtype predictor that may help in the clinical classification of patients with this disease.