Lymphomatoid papulosis types D and E: a multicentre series of the French Cutaneous Lymphomas Study Group.

BACKGROUND: Lymphomatoid papulosis (LyP) type D (LyP D) and type E (LyP E) have recently been described in small series of cases or isolated case reports. AIM: To further describe the clinical and histological features of LyP D and E based on a retrospective multicentre study. METHODS: The clinical and histopathological features of 29 patients with an initial diagnosis of LyP D or LyP E were retrospectively assessed using standardized forms. RESULTS: After exclusion of 5 cases, 24 patients (14 LyP D, 10 LyP E) were enrolled in the study. The median follow-up was 2.5 years (range 1 month to 13 years). LyP D was characterized by multiple recurrent self-regressing small papules that developed central erosion or necrosis, whereas LyP E presented as papulonodular lesions that rapidly evolved into necrotic eschar-like lesions > 10 mm in size. Epidermal changes were more frequent in LyP D, whereas dermal infiltrates were deeper in LyP E. Anaplastic cytology was rare and the DUSP22 rearrangement was never observed. Two patients (8%) had an associated cutaneous lymphoma. CONCLUSION: LyP D and E have distinct clinical findings and may be associated with other cutaneous lymphomas.

Clinical and molecular characteristics of non-small-cell lung cancer (NSCLC) harboring EGFR mutation: results of the nationwide French Cooperative Thoracic Intergroup (IFCT) program.

BACKGROUND: EGFR mutations cause inconsistent response to EGFR tyrosine-kinase inhibitors (TKI). To better understand these features, we reviewed all cases of EGFR-mutated non-small-cell lung cancer collected in the Biomarkers France database. PATIENTS AND METHODS: Of 17 664 patients, 1837 (11%) with EGFR-mutated non-small-cell lung cancer were retrospectively analyzed for clinical and molecular characteristics. Results were correlated with survival and treatment response for the 848 stage IV patients. RESULTS: EGFR exon 18, 19, 20 and 21 mutations were found in 102 (5.5%), 931 (51%), 102 (5.5%) and 702 (38%) patients, respectively. Over 50% of exon 18 and 20 mutated patients were smokers. The median follow-up was 51.7 months. EGFR mutation type was prognostic of overall survival (OS) versus wild-type {exon 19: hazard ratio (HR)=0.51 [95% confidence interval (CI): 0.41-0.64], P < 0.0001; exon 21: HR = 0.76 (95% CI: 0.61-0.95), P = 0.002; exon 20: HR = 1.56 (95% CI: 1.02-2.38), P = 0.004}. EGFR mutation type was prognostic of progression-free survival versus wild-type [exon 19: HR = 0.62 (95% CI: 0.49-0.78), P < 0.0001; exon 20: HR = 1.46 (95% CI: 0.96-2.21), P = 0.07]. First-line treatment choice did not influence OS in multivariate analysis. First-line TKI predicted improved progression-free survival versus chemotherapy [HR = 0.67 (95% CI: 0.53-0.85), P = 0.001]. OS was longer for del19 versus L858R, which was associated with better OS compared with other exon 21 mutations, including L861Q. TKI improved survival in patients with exon 18 mutations, while chemotherapy was more beneficial for exon 20-mutated patients. CONCLUSION: EGFR mutation type can inform the most appropriate treatment. Therapeutic schedule had no impact on OS in our study, although TKI should be prescribed in first-line considering the risk of missing the opportunity to use this treatment.

Assessment of diagnostic criteria between primary cutaneous anaplastic large-cell lymphoma and CD30-rich transformed mycosis fungoides; a study of 66 cases.

BACKGROUND: Transformed mycosis fungoides (TMF) large cells may express CD30 antigen, and because of this, the differential diagnosis between CD30-rich TMF and primary cutaneous anaplastic large-cell lymphoma (cALCL) may be difficult, and especially in distinguishing cALCL associated with MF vs. CD30-rich TMF. OBJECTIVES: To find clinical, histological and molecular diagnostic features useful for differential diagnosis between cALCL and CD30-rich TMF. To analyse and compare the prognostic value of clinical and pathological factors in these two diseases. MATERIAL AND METHODS: We conducted a retrospective study (1999-2012) of 32 patients with cALCL and 34 with CD30-rich TMF, seen in reference centres of the French Study Group of Cutaneous Lymphoma. Clinical, histological and molecular features were analysed and compared to determine their diagnostic and prognostic value. RESULTS: Comparison of the two groups showed that age ˃ 60 years, ≥ 5 skin lesions, early progression, absence of spontaneous regression and trunk involvement were significantly associated with the diagnosis of TMF. Abnormal T-cell phenotype and perforin expression were significantly more frequent in cALCL (both P < 0·001). Overall survival (OS) at 5 years was 77·4% for cALCL and 20·7% for CD30-rich TMF. Stage T3, ≥ 5 skin lesions, lower limb involvement for cALCL and stage T4, extracutaneous involvement, B symptoms, high levels of lactate dehydrogenase for CD30-rich TMF were associated with poor OS and progression-free survival. DUSP22 gene rearrangement had no diagnostic or prognostic value. CONCLUSIONS: Clinical features and outcome are the most discriminative to differentiate the two entities. Even histological and molecular markers were not fully specific; abnormal vs. normal T-cell phenotype and perforin expression may constitute helpful tools.

Diagnostic value of immunohistochemistry for the detection of the BRAFV600E mutation in primary lung adenocarcinoma Caucasian patients.

BACKGROUND: Non-small-cell lung carcinoma (NSCLC) patients with a BRAF(V600E) mutation benefit from targeted therapy. The usefulness of immunohistochemistry (IHC) as an alternative approach for the detection of BRAF(V600E) in NSCLC patients has not been evaluated until now. This study compared the specificity and sensitivity of IHC with other methods for the detection of BRAF(V600E) in primary lung adenocarcinoma. PATIENTS AND METHODS: BRAF mutations were analysed by DNA sequencing of a Caucasian subpopulation of selected 450 of 1509 (30%) EGFR, KRAS, PI3KA, Her2 and EML4-ALK wild-type (wt) primary lung adenocarcinomas. Detection of the BRAF(V600E) mutation was carried out by IHC using the VE1 clone antibody and compared with the results of other molecular methodologies. RESULTS: Of 450 (9%) of tumours, 40 harboured a BRAF mutation, which corresponded to either a BRAF(V600E) or a non-BRAF(V600E) mutation in 21 of 450 (5%) and 19 of 450 (4%) cases, respectively. The IHC VE1 assay was positive in 19 of 21 (90%) BRAF(V600E)-mutated tumours and negative in all BRAF(nonV600E)-mutated tumours. CONCLUSION: IHC using the VE1 clone is a specific and sensitive method for the detection of BRAF(V600E) and may be an alternative to molecular biology for the detection of mutations in NSCLC.

Cell cycle arrest and p53 prevent ON-target megabase-scale rearrangements induced by CRISPR-Cas9.

The CRISPR-Cas9 system has revolutionized our ability to precisely modify the genome and has led to gene editing in clinical applications. Comprehensive analysis of gene editing products at the targeted cut-site has revealed a complex spectrum of outcomes. ON-target genotoxicity is underestimated with standard PCR-based methods and necessitates appropriate and more sensitive detection methods. Here, we present two complementary Fluorescence-Assisted Megabase-scale Rearrangements Detection (FAMReD) systems that enable the detection, quantification, and cell sorting of edited cells with megabase-scale loss of heterozygosity (LOH). These tools reveal rare complex chromosomal rearrangements caused by Cas9-nuclease and show that LOH frequency depends on cell division rate during editing and p53 status. Cell cycle arrest during editing suppresses the occurrence of LOH without compromising editing. These data are confirmed in human stem/progenitor cells, suggesting that clinical trials should consider p53 status and cell proliferation rate during editing to limit this risk by designing safer protocols.

CRISPR-Cas9 globin editing can induce megabase-scale copy-neutral losses of heterozygosity in hematopoietic cells.

CRISPR-Cas9 is a promising technology for gene therapy. However, the ON-target genotoxicity of CRISPR-Cas9 nuclease due to DNA double-strand breaks has received little attention and is probably underestimated. Here we report that genome editing targeting globin genes induces megabase-scale losses of heterozygosity (LOH) from the globin CRISPR-Cas9 cut-site to the telomere (5.2 Mb). In established lines, CRISPR-Cas9 nuclease induces frequent terminal chromosome 11p truncations and rare copy-neutral LOH. In primary hematopoietic progenitor/stem cells, we detect 1.1% of clones (7/648) with acquired megabase LOH induced by CRISPR-Cas9. In-depth analysis by SNP-array reveals the presence of copy-neutral LOH. This leads to 11p15.5 partial uniparental disomy, comprising two Chr11p15.5 imprinting centers (H19/IGF2:IG-DMR/IC1 and KCNQ1OT1:TSS-DMR/IC2) and impacting H19 and IGF2 expression. While this genotoxicity is a safety concern for CRISPR clinical trials, it is also an opportunity to model copy-neutral-LOH for genetic diseases and cancers.

PTEN, ATM, IDH1 mutations and MAPK pathway activation as modulators of PFS and OS in patients treated by first line EGFR TKI, an ancillary study of the French Cooperative Thoracic Intergroup (IFCT) Biomarkers France project.

OBJECTIVES: Tumor mutation screening is standard of care for patients with stage IV NSCLC. Since a couple of years, widespread NGS approaches used in routine diagnostics to detect driver mutations such as EGFR, KRAS, BRAF or MET allows the identification of other alterations that could modulated the intensity or duration of response to targeted therapies. The prevalence of co-occurring alterations that could affect response or prognosis as not been largely analyzed in clinical settings and large cohorts of patients. Thanks to the IFCT program "Biomarkers France", a collection of samples and data at a nation-wide level was available to test the impact of co-mutations on first line EGFR TKI in patients with EGFR mutated cancers. MATERIALS AND METHODS: Targeted NGS was assessed on available (n = 208) samples using the Ion AmpliSeq™ Cancer Hotspot Panel v2 to screen for mutations in 50 different cancer genes. RESULTS: This study showed that PTEN inactivating mutations, ATM alterations, IDH1 mutations and complex EGFR mutations were predictors of short PFS in patients with a stage 4 lung adenocarcinoma receiving first line EGFR TKI and that PTEN, ATM, IDH1 and KRAS mutations as well as alterations in the MAPK pathway were related to shorter OS. CONCLUSION: These findings may lead to new treatment options in patients with unfavorable genotypes to optimize first line responses.

[Management of cutaneous T-cell lymphomas: Recommendations of the French Cutaneous Lymphoma Group]. / Prise en charge des lymphomes T cutanés : recommandations du Groupe français d'étude des lymphomes cutanés.

BACKGROUND: Classification of diagnostic methods, of initial staging and of the treatment of primary cutaneous T-cell lymphomas, particularly the most common epidermotropic forms, constitutes an essential step in rationalising therapeutic practice and in evaluating the results of treatment. PATIENTS AND METHODS: We carried out an analysis of the literature and of existing recommendations in order to create recommendations regarding the diagnosis, initial staging and treatment of primary T-cell lymphomas. RESULTS: We present the key elements of diagnosis and initial staging. The selected therapeutic strategy, which necessarily changes over time, must avoid both unnecessarily aggressive early treatment as well as an overly timid therapeutic approach that could allow lesions to rapidly progress towards more advanced stages. Regular reassessment of the benefit/risk ratio is necessary and involves the use of first- and second-line measures, in which it is difficult to establish any hierarchy, with the current tendency favouring in particular combined therapy as second-line treatment in order to limit the toxicity of each individual constituent drug within the combination. The creation of a national SPC marks significant progress in difficult cases. CONCLUSION: As a result of the offer, limited level of proof in existing studies, which are generally unsatisfactory in terms of methodology, the new recommendations described herein are timely and should be updated regularly in accordance with advances in knowledge. The organisation of clinical trials and validation of the scoring systems currently being developed should be encouraged.

Increased production of the TrkB protein tyrosine kinase receptor after brain insults.

The protein-tyrosine kinases Trk, TrkB, and TrkC are signal-transducing receptors for a family of neurotrophic factors known as the neurotrophins. Here we show that seizures induced by hippocampal kindling lead to a rapid, transient increase of trkB mRNA and protein in the hippocampus. TrkB is a component of a high affinity receptor for brain-derived neurotrophic factor (BDNF). No change was detected in mRNAs for Trk or TrkC, components of the high affinity nerve growth factor or neurotrophin-3 receptors, respectively. trkB mRNA was also transiently increased in the dentate gyrus following cerebral ischemia and hypoglycemic coma; these treatments had no effect on trk and trkC mRNAs. The increase in trkB mRNA and protein showed the same time course and distribution as the increase in BDNF mRNA. These data suggest that BDNF and its receptor may play a local role within the hippocampus in kindling-associated neural plasticity and in neuronal protection following epileptic, ischemic, and hypoglycemic insults.

[Optimized protocols for interphase FISH analysis of imprints and sections using split signal probes]. / Application de la technique de FISH interphasique avec des sondes encadrantes dites de <> à différents types de préparations histologiques et cytologiques.

Fluorescent in situ hybridization (FISH) analysis is a molecular technique allowing the detection of recurrent translocations in cancer. Several hybridization protocols were assayed in order to evaluate their performances for interphase FISH analysis of histological sections and imprints using split probes. Adult and foetal lymphoid tissues were selected. Touch imprints of fresh (EF) or frozen (EC) tissues, sections (CF) and isolated nuclei (NI) of formol-fixed paraffin-embedded tissues were performed. The cut-off values of the IGH, IGlambda, BCL-2, BCL-6, CCND1 and MYC DNA FISH split signal probes were calculated for adult reactive lymph nodes on the different histological preparations (EC, CF, CC, NI) and on several tissues for the IGH and BCL-6 probes. In reactive lymph nodes, the cut-off values of the probes were between 3 and 13% and found independent of the preparation type. Conversely, slight but significant variations of the cut-off level were observed when different foetal control tissues were assayed with the same probe set. Finally, this study provided optimized-protocols for FISH analysis of either fresh/frozen imprints or formalin-fixed paraffin-embedded sections using split signal DNA probes.

Splitting bone marrow trephines into frozen and fixed fragments allows parallel histological and molecular detection of B cell malignant infiltrates.

Clonality analysis of the immunoglobulin heavy chain (IgH) gene is helpful in identifying malignant B cell infiltrates in the bone marrow and is usually carried out on separate aspirates or on the same formalin-fixed decalcified bone marrow specimen. To determine whether the removal of the decalcification step would improve the molecular analysis, we first studied 12 bone marrow specimens with lymphoma infiltration split into a fixed and a small frozen fragment. Both the detection rate of IgH gene monoclonality and DNA quality were found to be superior in the frozen part than in the fixed part. Conversely, to evaluate whether the split would compromise histological analysis, we selected a series of 134 bone marrow specimens obtained from patients with small B cell lymphoma and showing IgH monoclonality on the frozen part. The histological detection rate of infiltrated or suspicious infiltrates (95%) on the fixed part was not altered by saving a frozen part.

Improved transfection using epithelial cell line-selected ligands and fusogenic peptides.

Synthetic gene transfer vectors can be optimised by combining DNA-binding peptides, cell surface receptor ligands, and fusogenic and nuclear localisation peptides. We have used the phage display technique to identify ligands of the tracheal epithelial cell line CFT-2. The peptides harboured by two phages were selected for transfection studies: peptide 7 (GRGDGDV) that contained the integrin-binding motif RGD, and peptide 9 (RFDSLKV) that was found in six out of 24 phages analysed. Both peptides, fused with the DNA-binding peptide P2 (SPKRSPKRSPKR), enhanced transfection efficiency in cell lines CFT-2, NT-1, NIH-3T3 and ECV-304. In particular, peptide P2-7 increased transfection efficiency from 36. 5% to 44.8% in NIH-3T3 cells and from 10.9% to 14.4% in CFT-2 cells, when compared to transfections performed with peptide P2. Two fusogenic peptides, HA (GLFEAIAEFIEGGWEGLIEGC) and JTS-1 (GLFEALLELLESLWELLLEA), were then added to the complexes and shown to improve transfection efficiency to the same extent. For instance, when combined to peptide P2-7, transfection levels of 54.1% and 55. 2% were attained in NIH-3T3 cells with HA and JTS-1, respectively. The addition of the ligands and fusogenic peptides thus allowed us to construct greatly improved transfection reagents.

Evidence that an identical T cell clone in skin and peripheral blood lymphocytes is an independent prognostic factor in primary cutaneous T cell lymphomas.

The monoclonality of the T cell receptor gamma-chain gene was analyzed by polymerase chain reaction in skin and blood specimens of 85 patients with cutaneous T cell lymphomas including 67 mycosis fungoides, seven Sézary syndromes, and 11 CD30- nonepidermotropic cutaneous T cell lymphomas. A cutaneous T cell clone was detected in 69% of mycosis fungoides and 100% of Sézary syndromes. This frequency varied according to the clinical stage: 57% in early stages (Ia-IIa) to 96% in advanced stages (IIb-IV, Sézary syndrome). A peripheral blood T cell clone was detected in 42% of early stages and in 74% of late stages but was identical to the cutaneous one in 15% and in 63%, respectively. A significant association between initial clinical stage and T cell monoclonality was observed. In nonepidermotropic cutaneous T cell lymphomas, T cell monoclonality was detected in 55% of skin and 36% of blood samples. Univariate and multivariate analyses showed that, besides the initial clinical stage, an identical cutaneous and blood T cell clone was an independent prognostic factor for disease progression of mycosis fungoides/Sézary syndrome (hazard ratio 3.4, 95% confidence interval 1.4-9.9). Parallel polymerase chain reaction study of skin and blood specimens may therefore provide an initial prognostic marker that could help to monitor therapeutic strategies. A fully prospective study, with simultaneous therapeutic trials, needs to be done to confirm our findings and to include treatment variables in the statistical analysis.

Telomerase activity in human thyroid carcinomas originating from the follicular cells.

Telomerase activity is known to be absent from most normal and well-differentiated tissues, although being detectable in the vast majority of malignant tumors. An increasing number of reports demonstrate that telomerase may be activated in benign tumors, such as adenomas. We have investigated a series of normal and neoplastic thyroid tissues for the presence of telomerase activity. As expected, all normal thyroid tissues (n = 20) had no display of telomerase activity. Amongst cancers, the incidence of telomerase activity varied with the histological subtypes. Telomerase activity was present in only 3/15 cases (20%) of papillary carcinomas. Telomerase activity was more frequently detected in follicular (4/6) and in undifferentiated (2/3) carcinomas. Unexpectedly, one case (1/12) of adenoma contained high levels of telomerase activity. Taken together, these results indicate that telomerase may play some role in the pathogenesis of thyroid tumors, in particular in follicular and undifferentiated carcinomas that are known to have the most aggressive behavior.

Detection of circulating cells expressing chromogranin A gene transcripts in patients with lung neuroendocrine carcinoma.

High grade lung neuroendocrine carcinomas, like small and large cell neuroendocrine carcinomas, pose therapeutic problems. Most initially respond to chemotherapeutic agents, but early relapses are frequent and are resistant to the presently available treatments. Our study reports for the first time the development and evaluation of a test for detecting the presence of circulating tumour cells by measuring chromogranin A gene transcripts with reverse transcriptase-polymerase chain reaction (RT-PCR) and Southern blotting. The test is specific and sensitive (detection of 10 cancer cells/ml blood), and only minimally invasive. Positivity is statistically correlated to high grade neuroendocrine carcinomas and to a poor prognosis with a 3-fold higher lethal risk. The test now needs to be assessed for its usefulness as a tool in the initial staging procedures and follow-up by comparison with the recent immunoradiometric assay (RIA) for detection of chromogranin A in the serum.

Primary extramedullary plasmacytoma of the liver. A case report.

We report the first case of primary extramedullary plasmacytoma of the liver. The tumor was situated in segment VIII of the liver without extrahepatic extension. Histologically, the tumor was composed of sheets of mature plasma cells with slight atypia in association with proplasmacytes invading the hepatic parenchyma. Neither plasmoblasts nor lymphoplasmacytes were present. Immunohistochemistry demonstrated monoclonal IgG and kappa light-chain expression. In situ hybridization confirmed the monotypic expression of kappa light-chain mRNA. Bone marrow examination revealed no abnormality. After surgery, the IgG kappa spike detected in preoperative plasma samples decreased. The patient is disease free 31 months postoperatively.

Cystic smooth-muscle tumor of the liver and spleen associated with Epstein-Barr virus after renal transplantation.

Immunosuppression is known to favor the development of various types of tumors. After organ transplantation, the risk of lymphoproliferative disease, whether clonal or not, is particularly increased and clearly associated with Epstein-Barr virus infection. We report a case of an unusual large cystic tumor of the liver with satellite hepatic and splenic nodules occurring 4 years after renal transplantation. Radiologic examination showed a rich vascularization of the tumor. Light and electron microscopy of a surgical liver biopsy, completed by an immunohistochemical study, demonstrated a well-differentiated tumor of smooth-muscle origin. Using in situ hybridization, we showed large amounts of Epstein-Barr virus messenger RNAs within the tumor cells. In addition, Southern blot analysis revealed that viral DNA was present in the form of a single monoclonal episome within the tumor. The polymerase chain reaction analysis of the genomic DNA of tumoral cells also indicated a monoclonal pattern. At last, the tumor was shown to be of host origin. Six months later, and despite three courses of chemotherapy, the tumoral lesions were unchanged. This case underlines the role of Epstein-Barr virus infection in the development of unusual and clonal smooth-muscle tumors after organ transplantation. The evolution of these rare tumors is uncertain.

Statistical evaluation of diagnostic and prognostic features of CD30+ cutaneous lymphoproliferative disorders: a clinicopathologic study of 65 cases.

Several clinical and histopathologic features of 65 CD30+ cutaneous lymphoproliferations were evaluated for their diagnostic value between CD30+ primary versus secondary cutaneous lymphomas and for their prognostic significance. Primary cutaneous disease, spontaneous regression, and absence of extracutaneous spreading (but not age < or =60 years) were associated with a better prognosis. Epithelial membrane antigen, BNH9, CD15 or CBF.78 antigen were expressed in all types of cutaneous lymphoproliferations. However, epithelial membrane antigen immunoreactivity was more frequently expressed in CD30+ secondary cutaneous large-cell lymphoma. Among CD30+ primary cutaneous large-cell lymphoma, CD15 expression was only seen in localized skin lesions. P53 expression was not associated with spontaneous regression, extracutaneous spreading, or survival. Nested reverse transcriptase-polymerase chain reaction allowed the detection of NPM-ALK transcripts in 10 of 26 CD30+ primary and in 3 of 11 secondary cutaneous large-cell lymphomas. The ALK protein was detected in only 1 of 50 primary and in 4 of 15 secondary cutaneous CD30+ lymphoproliferations. In CD30+ primary cutaneous lymphoproliferation, NPM-ALK transcripts might be expressed by very rare normal or tumoral cells that are undetectable by immunohistochemistry. However, the expression of either NPM-ALK transcripts or ALK-protein was not correlated with prognosis or age in CD30+ cutaneous lymphoproliferations.

The Spectrum of Cutaneous Lymphomas in HIV infection: a study of 21 cases.

We studied 21 HIV-associated lymphomas with cutaneous presentation to determine whether they showed features of primary cutaneous lymphoma arising fortuitously or whether they represented the cutaneous involvement of AIDS systemic lymphoma. Besides rare mycosis fungoides (n = 3), which shared typical clinicopathologic lesions, nonepidermotropic large-cell lymphomas (n = 18) were predominant. They frequently presented as a solitary nodule or tumor. Seven of the eight large T-cell lymphomas had a CD30-positive (CD30+) phenotype but did not express ALK protein. Overexpression of p53 protein was observed in six cases. Although EBV-EBER transcripts were detected in two of them, LMP1 protein was absent. Except for their original prevalence, the features of these T-cell CD30+ cutaneous lymphomas were the same as in immunocompetent patients. The 10 B-cell cutaneous lymphoma were immunoblastic or centroblastic lymphomas, with a differential expression of BCL-6 and Syndecan. Four of them expressed CD30, EBER-EBV transcripts, and LMP1 and p53 proteins. This B-cell CD30+ EBV+ phenotype contrasts with cutaneous lymphoma in immunocompetent patients. Human herpesvirus 8 was not involved in lymphomagenesis since its sequences were detected in a single patient with Kaposi's sarcoma and Castleman's disease. These lymphomas occurred in severely immunocompromised patients with a low CD4 count. Death was due to immunodepression rather than to lymphoma spread, suggesting avoiding aggressive immunosuppressive treatment in such patients.

Identification of novel trkA variants with deletions in leucine-rich motifs of the extracellular domain.

The peripheral expression of trkA encoding for NGF receptor was investigated by RNase protection assay. A thymus-specific protected fragment was identified. Using 5' rapid amplification of cDNA ends, three different trkA fragments were characterized. The longer fragment corresponded to the classical trkA L3 transcripts while the two shorter fragments lacked sequences encoding for leucine-rich motifs of the extracellular domain of TrkA, similarly to the trkB L1 and L0 variants. RT-PCR analysis of adult rat tissues showed the expression of trkA L1 transcripts in the thymus, testis, lung and kidney but not in the central nervous system. Their combined expression with trkA L3 transcripts suggests that specific peripheral TrkA oligomers may modulate NGF binding and function in non-neuronal cells.