Intraperitoneal free cancer cells in non-gynaecological adenocarcinomas: a reproducibility study.

OBJECTIVE: In recent years, therapeutic approaches including cytoreductive surgery followed by intraperitoneal chemotherapy have proven effective in peritoneal carcinomatosis of colorectal origin. If cytology is to be used to include patients in aggressive treatment regimens, it is necessary to evaluate its performance, particularly in terms of specificity. The aim of this study was to assess interobserver agreement for the detection of intraperitoneal free cancer cells (IFCCs) in patients with non-gynaecological adenocarcinomas. METHODS: Over a 5-year period, 1223 patients were recruited in 19 French surgery departments. Peritoneal samples were examined in 14 dispersed pathology laboratories. Giemsa-stained slides were sent to a control reader blind to the previous diagnosis. Discordant cases, concordant positive results and a random selection of negative concordant cases were reviewed by a panel of seven cytopathologists. The 'final diagnosis' was that of the consensus meetings but took into account locally-processed slides. RESULTS: Gathering dubious cases with negative results, a 95.6% concordance was achieved between local readers and the control reader. IFCCs were ascertained by the panel in 85 cases (7.0%). Eight of 873 colorectal cancers cases viewed locally were falsely positive (0.9%). Radiotherapy and neoadjuvant therapy had no impact on the false-positive rate as assessed by final validation by the panel (P > 0.05). Samples initially considered as dubious were reclassified as negative by the panel in 24 of 25 cases (96.0%). CONCLUSIONS: The panel consensus allowed reclassification of most dubious/equivocal peritoneal cytology cases, whereas clearcut distinction between benign and malignant cases was correctly achieved in almost all cases.

Fine-needle aspiration biopsy with ultrasound guidance in patients with malignant melanoma and palpable lymph nodes.

BACKGROUND: Recurrence after treatment of stage I-II melanoma involves regional lymph nodes in about 50% of patients. A reliable method is needed to evaluate lymph node status (metastatic or not) in the case of palpable lymph nodes. OBJECTIVES: To evaluate the efficiency of fine-needle aspiration biopsy (FNAB) in examining clinically detected suspicious lymph node in patients followed up after surgical removal of stage I-II melanoma. PATIENTS AND METHODS: One hundred and twenty FNABs were performed in 67 patients with a suspicious node in an open study conducted in a French melanoma regional referral centre, Hôpital de l'Hôtel-Dieu. Cytodiagnosis was classified as positive, negative, inadequate or inconclusive. Sensitivity, specificity, positive and negative predictive values and positive and negative likelihood ratios were calculated after final histopathological evaluation. RESULTS: Fifty-eight of 120 FNABs were positive (48%), 50 of 120 (42%) were negative, four of 120 (3%) were inconclusive and eight of 120 (7%) were inadequate. Among the 108 FNABs in which a definitive diagnosis could be given, sensitivity was 98.2% [95% confidence interval (CI) 90.7-99.9] and specificity was 96.1% (95% CI 86.8-98.9). CONCLUSIONS: FNAB under ultrasound guidance is an efficient tool to discriminate better between cases in which surgical treatment of the lymph node basin should be performed and patients who should return for follow-up. Surgical treatment appears to be required in cases of positive FNAB or in inconclusive cases.

The mitochondrial-dependent pathway is chronically affected in testicular germ cell death in adult rats exposed in utero to anti-androgens.

In utero exposure to exogenous anti-androgenic compounds induces a wide range of abnormalities of the reproductive system, including hypospermatogenesis, cryptorchidism and hypospadias. By using rats exposed in utero to the anti-androgenic compound flutamide (0.4, 2 or 10 mg/kg per day), it has been shown that hypospermatogenesis in adult testes could be related to (i) a long-term apoptosis in germ cells but not in somatic Leydig and Sertoli cells as evidenced by the TUNEL approach and (ii) alterations in the mRNA and protein expression of pro- (Bax, Bak, Bid) and anti-apoptotic (Bcl-2, Bcl-w) members of the Bcl-2 family. Indeed, the number of apoptotic germ cells increased with the dose of flutamide administered and the apoptotic germ cells were mainly detected at androgen-dependent stages VII-VIII. Moreover, for the Bcl-2-related proteins that were expressed mainly in the germ cells, a decrease in the levels of anti-apoptotic peptides Bcl-w (60%, P=0.003) and Bcl-2 (90%, P=0.0001) was observed at 2 mg/kg per day flutamide and an increase in levels of the pro-apoptotic Bax (2.3-fold, P=0.0004) was detected at 10 mg/kg per day. In contrast, the levels of pro-apoptotic peptide Bak that was mainly expressed in somatic cells decreased (70%, P=0.0008) at 10 mg/kg per day. Such alterations in Bcl-2-related peptides occurred mainly at the protein level except for Bcl-2 (72%, P=0.0001) and Bak (43%, P=00002) transcripts. Together, these results showed that the apoptosis observed in adult germ cells from rats exposed in utero to flutamide may result from a long-term alteration in the balance between pro- and anti-apoptotic Bcl-2-related molecules in favour of pro-apoptotic proteins. These data further supported the concept of an androgen-dependent fetal programming that is in relation with an alteration of the expression of Bcl-2-related genes/proteins promoting apoptosis in testicular germ cells of adult rats with fetal androgen disruption.

Management of inguinal lymph node metastases in patients with carcinoma of the anal canal: experience in a series of 270 patients treated in Lyon and review of the literature.

BACKGROUND: The authors performed a specific analysis of the clinical significance of inguinal lymph nodes metastases in patients with anal canal carcinoma (ACC). METHODS: A retrospective analysis was conducted of 270 patients who were treated in Lyon between 1980 and 1996 with radiotherapy with curative intent for ACC: No elective irradiation of clinically normal inguinal areas was performed. Patients with metastatic inguinal lymph nodes were treated with inguinal dissection and postoperative irradiation with a dose of 50 grays over 5 weeks. Concomitant chemoradiation, usually with a regimen of fluorouracil and cisplatinum, was given to 159 patients. RESULTS: The median follow-up for the whole series was 72 months. Synchronous inguinal metastases were observed in 10% of patients (n = 27; the rate was 16% for patients with T3--T4 lesions), and the 5-year overall survival rate was 54.4%. Metachronous inguinal metastases were seen in 19 patients (7.8%), and the 5-year overall survival rate of these patients was 41.4%. An original finding was that, when the primary tumor clearly was located on a single lateral side of the anal canal, the inguinal lymphatic metastases was always homolateral to it (36 of 36 synchronous plus metachronous tumors). CONCLUSIONS: The data from this series of patients and a review of the literature are in favor of a selective approach in the management of inguinal lymph node involvement for patients with ACC, depending on the disease stage and the location of the primary tumors.

Fas and Fas ligand expression in cystic fibrosis airway epithelium.

BACKGROUND: Cystic fibrosis (CF) is a genetic disease caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene and defective expression of CFTR protein in epithelial cells. The main cause of mortality in CF is linked to chronic inflammatory and infectious airway processes. Recent studies have suggested perturbations in the apoptotic process in CF cell lines and enterocytes. A study was undertaken to investigate the expression of Fas and Fas ligand (FasL) in CF bronchial epithelium and CF tracheal cell lines. METHODS: Immunohistochemical staining for Fas (alkaline phosphatase anti-alkaline phosphatase) and FasL (immunoperoxidase) was performed in eight CF bronchial epithelial samples and four controls and immunohistochemical DNA fragmentation (TUNEL) was carried out in four CF patients and four controls. Immunofluorescence staining and flow cytometric analysis of Fas and FasL expression was performed in two human tracheal epithelial cell lines (HTEC) with normal and CF genotype. The dosage of serum soluble FasL was examined in 21 patients with CF and 14 healthy volunteers. RESULTS: FasL expression was markedly increased in patients with CF in both the ciliated and submucosal glandular bronchial epithelium compared with controls; Fas was similarly expressed in bronchial samples from controls and CF patients in both the ciliated epithelium and submucosal glands. High levels of DNA fragmentation were observed in CF but with some epithelial cell alterations. Serum concentrations of soluble FasL were frequently undetectable in patients with CF. In vitro, HTEC expressed Fas and FasL in both genotypes. A higher mean fluorescence intensity for FasL expression was noted in CF genotype HTEC with median (range) for six experiments of 74 (25-101) for CF cells and 42 (21-70) for non-CF cells. CONCLUSION: Fas/FasL interaction is probably implicated in the human CF airway apoptotic pathway. The mechanisms of induction of FasL expression and its role in inducing tissue damage or remodelling or in controlling local inflammatory cell apoptosis remain to be determined.

Variability of Ha-ras (codon 12) proto-oncogene mutations in diverse thyroid cancers.

Structural alterations to proto-oncogene sequences may be involved in the pathogenesis of human thyroid neoplasms. We studied 128 thyroid tumours (35 benign and 93 malignant) for ras gene point mutations in three different codons (12, 13 and 61) using a restriction fragment length polymorphism technique and direct sequencing of double-stranded DNA on polymerase chain-reaction-amplified tumour DNA. We found a high frequency of ras mutation for the Ha-ras codon 12 in follicular adenomas (7 of 35), particularly in atypical adenomas (5 of 17), in follicular carcinomas (6 of 19), with a high percentage for Hurthle cell carcinomas (6 of 11), and in papillary carcinomas (4 of 66). Point mutations for other ras genes in different codons studied were weak to absent. No mutation was found in undifferentiated carcinomas (n = 8). The predominant amino acid substitution both in the adenomas and in the differentiated tumours was glycine to valine (GGC to GTC) at position 12 of the Ha-ras gene. Our results obtained on a large series confirm the frequent occurrence of Ha-ras codon 12 gene mutations both in adenomas and in carcinomas. The frequency of ras mutations is linked to the geographical origin of the population studied and varies (0-85%) from one cancer type to another according to published data. Therefore, these mutations are merely an expression of cellular transformation.

[Thyroid nodules: assay of serum thyrotropin and cytopuncture versus scintigraphy as first-line tests. Prospective study with 150 cases]. / Nodules thyroïdiens: dosage d'hormone thyréotrope sérique et cytoponction versus scintigraphie comme examens de première intention. Etude prospective sur 150 observations.

OBJECTIVE: Fine-needle aspiration (FNA) is now considered as the first-line investigation for the diagnosis of thyroid nodules. We searched for a more accurate and cost-effective methodology as this technique fails to recognized hot nodules, frequent in certain countries. PATIENTS AND METHODS: A prospective study was conducted in 150 patients to compare two diagnostic procedures: scintigraphy first combined with FNA in case of cold nodules versus TSH measurement plus FNA when TSH measurement plus FNA when TSH was not depressed. The results were subjected to cost/benefit analysis. RESULTS: Cystic nodules were found in 28 cases (including 3 hyperfunctionning nodules, with 5 suspicious smears (1 carcinoma). FNA was non-diagnostic in 26 patients; 12 were operated on (1 carcinoma), 14 had further FNA (5 suspicious, 9 benign). Altogether 56 nodules were removed, for toxic adenoma (n = 5), for suspicious (n = 21) or malignant (n = 12) smear, or on personal (n = 18) demand; 16 carcinomas were found (2 medullary, 13 capillary, 1 follicular carcinomas). With scintigraphy first, the cost was 787 French francs (FF) per patient. With TSH measurement and FNA, the cost was 554 FF per patient. In both cases, the same number of carcinomas were removed, and all the hot nodules (11 including 5 toxic adenomas) were detected. CONCLUSION: Serum TSH measurement, with scintigraphy if TSH is low, and FNA in all the other cases, is accurate and more cost-effective than scintigraphy as a first-line investigation for the diagnosis of thyroid nodule.

Aerosol administration of a recombinant adenovirus expressing CFTR to cystic fibrosis patients: a phase I clinical trial.

Ad CFTR, a replication-deficient adenovirus expressing the human cystic fibrosis transmembrane conductance regulator (CFTR), was administered by aerosolization in a single escalating dose to three pairs (cohorts) of cystic fibrosis (CF) patients. Buffer only was administered to the nose and lungs 9-14 days before nasal instillation of virus followed the day after by aerosolization of Ad CFTR to the lung. Nasal doses (defined in terms of viral plaque forming units, pfu) were 10(5), 10(7), and 4 x 10(8), whereas aerosolized doses were 10(7), 10(8), 5.4 x 10(8) for each cohort, respectively. No acute toxic effects were observed in the first 4 weeks after virus treatment. Shedding of infectious Ad CFTR was never detected, whereas detection of vector DNA sequences and CFTR expression demonstrated DNA transfer to the nose and airways of patients. No significant deviations in immunological and inflammatory parameters were observed in serum and in bronchoalveolar lavage (BAL). Importantly, for all patients, the serum anti-adenovirus antibody levels did not change significantly from baseline and no antibodies against adenovirus were found in BAL.

[Evaluation of the role of cytology in the diagnosis of cancer of the lung. Comparison between cytology and pathological anatomy in 330 cases of proximal cancers]. / Evaluation du rôle de la cytologie dans le diagnostic des cancers du poumon. Comparaison entre la cytologie et l'anatomie pathologique sur 330 cas de cancers proximaux.

This retrospective study was performed to evaluate the interest of cytology in the diagnosis of pulmonary carcinomas. Bronchial samples were collected from 330 patients known to display a macroscopic lesion which was detected by bronchoscopy. Cytological analysis of the bronchial brushings and washings, removed at the first fibroscopy, allowed the diagnosis of malignancy in 92% of the cases analyzed whereas the biopsy confirmed the malignancy in 77% of the cases. In conclusion cytological studies gave information on malignity and classification in 90% of the cases. However histological classification only could guarantee the choice of the best treatment regimen.

Status and expression of the p16INK4 gene in human thyroid tumors and thyroid-tumor cell lines.

The p16INK4 tumor-suppressor gene (also known as CDKN2, CDK41 and MTS1) encodes a negative regulator of the cell cycle. This gene, located in 9p21, is mutated or homozygously deleted in a high percentage of tumor cell lines and specific types of primary tumors. We have examined the status of the p16INK4 gene in 31 thyroid tumors and 7 thyroid cell lines. No DNA abnormalities were found in primary tumors. Conversely, p16INK4 gene structural alterations, deletions and point mutations were found in 4 thyroid cell lines. The expression of the 2 different p16INK4 mRNAs, the p16alpha and p16beta transcripts, was determined by RNA-PCR experiments. All the primary thyroid tumors expressed the beta transcript, while the p16alpha was barely detectable. The thyroid cell lines always expressed the p16beta transcript, while the alpha transcript was absent or, whenever present, coded for a mutated form of the p16INK4 gene product. Taken together, our results suggest that loss of p16INK4 function is not directly involved in the process of thyroid-tumor development, but it probably gives cells in tissue culture a selective growth advantage.

Low frequency of p53 mutations in human thyroid tumours; p53 and Ras mutation in two out of fifty-six thyroid tumours.

OBJECTIVE: p53 is a well-known nuclear phosphoprotein encoded by a suppressor gene know to be mutated in various kinds of human tumours. A relationship between p53 gene mutation and tumour progression seems to be a common feature of several neoplasias. DESIGN: In order to investigate the role of p53 mutations in human thyroid tumours, DNA samples derived from fifty-six neoplastic tissues, ranging from benign adenomas to undifferentiated carcinomas, were examined for the presence of p53 gene mutations. METHODS: The analysis has been conducted using polymerase chain reaction (PCR) amplification of the exons 5-9 of the p53 gene followed by single strand conformation polymorphism (SSCP) and sequence analyses. RESULTS: One anaplastic carcinoma and one papillary carcinoma showed p53 gene mutations in exons 5 and 8, respectively. A cell line established from the papillary carcinoma showed the same mutation present in the original tumour. Both p53 mutations were heterozygous. The p53 positive samples were analysed for other genetic alterations frequently detected in human thyroid carcinomas (mutations of the RET, TRK, and ras oncogenes): both p53-mutated samples proved to be mutated at level of codon 13 of the c-Ki-ras gene. CONCLUSIONS: Our data confirm that p53 gene alterations are rare in well-differentiated thyroid tumours, that they are an important requirement for the establishment in culture of human thyroid carcinoma cell lines, and that they can be associated with other genetic alterations, namely ras mutations, in the malignant progression of thyroid tumours.

[Aerosol administration of a replication defective recombinant adenovirus expressing normal human cDNA-CFTR in the respiratory tractus in patients with cystic fibrosis]. / Administration par aérosol d'un adénovirus recombinant déficient pour la réplication contenant cADN-CFTR humain normal dans le tractus respiratoire de patients atteints de mucoviscidose.

At present it is conceivable to think that gene therapy represents a way to treat or even prevent the respiratory manifestations of cystic fibrosis. Consistent to such a concept, there is sufficient evidence that Ad-CFTR, a recombinant replication-deficient adenovirus expressing the human cystic fibrosis transmembrane conductance regulator cDNA, can vectorize the expression of a functional CFTR (cystic fibrosis transmembrane conductance regulator) to the nasal and airway epithelia. The clinical protocol was designed to assess the safety of single escalating doses of a replication defective adenovirus expressing the cystic fibrosis transmembrane conductance regulator gene (Ad-CFTR) when administered to the tracheobronchial portion of the airways and whether biological efficacy of CFTR delivery could be demonstrated. Six cystic fibrosis patients received nasal instillation and subsequent aerosol (Optineb, Air Liquide, Paris, France) administration of Ad-CFTR the following day. Doses (pfu) applied to the nose were 10(5) (patients SG and PB), 10(7) (patients FP and EP) and 4 x 10(8) (patients DS and FG), while aerosolised doses were 10(7) (patients SG and PB), 10(8) (patients FP and EP) and 5.4 x 10(8) (patients DS and FG), respectively. No acute toxic effects, no increase in the titer of anti-adenovirus antibodies and no spreading or shedding of Ad-CFTR were detected. In one patient Ad-CFTR DNA was found in the urine and blood two days after aerosolisation. Ad-CFTR DNA was detected in nasal and bronchial brush samples, in BAL, in saliva and tonsils 21, 8, 14 and 4 days post virus administration, respectively. Ad-CFTR mRNA (RT-PCR on bronchial cells) and CFTR protein (immunochemistry on nasal and bronchial cells) were detected up to 14 days following Ad-CFTR administration. These results show that the nebulisation of Ad-CFTR is a possible approach for treating the respiratory manifestation of cystic fibrosis.

Ha-ras oncogene (codon 12) mutation in thyroid carcinogenesis: analysis of 60 benign and malignant thyroid tumors.

Protooncogene Ha-ras codon 12 mutations are frequently observed in thyroid cancers. However, their role in the initiation and development of this pathology remains to be clarified. Here we present a preliminary study using 60 samples corresponding to different types of cancer. DNA amplification by PCR (polymerase chain reaction) followed by RFLP (restriction fragment length polymorphism) analysis enabled the detection of a point mutation in codon 12 of the Ha-ras oncogene in human thyroid adenomas and carcinomas. Our results confirm the high frequency of codon 12 Ha-ras oncogene mutation in thyroid tumors: adenomas 33%, with a particularly high rate for atypical adenomas 71%, follicular carcinomas 33%, and papillary carcinomas 19% (n = 18, 7, 12, 26, respectively). No mutation was detected in undifferentiated carcinomas (n = 4). The Ha-ras codon 12 gene point mutation can exist at all stages of development of both benign and malignant thyroid tumors. It may be a necessary part of the thyroid tumorigenesis process, but it is not the only carcinogenic factor. Additionally, the association with other molecular anomalies should be sought depending on the thyroid cancer type.

Production of tgf-Beta and hgf receptor by a differentiated papillary thyroid-carcinoma cell-line (B-cpap) - implication in malignancy.

The B-CPAP cell line was obtained from a human differentiated papillary thyroid carcinoma. Previous studies showed that the cells present thyroid characteristics such as thyroglobulin production, phenotypic alterations such as synthesis of human chorionic gonadotropin hormone (HCG), expression of neuron specific enolase (NSE) and protein S100, and also somatic mutations of p53 and K-rns oncogenes. The present data further characterize this cell line and show an overexpression of transforming growth factor (TGF beta 1) and c-met gene product i.e. the receptor for human growth factor (HGF). The relation between the phenotypic and somatic alterations in the process of malignancy are discussed.

Description of a human papillary thyroid carcinoma cell line. Morphologic study and expression of tumoral markers.

BACKGROUND: The establishment of cell lines from thyroid carcinomas can provide an in vitro model of oncogenesis. B-CPAP is a new cell line that has been obtained from a differentiated papillary thyroid carcinoma. The data presented give a broader characterization and expression of tumoral markers of this cell line and identify the differentiated functions that are preserved. METHODS: An ultrastructural study was performed to confirm the thyroid nature of the new cell line. The cellular markers (thyroglobulin, S100, neuron-specific enolase [NSE]) and the oncogenes (mutated p53, H-ras, c-myc, PTC, trk) were studied by immunohistochemistry, Southern blot, or in situ hybridization. RESULTS: The cells were of a differentiated ultrastructural thyroid type. All of the cells proved immunoreactive with antibodies specific to thyroglobulin, S100 proteins, NSE, and mutant p53 protein. Mutations of H-ras, PTC, and trk were not observed. The c-myc gene was not amplified. CONCLUSIONS: The cell line described in these data provides a suitable model for the study of thyroid carcinogenesis, given that the cells present thyroid characteristics, and metabolic disorders not previously found in such cell lines. In addition, the coexpression of S100 proteins and mutant p53 proteins in the cells should permit the study of the interaction between these two proteins.

Allergenic exposure, IgE-mediated sensitization, and related symptoms in lawn cutters.

AIMS: The aims of the study conducted on lawn cutters were: (1) to evaluate exposure to pollens and molds; and (2) to assess the prevalence rate of IgE sensitization and symptoms in relation to exposure to pollens and molds. METHODS: Environmental assessment was done with the use of personal samplers on eight workers. Our population consisted of 181 municipal park workers, including 128 lawn cutters and 67 control subjects (blue-collar workers in the hospital). A questionnaire was administered, as well as skin prick tests with seven common inhalants including pollens and eight grass molds. The main outcome variables were grass or mold sensitization (at least one of eight molds) and work-related rhinitis, conjunctivitis, and rhinoconjunctivitis. Atopy and exposure to park-related allergens, as well as sensitization to grass pollens, were considered as explanatory factors. Smoking was taken into consideration as a covariant. Both presence and duration of occupational exposure to park-related allergens were considered as parameters of exposure. Duration of exposure (months x years of exposure as lawn cutters) was used as a continuous or as a categorical variable. RESULTS: Environmental monitoring showed that the concentration of pollens and molds decreased in magnitude from samples collected close to lawn cutters faces, short distance away in parks, and in the general environment. There was no difference in the prevalence rates for atopy between lawn cutters (32%) and control subjects (37%). Sensitization rates to grass pollen were also similar in lawn cutters (18%) and in control subjects (22%). However, there was a tendency for prevalence rates of sensitization to molds to be greater among lawn cutters (12% to Alternaria) compared with control subjects (5%). In the logistic model atopy was significantly related to grass sensitization (odds ratio [OR] = 7.2), mold sensitization (OR = 9.3), and sensitization to Alternaria (OR = 5.8). Grass sensitization was a significant risk factor for park-related rhinitis (OR = 5.8), conjunctivitis (OR = 5.0), and rhinoconjunctivitis (OR = 9.4). Exposure for 12 years or more was associated with rhinoconjunctivitis with an OR of 4.1 (95% confidence interval, 1.0-16.7). Smoking was not significantly related to any outcome. CONCLUSION: We conclude that among lawn cutters exposure to pollens and molds is higher than in the general population, atopy is the main determinant of sensitization to these aeroallergens, and sensitization and, to a much lesser extent, exposure to grass are determinants of symptoms.

Molecular characterization of RET/PTC3; a novel rearranged version of the RETproto-oncogene in a human thyroid papillary carcinoma.

The RET proto-oncogene encodes a transmembrane receptor of the tyrosine kinase family and has frequently been found activated in human thyroid carcinomas of the papillary subtype. In most cases the activation consisted of the fusion of its tyrosine-kinase domain with the 5'-terminal region of a gene designated H4 or D10S170. We have named the resulting H4/RET chimeric oncogene RET/PTC. Another activated form of the RET oncogene has subsequently been found in a thyroid carcinoma and is now referred to as RET/PTC2. Here we report the identification and cloning of a novel rearranged version of the RET oncogene in a human thyroid papillary carcinoma. In this case the tyrosine-kinase domain of RET was fused to a sequence 790 bp long belonging to a new gene that we have named RFG (RET Fused Gene). This novel chimeric oncogene has been designated RET/PTC3. In order to have more insights into the function of RFG we have completely cloned and sequenced its cDNA. RFG predicted amino-acid sequence does not have any significant homology to any already known genes and is ubiquitously expressed in human and mouse tissues. Finally we provide evidence indicating that the rearrangement leading to the generation of RET/PTC3 occurred in vivo in the original tumor DNA.

The ret protooncogene is expressed in predominantly epithelial human thymomas.

Thymomas are thymic tumors composed of epithelial cells with various number of lymphocytes. On the basis of lymphocytes number, they can be histologically classified into predominantly lymphocytic, predominantly epithelial and mixed lympho-epithelial. These tumors are rare and their prognosis is not well known yet. In this study we demonstrate by in situ hybridization the presence of RET transcripts in the medullary part of normal murine thymus and in epithelial thymomas. Conversely RET expression was not detected in the cortical part of the thymus and in thymomas with the predominance of the lymphocytic component, suggesting that its expression could be a specific marker of the predominantly epithelial histotype.

The ret protooncogene is expressed in normal human parafollicular thyroid-cells.

The RET proto-oncogene has been demonstrated to be expressed in medullary thyroid carcinomas and pheochromocytomas, and was mutated in patients with the multiple endocrine neoplasia type 2A (MEN 2A). The results presented herein show its expression in normal human thyroid parafollicular C cells. Since RET is predicted to encode a receptor for a still unknown ligand, these data confirm its involvement in the regulation and growth of these cells.

Involvement of RET oncogene in human tumours: specificity of RET activation to thyroid tumours.

Non-thyroid neoplasia were analysed by Southern blot of genomic DNA and DNA prepared by reverse transcription and amplification by polymerase chain reaction (RT/PCR) for the activation of the RET oncogene. It is known that the rearrangement of RET occurs in about 10%-20% of human thyroid papillary carcinomas. None of 528 non-thyroid tumours showed rearrangement of the RET proto-oncogene, whereas three out of 30 thyroid papillary carcinomas were positive for RET activation. Therefore the activation of RET seems to be a somatic cell mutation specific to human thyroid carcinomas.