Diagnostic and prognostic value of 18-fluorodeoxyglucose positron emission tomography in adrenocortical carcinoma: a prospective comparison with computed tomography.

OBJECTIVE: Patients with adrenocortical cancer are submitted to multiple imaging procedures for diagnosis of recurrence and staging. The aim of this prospective study was to evaluate the diagnostic and prognostic values of fluorodeoxyglucose (FDG) using a combined positron emission tomography and computed tomography (PET/CT) modality, compared with thoracoabdominopelvic computed tomography (TAP-CT). METHODS: Twenty-eight consecutive patients with adrenocortical cancer referred from November 2003 to December 2004 to the Institut Gustave Roussy were included. Mean time between PET/CT and TAP-CT was 16 d. Independent readers analyzed images of each modality. The gold standard was progression on follow-up TAP-CT or pathology. RESULTS: A total of 269 lesions in 57 organs were depicted in 22 patients. The sensitivities for the detection of distinct lesions and the diagnosis of metastatic organs were 90 and 93% for PET/CT and 88 and 82% for TAP-CT, respectively. Twelve percent of the lesions were seen on PET/CT only and 10% on TAP-CT only. Eighteen percent of the metastatic organs were diagnosed with PET/CT only and 7% with TAP-CT only. Thirty-eight percent of the local relapses were seen only with PET/CT. PET/CT depicted three false-positive lesions. Treatment modalities were modified by PET/CT findings in five cases among which one was falsely positive. Tumor size and mitotic rate were significantly associated with FDG uptake. The intensity of FDG uptake (maximum standardized uptake value > 10) and the volume of FDG uptake (>150 ml) were significant prognostic factors for survival. CONCLUSIONS: We show that FDG-PET/CT is complementary to TAP-CT and of special interest in the diagnosis of local relapses.

Long-term outcome of 444 patients with distant metastases from papillary and follicular thyroid carcinoma: benefits and limits of radioiodine therapy.

AIM: The goal of this study was to estimate the cumulative activity of (131)I to be administered to patients with distant metastases from thyroid carcinoma. METHODS: A total of 444 patients were treated from 1953-1994 for distant metastases from papillary and follicular thyroid carcinoma: 223 had lung metastases only, 115 had bone metastases only, 82 had both lung and bone metastases, and 24 had metastases at other sites. Treatment consisted of the administration of 3.7 GBq (100 mCi) (131)I after withdrawal of thyroid hormone treatment, every 3-9 months during the first 2 yr and then once a year until the disappearance of any metastatic uptake. Thyroxine treatment was given at suppressive doses between (131)I treatment courses. RESULTS: Negative imaging studies (negative total body (131)I scans and conventional radiographs) were attained in 43% of the 295 patients with (131)I uptake; more frequently in those who were younger, had well-differentiated tumors, and had a limited extent of disease. Most negative studies (96%) were obtained after the administration of 3.7-22 GBq (100-600 mCi). Almost half of negative studies were obtained more than 5 yr after the initiation of the treatment of metastases. Among patients who achieved a negative study, only 7% experienced a subsequent tumor recurrence. Overall survival at 10 yr after initiation of (131)I treatment was 92% in patients who achieved a negative study and 19% in those who did not. CONCLUSION: (131)I treatment is highly effective in younger patients with (131)I uptake and with small metastases. They should be treated until the disappearance of any uptake or until a cumulative activity of 22 GBq has been administered. In the other patients, other treatment modalities should be used when tumor progression has been documented.

Ectopic hematopoiesis in peritoneal tumor nodules induced by the myeloproliferative sarcoma virus in DBA/2 mice.

Tumor nodules composed of fibroblasts, large undifferentiated cells, granulocytes, and small lymphocytes develop in the spleens of adult DBA/2 mice infected with the myeloproliferative sarcoma virus (MPSV). They spread thereafter in the organism, and at the terminal stage of the disease they are especially numerous on the peritoneal membrane. The present study, performed on those tumor nodules to avoid contamination by exogenous hematopoietic cells, demonstrated that they were sites of granulopoiesis, which may have occurred via the local differentiation of granulomacrophage precursor cells (GM-CFC) and perhaps also from pluripotent hematopoietic stem cells, since these two populations were present in the tumor nodules (25 +/- 11 and 13 +/- 10, respectively, per 5-10(5) cells). Almost all (88%) those GM-CFC were able to clone in vitro without added colony-stimulating factor. A comparative study with the Moloney murine sarcoma virus-induced tumor indicated that the local production of hematopoiesis-stimulating factors was not sufficient to allow such ectopic granulopoiesis. These results imply the presence of a specific hematopoietic microenvironment in the MPSV-induced tumor nodules.

Apoptosis induced in Burkitt's lymphoma cells via Gb3/CD77, a glycolipid antigen.

Gb3/CD77 is a glycolipid antigen, specifically expressed on two different B-cell populations, Burkitt's lymphoma and a subset of tonsillar B-lymphocytes located in germinal centers, which could be the normal counterpart of Burkitt cells. Both Gb3/CD77(+) populations have recently been shown to enter programmed cell death (apoptosis) readily. Here we show that verotoxin, also called Shiga-like toxin, which is known to bind to the carbohydrate moiety of Gb3/CD77, induces cell death in Gb3/CD77(+) Burkitt's lymphoma cells, not only by inhibiting protein synthesis as classically described but also through an additional mechanism, namely apoptosis. Furthermore a recombinant B-subunit of verotoxin, which carries only the binding property of the holotoxin, also induces apoptosis in Gb3/CD77(+) cells. Gb3/CD77 could thus represent the first example of a glycolipid antigen able to transduce a signal leading to apoptosis.

Identification of genes overexpressed in tumors through preferential expression screening in trophoblasts.

Early trophoblastic cells share several features with neoplastic cells. Based on that observation, we attempted to identify genes overexpressed in tumors by analyzing genes preferentially expressed in trophoblasts. A subtracted library enriched in complementary DNA from early cytotrophoblasts was constructed, and the expression level of selected recombinants was analyzed on a large panel of normal and tumor tissues. The library was prepared using a polymerase chain reaction-based complementary DNA subtraction method with 6-week amenorrhea cytotrophoblast endoplasmic reticulum-bound RNA as target, and a mixture of complementary DNA prepared from terminal placenta and activated T-lymphocytes as driver. Two rounds of screening were performed to isolate clones preferentially expressed in early placenta. From a total number of recombinant clones estimated at 32,000 in the subtracted library, 594 inserts were analyzed by Southern blot and 21 sequences were isolated as corresponding to genes highly expressed in early placenta. Eleven encoded known molecules, such as carcinoembryonic antigen, human chorionic gonadotropin, and mitochondrial rRNAs. Ten sequences represented novel genes. Northern blot analysis confirmed that most of these genes were preferentially expressed in early trophoblast in comparison to terminal placenta. Three clones that gave detectable hybridization signals on total RNA were extensively studied and were found to be overexpressed in various tumors. Two of these clones, designated B9 and E4, were later identified as corresponding to genes coding for the putative ribosomal protein S18 and the bifunctional enzyme ADE2H1 involved in purine biosynthesis, respectively. Expression of the third clone, E9, was increased up to 10-fold in breast cancer tissues in comparison with normal counterparts. Present results confirm that many genes expressed in the trophoblast are overexpressed in malignant cells. This approach could provide a general targeted method for the identification of genes overexpressed in various neoplastic cell types.

Positive anticalcitonin immunoscintigraphy in patients with medullary thyroid carcinoma.

A cocktail of three monoclonal F(ab')2 fragments against three distinct epitopes of calcitonin or PDN 21 was labelled with either 111In or 131I. These F(ab')2 fragments, a control 125I-F(ab')2 fragment and 99mTc-pertechnetate were injected into four patients suffering from medullary thyroid carcinoma. Scintigraphy data were processed by energy factor analysis for an optimal separation of images corresponding to each isotope. The best tumor detection was obtained 1-3 days after injection of the 111In-F(ab')2 cocktail which clearly labeled the thyroid tumors in the four patients (smallest tumor detected, 0.6 cm) as well as lymph node and bone metastases. In the liver, positive detection was only successful with the 131I-labeled cocktail. These results were confirmed by counting rates of resected specimens which provided average specificity indices ranging from 3.3 to 13.1. Anticalcitonin antibodies could be particularly useful for immunoscintigraphy detection of residual or recurrent medullary thyroid carcinoma in patients with elevated calcitonin serum level.

gsp mutations in human thyroid tumours.

The presence of gsp mutations at codons 201 and 227 in the gene coding for the alpha subunit of the GTP-binding Gs protein which stimulates adenylyl cyclase (AC) has been investigated in 31 samples of differentiated thyroid tumours, which had been previously characterized with respect to their adenylyl cyclase activity (ACA) before and after stimulation by thyroid-stimulating hormone (TSH). Polymerase chain reaction (PCR) amplification of DNA extracted from these tumours, followed by high stringency oligonucleotide probing, enabled the detection of mutations in three samples originating from tumours with high constitutive ACA, which was not significantly further stimulated by TSH. Two mutations were at codon 227 and replaced Gln227 by His or Lys, and one was at codon 201, with the substitution of Arg201 by Ser. Because thyrocytes belong to the subset of differentiated cells which are programmed to proliferate in response to elevated cAMP levels, the gsp mutations observed in some differentiated thyroid carcinomas probably contributed to their tumorigenic phenotype.

Detection of activated ras oncogenes in human thyroid carcinomas.

Focus formation following DNA transfection of mouse 3T3-Vill cells was used to search for the presence of activated oncogenes in human thyroid tumors. Oncogenes belonging to the ras family were detected in four out of six thyroid carcinomas (Ki-ras in one anaplastic tumor and one follicular moderately differentiated tumor and Ha-ras and N-ras in two papillary tumors). Normal thyroid tissue samples obtained from two patients, one with an anaplastic tumor and one with a benign adenoma, and samples from 4 benign adenomas and from one toxic goiter of a patient with Graves' disease gave negative results. In one case, restriction enzyme analysis demonstrated the presence of a mutation in codon 12 of the activated Ha-ras oncogene. Our data show that all three ras proto-oncogenes can become activated in malignant thyroid tumors.

High prevalence of activating ret proto-oncogene rearrangements, in thyroid tumors from patients who had received external radiation.

A high frequency (about 60%) of ret rearrangements in papillary thyroid carcinomas of children exposed to radioactive fallout in Belarus after the Chernobyl accident, has been reported by three recent studies (Fugazzola et al., 1995; Ito et al., 1994; Klugbauer et al., 1995). These studies suggested that the radiation exposure may be a direct inducer of activating rearrangements in the ret gene. In order to confirm the postulated link between irradiation and the role of the ret proto-oncogene in thyroid tumorigenesis, we analysed for the presence of ret activating rearrangements using RT-PCR, XL-PCR, Southern blot and direct sequencing techniques, 39 human thyroid tumors (19 papillary carcinomas and 20 follicular adenomas), from patients who had received external radiation for benign or malignant conditions. As controls, we studied 39 'spontaneous' tumors (20 papillary carcinomas and 19 follicular adenomas). Our data concerning the radiation-associated tumors, showed that: (1) the overall frequency of ret rearrangements was 84% in papillary carcinomas (16/19) and 45% (9/20) in follicular adenomas; (2) in contrast with the results obtained in the Chernobyl tumors, the most frequently observed chimeric gene was RET/PTC1 instead of the RET/PTC3 and (3) all the tumors were negative for RET/PTC2. In the 'spontaneous' tumors, only the papillary carcinomas presented a ret rearrangement (15%:3/20): 1 RET/PTC1, 1 RET/ PTC3 and 1 uncharacterized. In conclusion, our results confirm the crucial role played by the ret proto-oncogene activating rearrangements in the development of radiation-associated thyroid tumors appearing after therapeutic or accidental ionizing irradiation, and show, for the first time, the presence of RET/PTC genes in follicular adenomas appeared after external irradiation.

Activating mutations of the TSH receptor in differentiated thyroid carcinomas.

A series of 14 thyroid carcinomas, characterized for their basal adenyl cyclase activity (ACA), was examined for the presence of activating point mutations in the TSH receptor (TSHR) gene. Sequencing of the carboxyl-part of this gene revealed the presence of a somatic and heterozygotic point mutation in codon 623 in three out of six tumors showing a constitutively enhanced ACA and a poor response to TSH stimulation. The mutation determines the substitution of a serine for an alanine in the third intracellular loop of the receptor, in a region critical for signal transduction. One tumor bearing a TSHR mutation presented also a N-ras point mutation. Both mutations were detected also in a lung metastasis of this tumor. Our data represent the first report of alterations in the TSHR gene in thyroid malign neoplasia. TSHR mutations may indeed participate, as well as the G alpha s protein (gsp oncogene), in the oncogenesis of some differentiated thyroid carcinomas presenting increased basal levels of cAMP and a poor response to TSH.

Thyroid pathologies in transgenic mice expressing a human activated Ras gene driven by a thyroglobulin promoter.

Four transgenic mice carrying the human activated c-Ha-Ras gene, the expression of which was driven into the thyroid gland by a bovine thyroglobulin promoter, have been produced. The M1 and M2 mice developed papillary thyroid carcinomas and the M2 mouse also developed a lung carcinoma, however none of them transmitted the transgene. Both the M3 and the M4 mice gave rise to transgenic lines. M3 progeny mice develop a goitre with morphological aspects of hyperplasia as well as a thymus hyperplasia. M4 developed a papillary thyroid carcinoma and a lung carcinoma. Lung tumors but not thyroid tumors were observed in M4 adult transgenic progeny. In this M4 line, thyroid dysgenesis leading to growth retardation and premature death was observed upon serial backcross that enhanced the DBA/2J genetic background. The development of thyroid tumors in M1, M2, M4 transgenic mice demonstrates the oncogenic potential of activated Ras gene in the thyroid gland. The M4 line raises interesting questions relative to the interference between the Ras-mediated signal transduction pathway and thyroid morphogenesis.

Pattern of ras and gsp oncogene mutations in radiation-associated human thyroid tumors.

The preferential activation of the Ki-ras oncogene in follicular radiation-associated human thyroid carcinomas, has been suggested by Wright et al. (1991). However, only 12 thyroid tumors were analysed in this study. In order to confirm if radiation favours, in human thyroid tumorigenesis, the appearance of a particular molecular lesion, we studied 33 benign and malignant human radiation-associated thyroid tumors. We used polymerase chain reaction (PCR) amplification and allele-specific hybridization with mutant-specific probes for the three ras genes and the gsp oncogene. Compared to 85 'spontaneous' human thyroid tumors, the radiation-associated cases: (1) show a similar overall frequency of ras and gsp mutations (about 30% and 6% respectively); (2) present a similar frequency of mutation of the three ras genes without any predominance in adenomas and papillary carcinomas and (3) all Ki-ras mutations were found in papillary carcinomas (4/15). ras and gsp genes were never found mutated simultaneously, suggesting an alternative role for both oncogenes in the thyroid tumorigenic radiation-associated process.

Presence of mutations in all three ras genes in human thyroid tumors.

Polymerase chain reaction (PCR) amplification followed by oligonucleotide probing was used to investigate the presence of ras genes mutations in human thyroid adenomas and carcinomas. The results confirm the frequent occurrence of mutations in all three ras genes in both adenomas and carcinomas, in agreement with the hypothesis that the ras mutations may constitute early steps in thyroid tumorigenesis. No evident correlation between the frequency of ras mutations, the identity of the mutated ras gene, the position affected in the ras gene or the type of mutation and the pathological features is apparent. However, definitive conclusion on this point is precluded because of the small number of tumors examined at the present time.

Tumor-infiltrating CD3- NK cells are more effective than CD3+ T cells in killing autologous melanoma cells.

We have studied the phenotype and functional activity of tumor-infiltrating lymphocytes (TIL) derived from eight human melanomas cultured for up to 60 d in the presence of recombinant IL-2. In the early period of the cultures, TIL were predominantly T cells of CD8+ phenotype and contained 10-30% of CD3- cells. Four of the five early TIL cultures tested in a cytotoxicity assay displayed a degree of MHC-unrestricted lysis on a series of autologous and allogenic melanoma cell lines as well as the K562 natural killer-sensitive target. With longer periods of time in culture, all TIL lines showed a decrease in lytic activity that was associated with the loss of CD3- cells. Thus, most of the killing of short-term TIL cultures appeared to be mediated by CD3- natural killer cells, whereas CD3+ T cells were found to be weak anti-tumor effectors. Even though the CD3+ T cells were not cytotoxic on K562 targets, their lytic activity (even weak) against melanoma cells appeared to be non-MHC restricted, and was blocked by anti-CD3 antibodies. In addition, cytotoxicity of the CD3+ TIL cultures was compared to that of a CD3-/NKH1+ cell line purified from peripheral blood. It was found that natural killer cells were much more potent than CD3+ TIL on the melanoma cell lines tested.

Octreotide scintigraphy in patients with differentiated thyroid carcinoma: contribution for patients with negative radioiodine scan.

Somatostatin receptor scintigraphy (SRS) was evaluated in 25 differentiated thyroid carcinoma (DTC) patients. All DTC patients had elevated thyroglobulin levels. A total body scan (TBS) was performed 4 and 24 h after injection of indium-111-DTPA-Phe-octreotide. Group 1 included 16 patients with negative 131I TBS; group 2 had 9 patients with positive 131I TBS. SRS results were compared to the results of conventional imaging methods in group 1 and to 131I TBS in group 2. 131I TBS was performed after administration of a therapeutic dose of 131I in all patients except one. SRS was positive in 20 of 25 (80%) patients. In group 1, SRS was positive in 12 of 16 patients; in the 3 patients with no previously known tumor site, SRS visualized one abnormal neck focus of uptake in two. In the other 13 patients, SRS disclosed unknown mediastinal foci in 2, but visualized less organ involvements and a smaller number of tumor sites than conventional imaging methods. In group 2, SRS was positive in 8 of 9 patients and visualized an identical (7 patients) or a smaller number (1 patient) of involved organs than 131I TBS; in 2 patients, SRS allowed the discovery of 1 abdominal and 1 bone tumor site. We suggest than SRS should guide imaging modalities in DTC patients with negative 131I TBS and be an alternative to 131I TBS in DTC patients unable to withdraw T4 treatment.

Expression of pendrin and the Pendred syndrome (PDS) gene in human thyroid tissues.

The gene recently cloned that is responsible for the Pendred syndrome (PDS), an autosomal recessive disease characterized by goiter and congenital sensorineural deafness, is mainly expressed in the thyroid gland. Its product, designated pendrin, was shown to transport chloride and iodide. To investigate whether the PDS gene is altered during thyroid tumorigenesis, PDS gene expression and pendrin expression were studied using real-time kinetic quantitative PCR and antipeptide antibodies, respectively, in normal, benign, and malignant human thyroid tissues. The results were then compared to those observed for sodium/iodide symporter (NIS) expression. In normal tissue, pendrin is localized at the apical pole of thyrocytes, and this in contrast to the basolateral location of NIS. Immunostaining for pendrin was heterogeneous both inside and among follicles. In hyperfunctioning adenomas, the PDS messenger ribonucleic acid level was in the normal range, although immunohistochemical analysis showed strong staining in the majority of follicular cells. In hypofunctioning adenomas, mean PDS gene expression was similar to that detected in normal thyroid tissues, but pendrin immunostaining was highly variable. In thyroid carcinomas, PDS gene expression was dramatically decreased, and pendrin immunostaining was low and was positive only in rare tumor cells. This expression profile was similar to that observed for the NIS gene and its protein product. In conclusion, our study demonstrates that pendrin is located at the apical membrane of thyrocytes and that PDS gene expression is decreased in thyroid carcinomas.

Expression of the Na+/I- symporter gene in human thyroid tumors: a comparison study with other thyroid-specific genes.

The expression of 4 thyroid tissue-specific genes [Na+/I- symporter (NIS), thyroid peroxidase (TPO), thyroglobulin (Tg), TSH receptor (TSH-R)] as well as of the glucose transporter type 1 (Glut1) gene was analyzed in 90 human thyroid tissues Messenger ribonucleic acids were extracted from 43 thyroid carcinomas (38 papillary and 5 follicular), 24 cold adenomas, 5 Graves' thyroid tissues, 8 toxic adenomas, and 5 hyperplastic thyroid tissues; 5 normal thyroid tissues were used as reference. A kinetic quantitative PCR method, based on the fluorescent TaqMan methodology and real-time measurement of fluorescence, was used. NIS expression was decreased in 40 of 43 thyroid carcinomas (10- to 1200-fold) and in 20 of 24 cold adenomas (2- to 700-fold); it was increased in toxic adenomas and Graves' thyroid tissues (up to 140-fold). TPO expression was decreased in thyroid carcinomas, but was normal in cold adenomas; it was increased in toxic adenomas and Graves' thyroid tissues Tg expression was decreased in thyroid carcinomas, but was normal in the other tissues. TSH-R expression was normal in most tissues studied and was decreased in only some thyroid carcinomas. In thyroid cancer tissues, a positive relationship was found between the individual levels of expression of NIS, TPO, Tg and TSH-R. No relationship was found with the age of the patient. Higher tumor stages (stages >I vs stage I) were associated with lower expression of NIS (P = 0.03) and TPO (P < 0.01). Expression of the Glut1 gene was increased in 1 of 24 adenomas and in 8 of 43 thyroid carcinomas. In 6 thyroid carcinoma patients, 131I uptake was studied in vivo; NIS expression was low in all samples; 3 patients with normal Glut-1 gene expression had 131I uptake in metastases, whereas the other 3 patients with increased Glut-1 gene expression had no detectable 131I uptake. In conclusion, this study shows 1) a reduced expression of NIS gene in most hypofunctioning benign and malignant thyroid tumors; 2) a differential regulation of the expression of thyroid-specific genes; 3) an increased expression of Glut-1 gene in some malignant tumors that may suggest a role for glucose derivative tracers to detect in vivo thyroid cancer metastases by positron emission tomography scanning.

Na+/I- symporter distribution in human thyroid tissues: an immunohistochemical study.

Antipeptide antibodies raised against the carboxyl-terminal region of the human sodium/iodide (Na+/I-) symporter (hNIS) were used to investigate by immunohistochemistry the presence and distribution of the hNIS protein in normal thyroid tissues, in some pathological nonneoplastic thyroid tissues, and in different histotypes of thyroid neoplasms. In normal thyroid tissue, staining of hNIS protein was heterogeneous and limited to a minority of follicular cells that were in close contact with capillary vessels. In positive cells, immunostaining was limited to the basolateral membrane. In contrast, in Graves' disease the majority of follicular cells expressed the hNIS protein. In autoimmune thyroiditis, the number of hNIS-positive cells, was similar to that found in normal tissue. These positive cells were found essentially close to lymphocytic infiltrates. This observation supports the concept of hNIS as an autoantigen. In diffuse nodular hyperplasia, hNIS staining was heterogeneous, but the number of hNIS-positive cells exceeded that found in normal tissue. In well differentiated follicular or papillary carcinoma, the number of hNIS-positive cells was significantly lower than in normal tissue. In poorly differentiated follicular carcinoma, the number ofhNIS-positive cells was less than that found in well differentiated carcinoma, or there were no positive cells. Interestingly, in all of these thyroid tissues, the number of follicular cells exhibiting TSH receptor (TSHR) immunoreactivity was greater than the number ofhNIS-positive cells. As hNIS expression appears to be related to TSHR stimulation, the decreased number of TSHR-positive cells in cancers may contribute to the reduced capacity of neoplastic cells to concentrate iodide. In one patient with a follicular cancer with an absence of hNIS immunostaining, the total body 131I scan showed no uptake in metastatic tissue. In three cancers with positive hNIS cells, the 131I scan showed uptake in lymph node metastases. This suggests that immunodetection of hNIS could predict radioiodine uptake in thyroid cancers.

Combination of radioiodine (131I) and probe-guided surgery for persistent or recurrent thyroid carcinoma.

To improve the completeness of surgical excision of persistent or recurrent differentiated thyroid carcinoma, the following protocol was used for the treatment of 54 patients with functioning lymph node metastases: administration of 3.7 gigabecquerels (100 mCi) 131I; total body scintigraphy (TBS) on day 4; surgery on day 5, using an intraoperative probe (Gammed 2, Eurorad); and postoperative TBS with the remaining 131I activity on day 7. The 54 patients (35 women and 19 men presenting 47 papillary carcinomas, 2 well differentiated follicular carcinomas, and 5 poorly differentiated follicular carcinomas) had already undergone surgery for differentiated thyroid carcinoma: total thyroidectomy (51 patients) or lobectomy with isthmusectomy (3 patients), with lymph node dissection in 33. One to 7 131I treatments were performed before inclusion. Preoperative 131I-TBS with a high dose of 131I allowed accurate localization of previously suspected neoplastic foci and detection of yet unknown foci in 56%; it was the most sensitive tool for localizing neoplastic foci. The use of an intraoperative probe was considered decisive in 20 patients, as neoplastic foci were found inside sclerosis due to previous surgery (n = 9), at unusual sites behind vessels or in the mediastinum (n = 10), or both (n = 1). In 26 patients, it facilitated the preoperative detection of foci with 131I uptake already depicted at preoperative 131I-TBS. In all 46 patients, the completeness of excision was demonstrated by both the probe and the postoperative 131I-TBS and was confirmed during follow-up. Of note, lymph node metastases undetected by 131I-TBS or by the probe were found in 14 patients at histological examination. This clearly shows that en block dissection is the only recommended procedure. In four patients, no neoplastic foci were found and in four patients, uptake was either due to the thymus (in two) or to the salivary glands (in two).

Expression of Na+/I- symporter and Pendred syndrome genes in trophoblast cells.

Placental iodide transport is critical for the fetal thyroid function, but the molecular mechanisms of this transport are not understood. The expression of two recently identified iodide transporters, namely the sodium/iodide symporter (NIS) and pendrin, the product of the gene responsible for the Pendred syndrome (PDS), was studied using real-time kinetic quantitative PCR and immunohistochemistry 1) in placental tissues collected at different gestational ages and 2) in primary cultures of villous cytotrophoblast cells (VCT) that differentiate and fuse over 2-3 days in vitro to form villous syncytiotrophoblast (VSCT) cells. Both NIS and PDS genes are expressed in placenta, albeit at low levels compared with those in thyroid tissue. NIS gene expression in placental samples from first trimester and term pregnancies was similar. In contrast, the expression of PDS gene was higher in term than in first trimester pregnancy samples. In vitro, NIS gene was expressed at a high level in VCT obtained from first trimester pregnancy, and its expression decreased by 3- to 4-fold during the differentiation of VCT in VSCT. Expression of NIS was lower (up to 30-fold) in VCT obtained in placental samples from third trimester than from first trimester pregnancy. In contrast, the expression of PDS gene was low in VCT and increased by 5- to 10-fold during VSCT formation; this was observed in cells isolated from placental samples of both first trimester and term pregnancies. Immunohistochemical analysis showed that NIS protein was present on the entire membrane of VCT, whereas pendrin was mainly located at the brush border membrane of VSCT, facing the mother. In conclusion, 1) NIS and PDS genes are differently expressed in the placenta during gestation; and 2) whereas pendrin is expressed at the brush border membrane of syncytiotrophoblast cells, NIS protein is mainly located in the cytotrophoblast layer.