Medullary thyroid microcarcinoma: a clinicopathologic retrospective study of 38 patients with no prior familial disease

Thirty-eight patients (25 women, 13 men; mean age, 57.8 [32 to 91]) showing one or more medullary thyroid microcarcinomas (ie, < 1 cm), with no prior MEN II or medullary thyroid carcinoma history in their family, were reviewed. Follow-up was available for 29 patients (mean, 53.6 months [1 to 147]). 21 patients (72.4%) are alive and free of disease, four patients (13.8%) died during follow-up without disease, 2 patients are alive with disease (local recurrence and persistent hypercalcitoninemia) after 80 and 99 months, respectively, and 2 patients died of disease after 24 and 46 months. Most tumors were incidental pathological findings (19 of 38) or were discovered by systematic blood calcitonin measurement for a nodular thyroid disease (15 of 38). Only the four patients who had an unfavorable outcome were symptomatic cases (palpable micro-MTC, diarrhea, cervical lymph node metastasis and pulmonary metastatic disease). The two patients with metastatic disease at diagnosis died during follow-up. In univariate analysis, a symptomatic medullary thyroid carcinoma was a strong predictor of an unfavourable outcome (p < .00008), as were the preoperative calcitonin level (P = .007) and an elevated postoperative calcitonin level (P = .004). Among 30 histopathological criteria, only the presence of amyloid correlated with an unfavorable outcome (P = .018).

Radiosensitivity of human normal and tumoral thyroid cells using fluorescence in situ hybridization and clonogenic survival assay

PURPOSE

By using cell survival as a reference, we evaluated the radiosensitivity of human normal and tumoral thyroid cells using of radiation-induced translocations.

METHODS AND MATERIALS

Tissue samples were obtained from patients undergoing thyroidectomy. Cell cultures were established, irradiated with 60Co, and metaphases painted using commercial whole-chromosome 4 hybridization probe and pancentromeric probe. The clonogenic survival was assessed by conventional colony forming assay.

RESULTS

After irradiation, normal cultured thyroid cells yielded a higher number of translocations than cultures derived from adenomas or thyroid carcinoma. The colony forming assay demonstrated, by way of the mean inactivation dose, a higher survival of thyroid carcinoma and adenoma cells than of normal thyroid cells. This difference between tumoral and nontumoral cells is significant in each method (p = 0.0001), and cannot be explained by apoptosis in irradiated malignant cells. Correlation of the results obtained by both methods is shown by comparing the survival fraction at 2 Gy (SF2) and the percentage of chromosome 4 translocations at 2 Gy.

CONCLUSION

These results indicate that the yield of radiation-induced translocations serves as a good and rapid prediction of the intrinsic radiosensitivity of thyroid cells, and that this test could be applied to other tumors.

Gastroenteropancreatic neuroendocrine tumor metastases to the thyroid gland: differential diagnosis with medullary thyroid carcinoma

Neuroendocrine tumors (NET) of the thyroid gland are rare. Apart from medullary thyroid carcinoma (MTC), metastases of gastroenteropancreatic (GEP) NET may also occur. Features of six patients (five men, one female: age range, 39-67 years) with thyroid metastases from a GEP-NET are described. Thyroid metastases were bilateral in all patients and were associated with enlarged neck lymph nodes in five. In four cases, the thyroid tumor was either the first sign of the disease (n = 2) or was an isolated site of recurrence (n = 2). The tumors were well (n = 3) or poorly differentiated (n = 3). Five tumors for which the primary site could be determined corresponded to foregut-derived tumors (3 lungs, 1 thymus and 1 pancreatic NET). One tumor demonstrated calcitonin (CT) production as shown by immunohistochemistry and elevated plasma CT levels. However, the disease history and the clinical features strongly favored a metastasizing GEP-NET. No tumoral RET proto-oncogene mutation was found in this patient. The differential diagnosis between metastatic GEP-NET and MTC is crucial because prognosis, work-up, and treatment differ greatly.

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.

[Follicular carcinoma]

Thyroid follicular carcinoma are divided in three subgroups: 1) minimally invasive well differentiated encapsulated follicular carcinoma; 2) invasive well differentiated follicular carcinoma; 3) moderately differentiated follicular carcinoma. Usually diagnosis between encapsulated well differentiated follicular carcinoma and atypical adenoma is difficult. Apart the presence of metastases, histologic criteria to separate these entities are often insufficient. Insofar as all these tumours have a very good prognosis, we think that they could be brought together under the same terminology. Actual morphological differences would be expressed, like in some others localizations, in a histologic grading. This way of classifying appears more consistent with reality and could allow to assume in better conditions, diagnostic uncertainty which exists in this field.

Medullary thyroid carcinoma: search for histological predictors of survival (109 proband cases analysis)

A group of 13 pathologists belonging to the French Calcitonin Tumor Study Group (GETC: Groupe d'Etude des Tumeurs à Calcitonine) examined the histological slides and medical records of 109 proband cases of medullary thyroid carcinoma (MTC) diagnosed on clinical features. The cases belonged to the various forms of the disease (80 sporadic and 29 familial MTC). The aim of the study was to detect histological predictors for survival by comparing morphological data from patients killed by the disease versus the others. Twenty-seven histological parameters were considered, including cellular heterogeneity, shape of the cells, and cytoplasmic characteristics. Other parameters such as sex, age, and phenotype of the disease were also studied. First, predictive parameters of interest on survival function were selected by univariate analysis (Mantel-Cox test). Then, the extracted parameters were tested in a multifactorial analysis using the Cox's forward stepping proportional hazard model. Five parameters were significantly associated with a lower survival function: presence of necrosis in the tumor (P = .001), squamous pattern (P = .002), age over 45 years (P = .004), presence of oxyphil cells in the tumor and absence of cells with intermediate cytoplasm (P = .025), less than 50% of calcitonin immunoreactive cells in the tumor (P = .04).

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).

Microcarcinoma of the thyroid gland: the Gustave-Roussy Institute experience

BACKGROUND

Patients with thyroid microcarcinoma (TMC) have favorable long term prognoses. However, recurrences in the neck and distant metastases have been reported. The authors investigated independent factors associated with recurrence in an effort to define therapeutic guidelines.

METHODS

Two hundred eighty-one patients (207 females, 74 males; mean age, 41.9 years) with a differentiated thyroid carcinoma < or = 1 cm in greatest dimension (mean size +/- standard deviation, 5.9+/-3.3 mm) were analyzed. The median follow-up time was 7.3 years.

RESULTS

TMC diagnosis was incidental in 189 patients, and metastases were the first manifestation of the disease in the other 92 patients. Therapy included near-total thyroidectomy for 195 patients, lymph node dissection for 195, and therapeutic administration of radioiodine for 124. Eleven recurrences (3.9%) were observed 4.3+/-2.7 years (mean +/- standard deviation) after initial treatment: all had locoregional recurrence (4 in the thyroid bed and 7 in the lymph nodes), and in one of these the local recurrence was associated with lung metastases. Multivariate analysis showed that two parameters significantly influenced TMC recurrence, namely, the number of histologic foci (P < 0.002) and the extent of initial thyroid surgery (P < 0.01). Only 3.3% of patients with unifocal TMC treated with loboisthmusectomy had tumor recurrence.

CONCLUSIONS

The recurrence rate for TMC appears to be low (3.9%). In the authors' view, loboisthmusectomy is the treatment of choice for patients with TMC when only one focus of cancer is found histologically, and total thyroidectomy is the optimal treatment for patients with multiple foci.

Iodide symporter gene expression in human thyroid tumors

Expression of the Na+/I- symporter (NIS) gene was investigated by RT-PCR in a selected series of 26 primary thyroid carcinomas (19 papillary, 5 follicular, and 2 anaplastic). Fifteen follicular adenomas (11 "cold" and 4 "hot" adenomas) were also studied. Five of 19 papillary thyroid cancer did not express NIS messenger ribonucleic acid (mRNA). In all but 1 follicular cancer, NIS transcript was fully detected. In anaplastic tissue, NIS mRNA was only barely detected in 1 case. All of the follicular thyroid adenomas except 1 expressed the NIS gene. In contrast, all tumors studied excluding the anaplastic histotype fully expressed thyroglobulin and thyroid peroxidase mRNA transcripts. In 2 patients, a lower expression (3- to 5-fold) of NIS mRNA was found in metastasis by dot blot analysis compared with those in both normal and primary neoplastic thyroid tissue. Four of 8 differentiated thyroid cancer patients selected for the presence of metastases with negative posttherapy 131I total body scan showed the lack of NIS gene expression in their primary cancer. This defect, at least in these cases, is a somatic and intrinsic lesion of the primary cancer cells and is not due to a dedifferentiation process in the metastatic tissue. The early detection of the loss of NIS gene expression in the primary cancer, therefore, may provide useful information for the management of differentiated thyroid cancer patients.

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.

Development of medullary thyroid carcinoma in transgenic mice expressing the RET protooncogene altered by a multiple endocrine neoplasia type 2A mutation

Multiple endocrine neoplasia type 2 (MEN 2) is a dominantly inherited cancer syndrome that comprises three clinical subtypes: MEN type 2A (MEN-2A), MEN type 2B (MEN-2B), and familial medullary thyroid carcinoma (FMTC). Medullary thyroid carcinoma (MTC), a malignant tumor arising from calcitonin-secreting thyroid C cells, is the cardinal disease feature of this syndrome, and mortality in affected MEN-2 patients is mainly caused by this malignancy. Germ-line mutations of the RET protooncogene, which encodes a receptor tyrosine kinase, are responsible for these three neoplastic-prone disorders. MEN2 mutations convert the RET protooncogene in a dominantly acting oncogene as a consequence of the ligand-independent activation of the tyrosine kinase. The majority of MEN2A and FMTC mutations are located in the extracellular domain and cause the replacement of one of five juxtamembrane cysteines by a different amino acid. To examine whether expression of a MEN2A allele of RET results in transformation of C cells, we have used the transgenic approach. Expression of the RET gene altered by a MEN2A mutation was targeted in C cells by placing the transgene under the control of the calcitonin gene-related peptide/calcitonin promoter. Animals of three independent transgenic mouse lines, which expressed the transgene in the thyroid, displayed overt bilateral C cell hyperplasia as early as 3 weeks of age and subsequently developed multifocal and bilateral MTC. Moreover, these tumors were morphologically and biologically similar to human MTC which afflicts MEN2 individuals. These findings provide evidence that the MEN2A mutant form of RET is oncogenic in parafollicular C cells and suggest that these transgenic mice should prove a valuable animal model for hereditary MTC.

Targeted oncogenesis in the thyroid of transgenic mice

We have developed mouse models for tumors affecting the epithelial cellular compartment of the thyroid which has been targeted using the bovine thyroglobulin (bTg) promoter. Transgenic mice expressing the human activated c-Ha-Ras gene developed papillary thyroid carcinomas demonstrating the oncogenic potential of activated Ras gene in the thyroid gland. Transgenic mice express the mutant form of the alpha subunit of the adenylate cyclase-coupled G alpha s with mutations at codon 201 (R201H). The expression of this mutant transgene is not by itself sufficient to produce benign tumors or even hyperplasia, but the transgenic mice have inherited a predisposition to develop thyroid adenomas.

Iodine concentration by the thymus in thyroid carcinoma

A 14-yr-old boy underwent a total thyroidectomy with bilateral neck dissection for a papillary carcinoma with lymph node metastases. Total-body scanning with 3.7 GBq 131I revealed radioiodine accumulation in the anterior mediastinum. CT and MRI demonstrated a mediastinal mass which corresponded to the area of increased radioactivity. Five months later, another therapeutic dose of 131I was followed by a sternotomy and removal of the thymus because a hand-held radiodetecting surgical probe demonstrated that the thymus was the mediastinal structure which concentrated iodine. Thymus histology was negative for thyroid cancer metastases (as further confirmed by the negative immunostaining) and showed cystic Hassall's bodies. Secondary ion mass spectrometry microscopy demonstrated that iodine was located only in the Hassall's bodies, bound to proteins. This finding suggests that an acquired "thyroid follicle-like" structure, as that observed in cystic Hassall's bodies, could be responsible for the epithelial cell iodine uptake. In conclusion, we have provided evidence for the iodine-trapping property of the cystic Hassall's bodies of the thymus, which may be a possible cause of misleading mediastinal radioiodine uptake.

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.

Phenotypic and functional characterisation of tumour-infiltrating lymphocytes derived from thyroid tumours

The natural history of thyroid tumours and the hyper-reactivity of the immune system in patients with thyroid cancer suggest that immune surveillance may play a role in the control of this disease. A study was therefore undertaken to analyse the phenotypic and functional features of tumour-infiltrating lymphocytes (TILs) derived from thyroid tumours. In a series of experiments, it was found that, in contrast to TILs derived from patients with melanoma or renal cell carcinoma, thyroid TILs could be efficiently expanded in vitro only in the presence of allogeneic EBV transformed B (B. EBV) cells. Indeed, only one of the seven thyroid-derived TILs grew in vitro without feeder cells, whereas all 16 thyroid-derived TILs could be expanded in the presence of allogeneic B. EBV feeder cells. Phenotypic analysis of these TILs revealed a frequent in vitro expansion of an unusual T cell population that expressed both the CD4 and CD8 markers. Indeed, it was demonstrated that in five of 14 TILs in short-term culture (< day 23) and four of 11 TILs in long-term culture (> day 40), a lymphocyte population that coexpressed CD4 and CD8 antigen accounted for more than 15% of the total TIL population. This double-positive T cell population was not observed in TILs derived from melanoma or renal cell carcinoma. Thyroid-derived TILs also displayed an intense cytolytic activity against NK-sensitive tumour targets with 10 of 11 TILs exhibiting significant cytotoxicity towards the NK-sensitive K562 cell line. Six of 11 TILs were also cytotoxic towards autologous tumour, but when cold target inhibition with K562 was performed with three cultures, unlabelled K562 completely inhibited lysis of autologous tumour cells. A significant expansion of CD3+CD56+ T cells in the different TIL populations may explain this high level of NK-like cytotoxicity. In conclusion, TILs derived from thyroid tumours could be efficiently expanded in vitro under certain culture conditions. Different strategies must be explored to enhance their specific tumour autologous specificity, however, before they can be used in immunotherapy protocols.

[Ultrasonographic aspects of hepatic metastases of thyroid medullary cancers]

PURPOSE

The aim of this study was to describe the different ultrasonic features of hepatic metastases of medullary thyroid carcinoma and to point out two particular patterns.

MATERIAL AND METHOD

A retrospective review of the sonographic examinations of 35 patients with hepatic metastases from medullary thyroid carcinoma was performed. The metastases were classified relatively to their size and sonographic appearance.

RESULTS

Four ultrasonic types of metastases were described: Type I: small (< 3 cm) hyperechoic nodules with the same features as typical hepatic hemangioma (54%); Type II: markedly hyperechoic micronodules often associated with acoustic shadowing (40%); Type III: hyperechoic nodules of more than 3 cm in diameter (14%) corresponding to advanced intrahepatic disease; Type IV: hypoechoic or in target form nodules (28%) rarely isolated (8%), mostly associated with additional hyperechoic lesions (20%). Thirty two out of 35 patients had hyperechoic nodules; in 22 patients the HM were of a single type, mainly type I (n = 12) and in 13 patients different types of nodules were present. These sonographic features were correlated with the histologic characteristics of medullary thyroid carcinoma. No precise relationship could be establish between the histologic form of MTC and the US features.

CONCLUSION

The authors underline the possible mistake between the metastases of type I and the hemangioma and the characteristic appearance of metastases of type II.

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.

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.

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.

Radiolabeled somatostatin analog scintigraphy in differentiated thyroid carcinoma

After intravenous administration of a radiolabeled somatostatin analog (octreotide), an image of the thyroid gland is frequently observed; few data are available, however, on somatostatin receptors in epithelial thyroid cells assessed in vitro and on images of differentiated thyroid carcinoma (DTC) with pentetreotide scintigraphy.

METHODS

In four patients with metastatic thyroid carcinoma, whole-body scintigraphy was performed 4 to 48 hr after injection of 110 MBq of 111In-pentetreotide. The results were compared to data obtained with other imaging modalities, including scintigraphy performed after administration of a therapeutic dose of 131I.

RESULTS

There were positive foci in distant metastases on 111In-pentetreotide scintigraphy. Pentetreotide scintigraphy was positive in two patients with an "insular" form of DTC, one of whom had a positive (faintly) 131I scan. Of the other two patients with papillary DTC without radioiodine uptake, only one exhibited a certain degree of pentetreotide scintigraphy positivity in distant metastases.

CONCLUSION

These results show promise for exploration of insular thyroid carcinoma and suggest that these carcinomas may possess functional differentiation features, including somatostatin receptors.

Genetic alterations in thyroid hyperfunctioning adenomas

Thirty-seven thyroid autonomously hyperfunctioning adenomas were screened for mutations in the TSH receptor (TSHR), G alpha s (gsp), and ras genes. Polymerase chain reaction-amplified fragments of the TSHR C-terminal part (exon 10), the G alpha s (exons 8 and 9), and the three ras genes were obtained from the genomic DNA extracted from 37 tumors and their adjacent normal tissues and were studied by direct nucleotide sequencing and hybridization with synthetic probes. A point mutation in the third intracellular loop (codon 623) of the TSHR was found in 3 of 37 adenomas studied. This mutation codes for a change (Ala to Ser) in the TSHR structure and is somatic and heterozygotic. Constitutive activation of the TSHR was demonstrated by an increase in basal cAMP levels after transfection of Chinese hamster ovary cells with a mutated Ser623-TSHR complementary DNA. Nine gsp[00ae]MDRV[00af]- and one ras-activating mutations were also detected. No simultaneous alteration of the studied genes was present. Thus, in hyperfunctioning thyroid adenomas, our data suggest that a mutational activation of the TSHR and gsp genes may play a tumorigenic role through constitutive activation of the cAMP pathway.

Comparison of radiolabeled octreotide and meta-iodobenzylguanidine (MIBG) scintigraphy in malignant pheochromocytoma

METHODS

The results of in vivo somatostatin scintigraphy were correlated with those of MIBG from 14 patients, aged 22-66 yr, with metastatic pheochromocytoma (10 patients), malignant paraganglioma (3 patients) and metastatic ganglioneuroblastoma (1 patient). Twelve patients had elevated catecholamine excretion. A dynamic study and serial whole-body scans (4-48 hr) were obtained after injection of 130-187 MBq of 111In-DTPA-Phe-1-octreotide. When indicated, SPECT imaging was done. The results were compared to MIBG scans obtained after a diagnostic or a therapeutic dose.

RESULTS

Three patients with more than 20 tumor sites on MIBG scans had only 1-9 sites on 111In-octreotide scintigraphy. Two patients had no MIBG uptake but one had lung uptake on octreotide scintigraphy. In the other 9 patients with a total of 41 foci of MIBG uptake, 33 sites of 111In-octreotide uptake are found. All positive images with octreotide scintigraphy were seen at or before 4 hr, but the contrast improved at 24 hr. Uptake intensity was lower with 111In-octreotide than MIBG and the number of tumor sites was higher with MIBG. However, seven foci were positive only on octreotide scintigraphy and six of them could not be confirmed by other imaging modalities.

CONCLUSION

Use of octreotide to identify somatostatin receptors seems promising, especially when results from MIBG scans are negative. Moreover octreotide images could aid in determining a treatment regimen as well as establishing the extent of disease and prognosis.

Oncogenic potential of guanine nucleotide stimulatory factor alpha subunit in thyroid glands of transgenic mice

Transgenic mice have been used to address the issue of the oncogenic potential of mutant guanine nucleotide stimulatory factor (Gs) alpha subunit in the thyroid gland. The expression of the mutant Arg-201-->His Gs alpha subunit transgene has been directed to murine thyroid epithelial cells by bovine thyroglobulin promoter. The transgenic animals develop hyperfunctioning thyroid adenomas with increased intracellular cAMP levels and high uptake of [125I]iodine and produced elevated levels of circulating triiodothyronine and thyroxine. These animals demonstrate that the mutant form of Gs alpha subunit carries an oncogenic activity, thus supporting the model that deregulation of cAMP level alters growth control in thyroid epithelium. These animals represent models for humans with autonomously functioning thyroid nodules.