The phosphatidic acid phosphatase lipin-1 facilitates inflammation-driven colon carcinogenesis.

Colon cancer is a devastating illness that is associated with gut inflammation. Here, we explored the possible role of lipin-1, a phosphatidic acid phosphatase, in the development of colitis-associated tumorigenesis. Azoxymethane and dextran sodium sulfate-treated (DSS-treated) animals deficient in lipin-1 harbored fewer tumors and carcinomas than WT animals due to decreased cellular proliferation, lower expression of antiapoptotic and protumorigenic factors, and a reduced infiltration of macrophages in colon tumors. They also displayed increased resistance to DSS-induced colitis by producing less proinflammatory cytokines and experiencing less immune infiltration. Lipin-1-deficient macrophages from the colon were less activated and displayed lower phosphatidic acid phosphatase activity than WT macrophages isolated from DSS-treated animals. Transference of WT macrophages into lipin-1-deficient animals was sufficient to increase colitis burden. Furthermore, treatment of lipin-1-deficient mice with IL-23 exacerbated colon inflammation. Analysis of human databases from colon cancer and ulcerative colitis patients showed that lipin-1 expression is increased in those disorders and correlates with the expression of the proinflammatory markers CXCL1 and CXCL2. And finally, clinically, LPIN1 expression had prognostic value in inflammatory and stem-cell subtypes of colon cancers. Collectively, these data demonstrate that lipin-1 is a critical regulator of intestinal inflammation and inflammation-driven colon cancer development.

A new role of the Rac-GAP ß2-chimaerin in cell adhesion reveals opposite functions in breast cancer initiation and tumor progression.

ß2-chimaerin is a Rac1-specific negative regulator and a candidate tumor suppressor in breast cancer but its precise function in mammary tumorigenesis in vivo is unknown. Here, we study for the first time the role of ß2-chimaerin in breast cancer using a mouse model and describe an unforeseen role for this protein in epithelial cell-cell adhesion. We demonstrate that expression of ß2-chimaerin in breast cancer epithelial cells reduces E-cadherin protein levels, thus loosening cell-cell contacts. In vivo, genetic ablation of ß2-chimaerin in the MMTV-Neu/ErbB2 mice accelerates tumor onset, but delays tumor progression. Finally, analysis of clinical databases revealed an inverse correlation between ß2-chimaerin and E-cadherin gene expressions in Her2+ breast tumors. Furthermore, breast cancer patients with low ß2-chimaerin expression have reduced relapse free survival but develop metastasis at similar times. Overall, our data redefine the role of ß2-chimaerin as tumor suppressor and provide the first in vivo evidence of a dual function in breast cancer, suppressing tumor initiation but favoring tumor progression.

FOXM1 is a molecular determinant of the mitogenic and invasive phenotype of anaplastic thyroid carcinoma.

Anaplastic thyroid carcinoma (ATC) is a very aggressive thyroid cancer. forkhead box protein M1 (FOXM1) is a member of the forkhead box family of transcription factors involved in control of cell proliferation, chromosomal stability, angiogenesis, and invasion. Here, we show that FOXM1 is significantly increased in ATCs compared with normal thyroid, well-differentiated thyroid carcinomas (papillary and/or follicular), and poorly differentiated thyroid carcinomas (P=0.000002). Upregulation of FOXM1 levels in ATC cells was mechanistically linked to loss-of-function of p53 and to the hyperactivation of the phosphatidylinositol-3-kinase/AKT/FOXO3a pathway. Knockdown of FOXM1 by RNA interference inhibited cell proliferation by arresting cells in G2/M and reduced cell invasion and motility. This phenotype was associated with decreased expression of FOXM1 target genes, like cyclin B1 (CCNB1), polo-like kinase 1 (PLK1), Aurora B (AURKB), S-phase kinase-associated protein 2 (SKP2), and plasminogen activator, urokinase: uPA (PLAU). Pharmacological inhibition of FOXM1 in an orthotopic mouse model of ATC reduced tumor burden and metastasization. All together, these findings suggest that FOXM1 represents an important player in thyroid cancer progression to the anaplastic phenotype and a potential therapeutic target for this fatal cancer.

TWIST1 plays a pleiotropic role in determining the anaplastic thyroid cancer phenotype.

CONTEXT: Anaplastic thyroid carcinoma (ATC) is one of the most aggressive human tumors; it is characterized by chemoresistance, local invasion, and distant metastases. ATC is invariably fatal. OBJECTIVE: The aim was to study the role of TWIST1, a basic helix-loop-helix transcription factor, in ATC. DESIGN: Expression of TWIST1 was studied by immunohistochemistry and real-time PCR in normal thyroids and well-differentiated, poorly differentiated, and ATC. The function of TWIST1 was studied by RNA interference in ATC cells and by ectopic expression in well-differentiated thyroid carcinoma cells. RESULTS: ATCs up-regulate TWIST1 with respect to normal thyroids as well as to poorly and well-differentiated thyroid carcinomas. Knockdown of TWIST1 by RNA interference in ATC cells reduced cell migration and invasion and increased sensitivity to apoptosis. The ectopic expression of TWIST1 in thyroid cells induced resistance to apoptosis and increased cell migration and invasion. CONCLUSIONS: TWIST1 plays a key role in determining malignant features of the anaplastic phenotype in vitro.

BRAF mutation associated with other genetic events identifies a subset of aggressive papillary thyroid carcinoma.

PURPOSE: BRAF(V600E) mutation represents the most common oncogenic event in sporadic papillary thyroid cancer (PTC). There are, however, significant discrepancies regarding the overall frequency, its prevalence in PTC-variants, and its relationship with clinico-pathological parameters of poor outcome. Moreover, the impact of BRAF(V600E) mutants on tumour-related patient's death has not been evaluated. DESIGN: We analysed, by PCR-SSCP and/or PCR-direct sequencing, exons 8, 10, 11 and 15 of BRAF in 113 tumour samples from 49 PTC-patients. Matched lymph node metastases and/or distant metastases (DMs) were screened in 35 patients. Focal changes in the growth pattern or microscopic grade within the primary tumour (Pt) or the metastases were separately genotyped. Mutations at H-, K-, N-ras and PIK3CA exons 9 and 20 were also investigated. For comparison with PTC cases, the BRAF and Ras mutational status was evaluated in 89 specimens obtained from 24 poorly differentiated thyroid carcinomas (PDCs) and 36 anaplastic thyroid carcinomas (ATCs). RESULTS: BRAF(V600E) was found in 13/16 classical PTCs (CL-PTCs), 6/17 follicular variant PTCs (FV-PTCs) and 8/16 mixed (papillary/follicular) PTCs (Mx-PTCs), being significantly associated with CL-PTCs (P = 0.015). BRAF(V600E) segregated with metastatic PTC-cells in 43% of the patients, but only one DM disclosed the mutation. PTC-tumours featuring concurrent less-differentiated foci were BRAF wild-type in both components. Noteworthy, the frequency of BRAF mutations among PDCs and ATCs resulted considerably lower (16.6% and 25%, respectively) than in PTCs (55%). The prevalence of Ras mutations among PDCs and ATCs (46% and 36%, respectively) was, however, much higher than in PTCs (14%). Five (71%) of the patients who died of PTC displayed somatic mutations. Four of them had other gene alteration associated with BRAF(V600E) and the only one that did not, BRAF(V600E) was restricted to the Pt. The occurrence of BRAF(V600E) associated with other genetic events was an independent predictor of DMs during follow-up, recurrence and tumour-related death. Remarkably, two PDCs (8.3%) and five ATCs (14%) revealed concurrent BRAF and Ras mutations. CONCLUSION: BRAF(V600E)'alone' does not represent a marker for poor outcome, however, when associated with alterations in other genes identifies a subset of PTCs with increased risk of recurrence and decreased survival.

High frequency of germline succinate dehydrogenase mutations in sporadic cervical paragangliomas in northern Spain: mitochondrial succinate dehydrogenase structure-function relationships and clinical-pathological correlations.

PURPOSE: Germline SDHB, SDHC, and/or SDHD mutations have been reported in familial and apparently sporadic paragangliomas (PGLs). There is, however, some variation in the prevalence, penetrance, and phenotypic expression of the succinate dehydrogenase (SDH) mutated gene among different populations. We sought to determine whether germline mutations in SDHB, SDHC, and/or SDHD play a role in cervical PGLs from northern Spain, where this disorder is particularly frequent, and whether there is any difference with respect to the data published in other populations. DESIGN: Thirty-six sporadic cervical PGLs and four familial PGLs were investigated by PCR-single-strand conformation polymorphism analysis and sequencing. Computational biology was applied to address the structural-conformational changes behind missense mutations and, simultaneously, infer the possible consequences in protein function. RESULTS: Eight sporadic cases (22.2%) carried pathogenic germline mutations, six of which were in SDHB and two in SDHD. Three families had mutations in SDHD and one in SDHB. Seven of 11 different pathogenic mutations (64%) affected SDHB. Ten mutations were novel. Missense mutations were primarily found in SDHB and frameshift mutations in SDHD. Missense SDHB mutations seemed to alter the enzymatic activity by hampering the electron transfer. SDH-linked tumors occurred mainly in males (P = 0.0033), occurred at a younger age (P < 0.0001), were usually multifocal (P = 0.0011), and exhibited a larger size (P = 0.0341). CONCLUSIONS: A significant proportion of sporadic cervical PGLs arise as a consequence of intrinsic genetic factors. At variance with previous reports, SDHB is frequently mutated in sporadic cervical PGLs and the mutations do not entail a deleterious behavior. Therefore, SDHB genetic testing may be considered in all subjects presenting with solitary cervical PGL and no family history.

[Head and neck paragangliomas: revision of 89 cases in 73 patients]. / Paragangliomas de cabeza y cuello: revisión de 89 casos en 73 pacientes.

INTRODUCTION: Paragangliomas (PGL) are uncommon neuroectodermal tumours. PGL are usually clinically benign tumours, although metastasis has been reported and invasive growth can occur in adjacent tissues (<10 %). Mutations in SDHB, SDHC, and SDHD, which encode sub-units of mitochondrial complex II (succinate dehydrogenase), play an important role in the pathogenesis of these tumours. MATERIAL AND METHOD: Retrospective review of 73 patients with 89 paragangliomas who had undergone resection of the PGL in our hospital. There were 8 patients who displayed multiple PGL. PGL were distributed as follows: 33 were jugular, 17 tympanic, 26 carotid body tumours, and 13 vagal paragangliomas. All these patients had a follow-up time of at least a year. The surgical approach was evaluated in terms of tumour origin, sequelae, and subsequent evolution, as well as the relapses and their relation with location of the primary tumour. RESULTS: The treatment was surgical, using complementary radiosurgery in just 1 patient. The type A infratemporal fossa approach was used in jugular paragangliomas, the approach was cervical in the carotid and vagal ones and, in the tympanics, a transmeatal or transmastoid approach was performed. In the 73 patients making up our study group, there were 11 recurrences which appeared in jugular paragangliomas (two of them in multiple PGL cases). The post-operative sequelae were mainly cranial nerve paralysis (VII, IX, X, XI, and XII), along with cerebrospinal fluid fistulas in 14 of the jugular PGLs. CONCLUSIONS: With this article we try to reflect our experience in the treatment of this type of tumour. Surgical treatment achieves excellent control of the disease with an acceptable morbidity in young or middle-aged patients. In order to diminish the probabilities of facial nerve paralysis in jugular PGL we must avoid the facial nerve transposition in the infratemporal approach.

Paragangliomas de cabeza y cuello: revisión de 89 casos en 73 pacientes / Head and neck paragangliomas: revision of 89 cases in 73 patients

Introducción: Los paragangliomas son tumores poco frecuentes de origen neuroectodérmico. Se los considera tumores benignos, pero en algunas ocasiones tienen un comportamiento biológico similar a los tumores malignos (< 10 %). Las mutaciones germinales en los genes SDHB, SDHC y SDHD, que codifican las subunidades del mismo nombre en el complejo enzimático mitocondrial de la succinato deshidrogenasa, tienen un papel importante en la patogenia. Material y método: Se trata de un estudio retrospectivo en el que se revisa a 73 pacientes intervenidos en nuestro servicio con un total de 89 paragangliomas, ya que 8 pacientes presentaban paragangliomas múltiples. Los paragangliomas se distribuyeron de la siguiente forma: 33 yugulares, 17 timpánicos, 26 carotídeos y 13 vagales. Todos estos pacientes tuvieron un seguimiento mínimo de 1 año. Se evaluaron las vías de abordaje en función de la localización tumoral, las secuelas acaecidas y su ulterior evolución, así como las recurrencias y su relación con la localización del tumor primario. Resultados: El tratamiento fue quirúrgico, utilizando la radiocirugía como tratamiento complementario en un paciente. En los paragangliomas yugulares se realizó un abordaje infratemporal tipo A, en los carotídeos y vagales el abordaje fue cervical y en los timpánicos, transmeatal o transmastoideo. De los 73 pacientes con paragangliomas intervenidos que componen nuestra población en estudio, hubo 11 recurrencias, que aparecieron en los paragangliomas yugulares, que en 2 casos fueron paragangliomas múltiples. Las secuelas postoperatorias fueron sobre todo la parálisis de nervios craneales (VII, IX, X, XI y XII), junto con las fístulas de líquido cefalorraquídeo en el 14 % de los paragangliomas yugulares. Conclusiones: Con este artículo pretendemos reflejar nuestra experiencia en el tratamiento de este tipo de tumores. El tratamiento quirúrgico consigue un excelente control de la enfermedad con una morbilidad aceptable en pacientes de mediana edad o jóvenes. Para disminuir las probabilidades de parálisis facial en los paragangliomas yugulares, debe evitarse la transposición del facial en el abordaje infratemporal de la fosa yugular

Introduction: Paragangliomas (PGL) are uncommon neuroectodermal tumours. PGL are usually clinically benign tumours, although metastasis has been reported and invasive growth can occur in adjacent tissues (<10 %). Mutations in SDHB, SDHC, and SDHD, which encode sub-units of mitochondrial complex II (succinate dehydrogenase), play an important role in the pathogenesis of these tumours. Material and method: Retrospective review of 73 patients with 89 paragangliomas who had undergone resection of the PGL in our hospital. There were 8 patients who displayed multiple PGL. PGL were distributed as follows: 33 were jugular, 17 tympanic, 26 carotid body tumours, and 13 vagal paragangliomas. All these patients had a follow-up time of at least a year. The surgical approach was evaluated in terms of tumour origin, sequelae, and subsequent evolution, as well as the relapses and their relation with location of the primary tumour. Results: The treatment was surgical, using complementary radiosurgery in just 1 patient. The type A infratemporal fossa approach was used in jugular paragangliomas, the approach was cervical in the carotid and vagal ones and, in the tympanics, a transmeatal or transmastoid approach was performed. In the 73 patients making up our study group, there were 11 recurrences which appeared in jugular paragangliomas (two of them in multiple PGL cases). The post-operative sequelae were mainly cranial nerve paralysis (VII, IX, X, XI, and XII), along with cerebrospinal fluid fistulas in 14 of the jugular PGLs. Conclusions: With this article we try to reflect our experience in the treatment of this type of tumour. Surgical treatment achieves excellent control of the disease with an acceptable morbidity in young or middle-aged patients. In order to diminish the probabilities of facial nerve paralysis in jugular PGL we must avoid the facial nerve transposition in the infratemporal approach

Mutation of the PIK3CA gene in anaplastic thyroid cancer.

The phosphatidylinositol 3'-kinase (PI3K) pathway is frequently activated in thyroid carcinomas through the constitutive activation of stimulatory molecules (e.g., Ras) and/or the loss of expression and/or function of the inhibitory PTEN protein that results in Akt activation. Recently, it has been reported that somatic mutations within the PI3K catalytic subunit, PIK3CA, are common (25-40%) among colorectal, gastric, breast, ovarian cancers, and high-grade brain tumors. Moreover, PIK3CA mutations have a tendency to cluster within the helical (exon 9) and the kinase (exon 20) domains. In this study, 13 thyroid cancer cell lines, 80 well-differentiated thyroid carcinomas of follicular (WDFC) and papillary (WDPC) type, and 70 anaplastic thyroid carcinomas (ATC) were investigated, by PCR-direct sequencing, for activating PIK3CA mutations at exons 9 and 20. Nonsynonymous somatic mutations were found in 16 ATC (23%), two WDFC (8%), and one WDPC (2%). In 18 of the 20 ATC cases showing coexisting differentiated carcinoma, mutations, when present, were restricted to the ATC component and located primarily within the kinase domain. Three cell lines of papillary and follicular lineage (K1, K2, and K5) were also found mutated. In addition, activation of Akt was observed in most of the ATC harboring PIK3CA mutations. These findings indicate that mutant PIK3CA is likely to function as an oncogene among ATC and less frequently well-differentiated thyroid carcinomas. The data also argue for a role of PIK3CA targeting in the treatment of ATC patients.

Mitogenic effects of the up-regulation of minichromosome maintenance proteins in anaplastic thyroid carcinoma.

CONTEXT: Anaplastic thyroid carcinomas (ATC) are among the most aggressive human malignancies and are characterized by high mitotic activity. Minichromosome maintenance proteins (MCM) 2-7 are required to initiate eukaryotic DNA replication, and their overexpression has been associated with dysplasia and malignancy. OBJECTIVE: In an attempt to cast light on the mechanisms governing ATC, we evaluated MCM5 and MCM7 expression in human normal, papillary (PTC), and anaplastic thyroid samples, as well as in primary culture cells and transgenic mouse models. RESULTS: MCM5 and MCM7 expression was high in 65% of ATC and negligible in normal thyroid tissue and papillary thyroid carcinomas. In ATC, high MCM5 and MCM7 expression was paralleled by high levels of MCM2 and MCM6. An analysis of human ATC primary cell cultures and of a transgenic mouse model of ATC confirmed these findings. An increased transcription rate accounted for MCM7 up-regulation, because the activity of the MCM7 promoter was more than 10-fold higher in ATC cells compared with normal thyroid cells. Adoptive overexpression of wild-type p53, but not of its inactive (R248W and R273H) mutants, strongly down-regulated transcription from the MCM7 promoter, suggesting that p53 knock-out contributes to MCM7 up-regulation in ATC. Treatment with small inhibitory duplex RNAs, which decrease MCM7 protein levels, reduced the rate of DNA synthesis in ATC cells. CONCLUSION: MCM proteins are overexpressed in ATC and sustain the high proliferative capacity of ATC cells.

Hürthle (oncocytic) cell tumors of thyroid: etiopathogenesis, diagnosis and clinical significance.

The etiopathogenesis and the classification of oncocytic (Hürthle cell) tumors of the thyroid is reviewed with an emphasis on the role played by mitochondrial and nuclear genetic abnormalities that interfere with mitochondrial function. Oxyphilia is classified into primary or secondary and the so-called Hürthle cell carcinoma is divided into oncocytic (Hürthle cell) variants of papillary and follicular carcinoma.

ras mutations are associated with aggressive tumor phenotypes and poor prognosis in thyroid cancer.

PURPOSE: ras oncogenic activation has long been demonstrated in thyroid carcinomas of follicular cell derivation, but no consistent relationship has been shown between mutations and clinicopathologic features. MATERIALS AND METHODS: We analyzed H-, K-, and N-ras mutations by polymerase chain reaction-single-strand conformational polymorphism followed by DNA sequencing in 125 thyroid carcinoma specimens from 107 patients, to include tumors covering the entire spectrum of thyroid tumor differentiation. RESULTS: Mutations were identified in four (8.2%) of 49 well-differentiated carcinomas (WDCs; two [6.7%] of 30 of the tumors were papillary carcinomas, two [10.5%] of 19 of them were follicular carcinomas), in 16 (55.2%) of 29 poorly differentiated carcinomas (PDCs), and in 15 (51.7%) of 29 undifferentiated carcinomas, with a significant association between ras mutation and poorly or undifferentiated tumors (P <.001). Twenty-six (74.3%) of 35 patients with ras-mutated tumors died as a result of disease as opposed to 23 (31.9%) of 72 patients with tumors lacking the mutations. Among patients with differentiated thyroid carcinomas (WDC and PDC), 11 (55.0%) of 20 patients with mutated tumors died as a result of disease as opposed to nine (15.5%) of 58 patients with wild-type ras tumors, and the correlation was independent of tumor differentiation and stage (P =.016). K-ras codon 13 mutations (all with G-A nucleotide transitions resulting in Gly>Asp substitution) and single activating mutations in any of the ras genes were also independent predictors of poor survival in differentiated thyroid carcinomas (P =.027 and P =.007, respectively). CONCLUSION: These findings demonstrate that ras mutations are a marker for aggressive cancer behavior and indicate a possible role of ras genotyping to identify thyroid carcinoma subsets associated with poor prognosis.

Abnormalities of the APC/beta-catenin pathway in endometrial cancer.

The activation of the APC/beta-catenin signalling pathway due to beta-catenin mutations has been implicated in the development of a subset of endometrial carcinomas (ECs). However, up to 25% of ECs have beta-catenin nuclear accumulation without evidence of beta-catenin mutations, suggesting alterations of other molecules that can modulate the Wnt pathway, such as APC, gamma-catenin, AXIN1 and AXIN2. We investigated the expression pattern of beta- and gamma-catenin in a group of 128 endometrial carcinomas, including 95 endometrioid endometrial carcinomas (EECs) and 33 non-endometrioid endometrial carcinomas (NEECs). In addition, we evaluated the presence of loss of heterozygosity and promoter hypermethylation of the APC gene and mutations in the APC, beta- and gamma-catenin, AXIN1, AXIN2, and RAS genes, and phospho-Akt expression. No APC mutations were detected but LOH at the APC locus was found in 24.3% of informative cases. APC promoter 1A hypermethylation was observed in 46.6% of ECs, and was associated with the endometrioid phenotype (P=0.034) and microsatellite instability (P=0.008). Neither LOH nor promoter hypermethylation of APC was associated with nuclear catenin expression. Nuclear beta-catenin expression was found in 31.2% of EECs and 3% of NEECs (P=0.002), and was significantly associated with beta-catenin gene exon 3 mutations (P<0.0001). beta-catenin gene exon 3 mutations were associated with the endometrioid phenotype, and were detected in 14 (14.9%) EECs, but in none of the NEECs (P=0.02). gamma-catenin nuclear expression was found in 10 ECs; it was not associated with the histological type but was associated with more advanced stages (P=0.042). No mutations in gamma-catenin, AXIN1 and 2 genes were detected in this series. Neither RAS mutations nor phospho-Akt expression, which were found in 16 and 27.6% of the cases, respectively, were associated with beta-catenin nuclear expression. Our results demonstrated a high prevalence of alterations in molecules of the APC/beta-catenin pathway, but only mutations in beta-catenin gene are associated with aberrant nuclear localization of beta-catenin.

Assessment of RET/PTC oncogene activation and clonality in thyroid nodules with incomplete morphological evidence of papillary carcinoma: a search for the early precursors of papillary cancer.

Noninvasive thyroid nodules that exhibit borderline morphological signs of papillary cancer are difficult to diagnose and we do not know if they represent papillary carcinoma precursor lesions. Forty-six such nodules were analyzed for RET activation by immunohistochemistry and, in selected cases, by reverse transcriptase-polymerase chain reaction performed on RNA extracted after laser capture microdissection (LCM) of the tumor foci with and without papillary carcinoma features and positive RET immunoreactivity. RET immunoreactivity was identified, at least focally, in 30 of 46 (65.2%) of the nodules where it closely paralleled the morphological changes. Enough RNA was obtained after LCM in seven samples. RET/PTC1 or RET/PTC3 were detected in microscopic foci with papillary carcinoma features in most of the thyroid nodules (five of seven cases). No RET/PTC1 or RET/PTC3 rearrangements were detected in areas of the same tumors that lacked the cytological alterations. Analysis of clonality in the same nodules selected for LCM demonstrated that two were monoclonal and six were polyclonal. We conclude that RET activation closely parallels the morphological changes, that it is restricted to those areas of the tumor with the cytological alterations and that it is detectable in both mono- and polyclonal tumors. Although the finding of microscopic foci indicative of papillary carcinoma in a hyperplastic or adenomatous nodule does not justify the interpretation of the entire lesion as papillary carcinoma, it is possible that such foci may precede the development of invasive papillary cancer.

RET activation and clinicopathologic features in poorly differentiated thyroid tumors.

Poorly differentiated carcinoma of the thyroid gland (PDC) represents an heterogeneous group of epithelial neoplasms with morphologic features and clinical characteristics intermediate between well differentiated and anaplastic (undifferentiated) carcinomas. Unlike well differentiated tumors, PDCs are associated with significant morbidity and mortality. The general prevalence of RET/PTC rearrangement in thyroid PDC and its impact on patient outcome are unknown. To address these issues and to identify prognostically relevant clinicopathologic parameters, we have investigated a series of 62 PDCs. RET/PTC rearrangement, analyzed by RT-PCR and immunohistochemistry using antibodies specific for the tyrosine kinase and juxtamembrane portions of the RET protein, was identified in 8/62 (12.9%) PDCs. RET/PTC was more common in cases with histologic evidence indicating coexistence with or possible evolution from a well differentiated papillary carcinoma (5 of 25 tumors, 20%) but did not correlate with other clinicopathologic parameters. The relatively low prevalence of RET activation in PDCs argues against a major role for RET/PTC in the progression from well to poorly differentiated thyroid tumor phenotypes. Survival analysis demonstrates that poor survival in PDC is associated with old age, male sex, invasion of extrathyroidal soft tissues, coexistence in the same tumor of oncocytic features with insular growth pattern, and distant metastases but not RET activation.