Preoperative Evaluation of Thyroid Cancer: A Review of Current Best Practices

OBJECTIVE

The incidence of thyroid cancer has significantly increased in recent decades. Although most thyroid cancers are small and carry an excellent prognosis, a subset of patients present with advanced thyroid cancer, which is associated with increased rates of morbidity and mortality. The management of thyroid cancer requires a thoughtful individualized approach to optimize oncologic outcomes and minimize morbidity associated with treatment. Because endocrinologists usually play a key role in the initial diagnosis and evaluation of thyroid cancers, a thorough understanding of the critical components of the preoperative evaluation facilitates the development of a timely and comprehensive management plan. The following review outlines considerations in the preoperative evaluation of patients with thyroid cancer.

METHODS

A clinical review based on current literature was generated by a multidisciplinary author panel.

RESULTS

A review of considerations in the preoperative evaluation of thyroid cancer is provided. The topic areas include initial clinical evaluation, imaging modalities, cytologic evaluation, and the evolving role of mutational testing. Special considerations in the management of advanced thyroid cancer are discussed.

CONCLUSION

Thorough and thoughtful preoperative evaluation is critical for formulating an appropriate treatment strategy in the management of thyroid cancer.

γδ T Cells Promote Steatohepatitis by Orchestrating Innate and Adaptive Immune Programming

BACKGROUND AND AIMS

The recruitment and activation of inflammatory cells in the liver delineates the transition from hepatic steatosis to steatohepatitis (SH).

APPROACH AND RESULTS

We found that in SH, γδT cells are recruited to the liver by C-C chemokine receptor (CCR) 2, CCR5, and nucleotide-binding oligomerization domain-containing protein 2 signaling and are skewed toward an interleukin (IL)-17A⁺ phenotype in an inducible costimulator (ICOS)/ICOS ligand-dependent manner. γδT cells exhibit a distinct Vγ4⁺ , PD1⁺ , Ly6C⁺ CD44⁺ phenotype in SH. Moreover, γδT cells up-regulate both CD1d, which is necessary for lipid-based antigens presentation, and the free fatty acid receptor, CD36. γδT cells are stimulated to express IL-17A by palmitic acid and CD1d ligation. Deletion, depletion, and targeted interruption of γδT cell recruitment protects against diet-induced SH and accelerates disease resolution.

CONCLUSIONS

We demonstrate that hepatic γδT cells exacerbate SH, independent of IL-17 expression, by mitigating conventional CD4⁺ T-cell expansion and modulating their inflammatory program by CD1d-dependent vascular endothelial growth factor expression.

SUN-284 DICER1 Mutations in Adolescent Girls: Clinicopathological Findings and Genetic Correlation

Background: The DICER1 syndrome is a rare tumor predisposition disorder associated with multinodular goiter (MNG), differentiated thyroid cancer, ovarian Sertoli-Leydig cell tumor, pleuropulmonary blastoma and pituitary blastoma (1,2). The DICER1 gene encodes the endoribonuclease protein of the ribonuclease III family which acts post-transcriptionally to downregulate messenger RNAs. Both germline and somatic mutations have been reported (3). We describe 2 previously healthy unrelated females referred for evaluation of thyroid nodules. Cases:Case 1: A 16yo female presented with spontaneous passage of polyps at her menstrual period. Histologic analysis revealed embryonal rhabdomyosarcoma. Her primary malignancy, confined to the cervix, was treated with surgical resection followed by chemotherapy. Staging evaluation revealed a left thyroid nodule. FNA of the nodule showed follicular patterned lesion with cytologic atypia; molecular testing was positive for DICER1 somatic mutation (c.5429A;p.D1810V). Peripheral blood genetic testing was positive for a heterozygous DICER1 germline mutation (1510-1G>A). She underwent left lobectomy; histology showed encapsulated papillary carcinoma. Case 2: A 13yo female developed a sudden non-tender neck mass. Ultrasound-guided FNA of the solid lesion in the left thyroid lobe revealed atypia of undetermined significance. Molecular studies identified a DICER1 gene mutation (c.5126A>G; p.D1709G). A peripheral blood sample showed heterozygous DICER1 mutation (c.1870C>T;pArg624*). Three 1^st degree family members were also positive for the germline mutation. She underwent total thyroidectomy; pathology revealed MNG with a predominant hyperplastic nodule. Conclusion: Two adolescents with thyroid lesions were positive for DICER1 mutations (4). The prevalence of DICER1 mutations, natural history, and extent of phenotypic heterogeneity are unknown. Two mutations, one germline and one somatic, were identified in our patients. Enhanced molecular testing (ThyroSeqv3) is now available to identify mutations. Testing thyroid nodules for DICER1 mutations (5-7), followed by screening for germline mutations in positive cases is essential to identify patients at risk of other manifestations and to ensure surveillance. Scrutiny of cases will help elucidate the natural history of DICER1 syndrome and establish guidelines regarding the extent and frequency of screening. References 1. Wasserman J, et al. JCEM 2018; 103: 2009. 2. Van Engelen K, et al. PBC 2018; 65:e26720. 3. Robertson JC, et al. Cancers (Basel) 2018; 10: pii: E143. 4. Nikiforova MN, et al., Cancer. 2018;124:1682. 5. Rutter M, et al. JCEM 2016; 101: 1. 6. Cai S, et al. JPHO 2017; 39: 355. 7. van der Tuin K, et al. JCEM 2018 Sep 26 [Epub ahead of print].

MON-570 Clinical Utility of ThyroSeq v3 Genomic Classifier Test in Detecting Gene Fusions in Thyroid Nodules

Background: Chromosomal rearrangements leading to gene fusions are a known molecular mechanism of thyroid cancer. ThyroSeq Genomic Classifier (GC) allows detecting most of the known fusion types preoperatively by analyzing thyroid fine-needle aspiration (FNA) samples collected from thyroid nodules, but it also facilitates discovery of novel fusion types. The goal of this study was to evaluate the prevalence and types of known and novel fusions detected in thyroid nodules during routing clinical testing and establish histopathologic and clinical correlations. Design: Overall, 6,800 consecutive thyroid nodules were tested by a targeted next-generation sequencing assay (ThyroSeq v3 GC) using material collected by fine-needle aspiration (FNA). In addition, 17 surgically removed tumors were tested for confirmation of fusion subtype. Surgical pathology and clinical follow-up was obtained when available. Immunohistochemistry was performed on selected cases. Results: Gene fusions were identified in 318 (4.68%) of consecutively tested thyroid nodules. The most common fusion type was THADA/IGF2BP3 detected in 121 (38%) cases, followed by RET/PTC in 52 (16%), NTRK3 in 47 (15%), and PPARG in 47 (15%). Other fusions were found at lower prevalence, including BRAF in 14 (4%), ALK in 9 (3%), THADA/TRA2A in 8 (3%), and NTRK1 in 8 (3%) cases. In addition, 12 (4%) of nodules had rare and novel fusions, including PAX8/GLIS fusions. Presence of PAX8/GLIS fusions was confirmed in resected tumor samples. Surgical pathology information was collected on 49 (16%) positive cases and is ongoing. RET/PTC, NTRK3, NTRK1, and ALK fusions were all diagnosed as classic papillary thyroid carcinoma (PTC) or follicular variant of PTC. All 3 ALK-positive PTC and 5 THADA/IGF2BP3 NIFTP showed strong and diffuse immunoreactivity with ALK and IMP3 antibodies, respectively. THADA/IGF2BP3 was found in noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) (50%), PTC (40%) and follicular thyroid carcinoma (FTC) (10%). PPARG fusions were found in FTC (25%), Hurthle cell carcinoma (25%), PTC (25%) and follicular adenomas (25%). One BRAF fusion (SND1/BRAF) was found in follicular adenoma and all other nodules were PTC. All PAX8/GLIS fusions were characteristic of hyalinizing trabecular tumors. Conclusions: ThyroSeq GC detected gene fusions in approximately 5% of thyroid nodules that underwent FNA. ThyroSeq overall correct call rate for fusions was 94.1%, with variation between specific fusion types. Preoperative detection of fusions in FNA samples assists with diagnosis of thyroid nodules and thyroid cancer and informs patient management.

Targeting SYK signaling in myeloid cells protects against liver fibrosis and hepatocarcinogenesis

Liver fibrosis and fibrosis-associated hepatocarcinogenesis are driven by chronic inflammation and are leading causes of morbidity and death worldwide. SYK signaling regulates critical processes in innate and adaptive immunity, as well as parenchymal cells. We discovered high SYK expression in the parenchymal hepatocyte, hepatic stellate cell (HSC), and the inflammatory compartments in the fibrotic liver. We postulated that targeting SYK would mitigate hepatic fibrosis and oncogenic progression. We found that inhibition of SYK with the selective small molecule inhibitors Piceatannol and PRT062607 markedly protected against toxin-induced hepatic fibrosis, associated hepatocellular injury and intra-hepatic inflammation, and hepatocarcinogenesis. SYK inhibition resulted in increased intra-tumoral expression of the p16 and p53 but decreased expression of Bcl-xL and SMAD4. Further, hepatic expression of genes regulating angiogenesis, apoptosis, cell cycle regulation, and cellular senescence were affected by targeting SYK. We found that SYK inhibition mitigated both HSC trans-differentiation and acquisition of an inflammatory phenotype in T cells, B cells, and myeloid cells. However, in vivo experiments employing selective targeted deletion of SYK indicated that only SYK deletion in the myeloid compartment was sufficient to confer protection against fibrogenic progression. Targeting SYK promoted myeloid cell differentiation into hepato-protective TNFα^low CD206^hi phenotype downregulating mTOR, IL-8 signaling and oxidative phosphorylation. Collectively, these data suggest that SYK is an attractive target for experimental therapeutics in treating hepatic fibrosis and oncogenesis.

AHNS Series: Do you know your guidelines? AHNS Endocrine Section Consensus Statement: State-of-the-art thyroid surgical recommendations in the era of noninvasive follicular thyroid neoplasm with papillary-like nuclear features

The newly introduced pathologic diagnosis of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) will result in less bilateral thyroid surgery as well as deescalation in T4 suppressive and radioactive iodine treatment. Although, NIFTP is a nonmalignant lesion that has nuclear features of some papillary malignancies, the challenge for the surgeon is to identify a lesion as possibly NIFTP before the pathologic diagnosis. NIFTP, due to its reduction of overall rates of malignancy, will result in the initial surgical pendulum swinging toward lobectomy instead of initial total thyroidectomy. This American Head and Neck Society endocrine section consensus statement is intended to inform preoperative evaluation to attempt to identify those patients whose final pathology report may ultimately harbor NIFTP and can be offered a conservative surgical plan to assist in cost-effective, optimal management of patients with NIFTP.

Mutation in BRAF and Other Members of the MAPK Pathway in Papillary Thyroid Carcinoma in the Pediatric Population

CONTEXT

Papillary thyroid carcinoma (PTC) is an uncommon tumor in the pediatric population. A limited number of studies have examined genetic mutations affecting the mitogen-activated protein kinase (MAPK) pathway in the pediatric population.

OBJECTIVE

To examine mutations affecting this pathway in PTC in our pediatric population and compare the BRAF V600E mutation rates in pediatric and adult tumors.

DESIGN

Eighty-four patients, including 14 pediatric and 70 adult, with PTC were tested for the BRAF V600E mutation by using real-time polymerase chain reaction and sequencing. Additionally, we examined the rate of RAS point mutations with real-time polymerase chain reaction and rearrangements of RET/PTC1 and RET/PTC3 in the pediatric group with fluorescence in situ hybridization. Clinical and histologic data were compared as well.

RESULTS

Of 77 tumors that had an interpretable result, the BRAF V600E mutant was identified in 4 of 13 pediatric patients (31%) and 43 of 64 adult patients (67%), which was a significant difference (using Fisher exact test, P = .03). One pediatric and 6 adult cases did not reveal an interpretable result with melting curve analysis. One of these cases harbored a rare 3-base pair deletion mutation (c.1799_1801delTGA). Mutations in RAS genes were not seen in any pediatric tumors. One tumor with a RET/PTC1 rearrangement and another with RET/PTC3 were identified in the pediatric population (15%).

CONCLUSIONS

The rate of the BRAF V600E mutation in the pediatric population is significantly lower than that seen in the adult population. Mutations in RAS do not contribute significantly to pediatric PTC. This experience from our institution adds to the growing body of knowledge regarding tumor genetics in pediatric PTC.

Ewing sarcoma of the thyroid: report of 2 cases and review of the literature

BACKGROUND

Neuroendocrine tumors of the thyroid encompass a wide differential diagnosis. The most common is medullary thyroid carcinoma. One must consider other possibilities when a neuroendocrine thyroid tumor is calcitonin negative. We report 2 cases of Ewing sarcoma of the thyroid and discuss the differential diagnosis and workup of a calcitonin-negative neuroendocrine tumor of the thyroid.

METHODS/RESULTS

This is a retrospective review of 2 patients diagnosed with Ewing sarcoma of the thyroid and a review of the literature.

CONCLUSIONS

Ewing sarcoma of the thyroid is an exceedingly rare diagnosis, but should be included in the differential diagnosis for a thyroidal neuroendocrine lesion (especially in the absence of calcitonin). The use and interpretation of immunohistochemistry (IHC) and fluorescent in situ hybridization are essential in making the correct diagnosis.

Association of molecular alterations, including BRAF, with biology and outcome in pilocytic astrocytomas

Pilocytic astrocytoma (PA) is the most common glioma in the pediatric population. PAs can exhibit variable behavior that does not always correlate with location. Although oncogenic rearrangements of the BRAF gene have recently been described in PAs, it is not clear whether such alterations have an impact on outcome. An institutional cohort of 147 PAs (118 with outcome data) from both cerebellar and non-cerebellar locations (spine, diencephalon, midbrain, brainstem, and cortex) was utilized in this study. Parameters included quantification of characteristic morphologic variables as well as genes and molecular loci previously shown to be of relevance in high-grade gliomas, including 1p, 9p, 10q, 17p, 19q, and BRAF. Neither 1p, 9p, and 10q nor 19q showed significant association with outcome in PAs, although p16 deletion was more common in PAs of the midbrain, brainstem, and spinal cord. Loss of heterozygosity on 17p13 correlated with increased risk of recurrence in cerebellar tumors. BRAF gene rearrangements were more common in cerebellar tumors than non-cerebellar tumors and associated with classic biphasic histology in the cerebellum. However, clinical outcome was independent of BRAF status. The molecular biology of PAs differs according to location, yet BRAF rearrangements do not appear to produce PAs with different behavior. Nevertheless, such tumors may have altered sensitivity to pathway-specific adjuvant therapy. Additionally, deletion on 17p13 may be an adverse prognostic biomarker in cerebellar tumors.

A novel complex BRAF mutation detected in a solid variant of papillary thyroid carcinoma

BRAF gene mutations are identified in about 45% of papillary thyroid carcinomas (PTC) and represent the most common genetic event in this tumor. Here, we report a case of PTC, solid variant, with a complex BRAF mutation that involves one nucleotide substitution, C1796T, and a CTT triplet insertion, 1798_1799insCTT, located on the same allele. This mutation leads to the replacement of a threonine with an isoleucine, T599I, and replacement of a valine with an alanine and a leucine, V600delinsAL. This mutation was identified both in the preoperative fine needle aspirate sample and in the surgical specimen after total thyroidectomy. Other rare BRAF mutations in PTC are reviewed.

Pharmacodynamic Effect of Iopanoic Acid on Free T3 and T4 Levels in Amiodarone-induced Thyrotoxicosis

We describe the effects of iopanoic acid on daily levels of free triiodothyronine (FT3) and free thyroxine (FT4) in a patient with progressive type II amiodarone-induced thyrotoxicosis (AIT) who was undergoing thyroidectomy. The patient was a 59-year-old man who was undergoing amiodarone therapy while awaiting cardiac transplantation; the use of beta blockers and corticosteroids to control the AIT was contraindicated in this patient. Prior to thyroidectomy, the patient was started on iopanoic acid at 1.0 g twice a day; in response to gastrointestinal side effects, the dosage was subsequently reduced to 0.5 g twice a day. The patient responded to iopanoic acid with a rapid decrease in his FT3 level and slight increase in his FT4 level. This control of thyrotoxicosis allowed for an uneventful thyroidectomy, which was later followed by successful cardiac transplantation. Based on our findings in this single case, we believe that iopanoic can be used to rapidly lower FT3 levels and to treat symptoms of thyrotoxicosis in a preoperative setting. We also discuss the different pharmacodynamic effects that iopanoic acid has on FT3 and FT4 levels.

Pharmacodynamic effect of iopanoic acid on free T(3) and T(4) levels in amiodarone-induced thyrotoxicosis

We describe the effects of iopanoic acid on daily levels of free triiodothyronine (FT(3)) and free thyroxine (FT(4)) in a patient with progressive type II amiodarone-induced thyrotoxicosis (AIT) who was undergoing thyroidectomy. The patient was a 59-year-old man who was undergoing amiodarone therapy while awaiting cardiac transplantation; the use of beta blockers and corticosteroids to control the AIT was contraindicated in this patient. Prior to thyroidectomy, the patient was started on iopanoic acid at 1.0 g twice a day; in response to gastrointestinal side effects, the dosage was subsequently reduced to 0.5 g twice a day. The patient responded to iopanoic acid with a rapid decrease in his FT(3) level and slight increase in his FT(4) level. This control of thyrotoxicosis allowed for an uneventful thyroidectomy, which was later followed by successful cardiac transplantation. Based on our findings in this single case, we believe that iopanoic can be used to rapidly lower FT(3) levels and to treat symptoms of thyrotoxicosis in a preoperative setting. We also discuss the different pharmacodynamic effects that iopanoic acid has on FT(3) and FT(4) levels.

Adequacy of surgeon-performed ultrasound-guided thyroid fine-needle aspiration biopsy

OBJECTIVE

To determine the diagnostic accuracy of specimens obtained by a surgeon performing office-based ultrasound (US)-guided fine-needle aspiration biopsy (FNAB) of thyroid nodules.

SUBJECTS AND METHODS

From 2003 to 2006, a single surgeon performed 447 consecutive office-based US-guided FNABs without on-site cytological specimen evaluation. Adequate specimens had at least six clusters of follicular cells from at least two separate needle passes.

RESULTS

Non-diagnostic specimens occurred in 16 of 447 (3.6%) nodules, whereas suboptimal specimens occurred in 17 of 447 (3.8%). Adequate samples were obtained in 413 of 447 (92.6%) of specimens. Malignancy was present in 20 of 447 (4.5%) and atypical features were present in 37 of 447 (8.3%). Benign diagnoses were rendered in 357 of 447 (79.9%) of specimens, of which four of 357 (1.1%) represented false-negative results.

CONCLUSION

Prior publications recommend that obtaining adequate thyroid cytology specimens requires use of US-guided FNAB and on-site evaluation of cytology adequacy. This study demonstrates that a combination of experienced US guidance, both capillary and aspiration sampling, and three to four needle passes produce comparable results while conserving costs and resources.

Identification of a novel point mutation in the RET gene (Ala883Thr), which is associated with medullary thyroid carcinoma phenotype only in homozygous condition

The RET protooncogene mutations responsible for multiple endocrine neoplasia type 2 are inherited as autosomic dominant traits. We describe here a novel germline homozygous mutation in exon 15 of the RET gene that determines an amino acid substitution (Ala->Thr) at codon 883. The index case was a 51-yr-old patient with an apparently sporadic form of medullary thyroid cancer (MTC). RET gene mutations screening was performed in exons 10, 11, 13, 14, 15, and 16 by automatic sequence analysis. An unexpected homozygous GCT->ACT point mutation was found at codon 883 in exon 15 and confirmed by restriction analysis (Alu I). The presence of the two chromosomes 10 was confirmed by fluorescence in situ hybridization analysis on lymphocytes. As expected on the basis of the homozygosity of the index case, the parents were consanguineous (second-degree cousins). Eight relatives were further investigated: the mother, two sisters, and the son were positive for heterozygous RET mutation. The mother (82 yr old) showed a nodular goiter but was negative both for basal and pentagastrin stimulated calcitonin. The young son (15 yr old) and the two sisters (63 and 58 yr old) did not show any clinical and/or biochemical sign of MTC. One brother (59 yr old) was negative both for RET mutation and clinical/biochemical examination. The other brother, 56 yr of age, was positive for both homozygous RET mutation and serum calcitonin. When operated, the histological examination of the thyroid showed the presence of MTC and C cell hyperplasia. In conclusion, we identified a new germline RET gene mutation during a routine RET gene screening of an apparently sporadic MTC case. This mutation showed a very low transforming activity as demonstrated by the absence of MTC phenotype in heterozygous subjects. The possibility that the homozygous gene carriers were indeed carrying a germline loss of heterozygosity was excluded by fluorescence in situ hybridization analysis for RET gene performed on lymphocytes derived from one homozygous patient. The analysis of several RET polymorphisms also confirmed the presence of two mutated alleles in MTC affected patients and both mutated and wild-type allele in heterozygous subjects.

Targeted overexpression of IGF-I evokes distinct patterns of organ remodeling in smooth muscle cell tissue beds of transgenic mice

Smooth muscle cells (SMC) of the vascular wall, bladder, myometrium, and gastrointestinal and respiratory tracts retain the ability to proliferate postnatally, which enables adaptive responses to injury, hormonal, or mechanical stimulation. SMC growth is regulated by a number of mesenchymal growth factors, including insulin-like growth factor I (IGF-I). To explore the function of IGF-I on SMC in vivo, the mouse SMC alpha-actin promoter fragment SMP8 (-1074 bp, 63 bp of 5'UT and 2.5 kb of intron 1) was cloned upstream of rat IGF-I cDNA, and the fusion gene microinjected to fertilized eggs of the FVB-N mouse strain. Mating of hemizygous mice with controls produced about 50% transgenic offspring, with equal sex distribution. Transgenic IGF-I mRNA expression was confined to SMC-containing tissues, with the following hierarchy: bladder > stomach > aorta = uterus > intestine. There was no transgene expression in skeletal muscle, heart, or liver. Radioimmunoassayable IGF-I content was increased by 3.5- to 4-fold in aorta, and by almost 10-fold in bladder of transgenic mice at 5 and 10 wk, with no change in plasma IGF-I levels. Wet weight of bladder, stomach, intestine, uterus, and aorta was selectively increased, with no change in total body or carcass weight of transgenic animals. In situ hybridization showed that transgene expression was exquisitely targeted to the smooth muscle layers of the arteries, veins, bladder, ureter, stomach, intestine, and uterus. Paracrine overproduction of IGF-I resulted in hyperplasia of the muscular layers of these tissues, manifesting in remarkably different phenotypes in the various SMC beds. Whereas the muscular layer of the bladder and stomach exhibited a concentric thickening, the SMC of the intestine and uterus grew in a longitudinal fashion, resulting in a marked lengthening of the small bowel and of the uterine horns. This report describes the first successful targeting of expression of any functional protein capable of modifying the phenotype of SMC in transgenic mice. IGF-I stimulates SMC hyperplasia, leading to distinct patterns of organ remodeling in the different tissue environments.

Thyroid lesions in children and adolescents after the Chernobyl disaster: implications for the study of radiation tumorigenesis

Eight years after the Chernobyl nuclear accident, the most obvious effect is manifested by an increase in the prevalence of thyroid gland diseases in the exposed children and adolescents. In this study, we describe a comparative analysis of epidemiological, clinical, and morphological features of 92 malignant and 59 benign thyroid lesions from patients 5-18 yr of age exposed to radiation in Belarus as a result of the Chernobyl disaster. All of them were operated at the same institution during the period from September 1991 through December 1992. The highest number of patients that subsequently developed thyroid carcinomas was in the group that was less that 1 yr of age at the time of Chernobyl, and this number decreased progressively through age 12 yr. Conversely, none of the patients with benign lesions only was less than 2 yr old at the time of the accident, and an exposure age of 5-6 yr was a threshold separating significant prevalence of malignant tumors in younger children from the more frequent benign lesions in older patients (P < 0.001). Fifty-two percent of children with carcinomas and only 24% with benign lesions (P < 0.005) were residents of the Gomel region, which is the most contaminated in Belarus. The morphology of thyroid tissue adjacent to carcinomas showed a high prevalence of multinodular and diffuse changes, but not of adenomas or solitary adenomatoid nodules. There was a high prevalence of focal micropapillary hyperplasia with graded degrees of severity, which we hypothesize may correspond to precursors for papillary thyroid carcinoma in post-Chernobyl radiation-associated tumors.

Pediatric thyroid cancer after the Chernobyl disaster. Pathomorphologic study of 84 cases (1991-1992) from the Republic of Belarus

BACKGROUND

During the initial period after the Chernobyl accident, large amounts of radioactive iodine were released in fallout, resulting in serious exposure to the thyroid gland in the residents of areas around the nuclear power station. Beginning in 1990, a definite increase in the incidence of thyroid cancer was noted in children of the Republic of Belarus.

METHODS

Morphologic and clinical features of 84 cases of post-Chernobyl thyroid carcinoma in Belarussian children from 5 to 14 years of age are reported. The latent period for tumor development was 4-6 years, with a mean of 5.8 years.

RESULTS

Papillary carcinoma was found in 83 patients and medullary carcinoma in one. Besides typical papillary carcinoma (14%), solid (34%), follicular (33%), mixed (10%), and diffuse sclerosing (9%) variants were observed. The follow-up period ranged from 8 months to 2.5 years. One patient died, local recurrence developed in 2, and cervical lymph node metastases developed in 10. To date, the incidence of local recurrence or metastatic disease after surgery was significantly higher in patients 5-8 years of age and in residents of areas nearest to the Chernobyl station.

CONCLUSIONS

Post-Chernobyl pediatric thyroid carcinoma is characterized by a short latency, a higher proportion of tumors arising in young children, and an almost equal sex ratio. Microscopically, these tumors were usually aggressive, often demonstrating intraglandular tumor dissemination (92%), thyroid capsular and adjacent soft tissue invasion (89%), and cervical lymph node metastases (88%). Papillary carcinoma was diagnosed in 99% of cases, with an unusually high frequency of solid growth patterns. Morphologic changes in nonneoplastic thyroid tissue were present in 90% of the glands, and the most specific findings were vascular changes and perifollicular fibrosis.