Molecular Profiling of 50 734 Bethesda III-VI Thyroid Nodules by ThyroSeq v3: Implications for Personalized Management

CONTEXT

Comprehensive genomic analysis of thyroid nodules for multiple classes of molecular alterations detected in a large series of fine needle aspiration (FNA) samples has not been reported.

OBJECTIVE

To determine the prevalence of clinically relevant molecular alterations in Bethesda categories III-VI (BCIII-VI) thyroid nodules.

METHODS

This retrospective analysis of FNA samples, tested by ThyroSeq v3 using Genomic Classifier and Cancer Risk Classifier at UPMC Molecular and Genomic Pathology laboratory, analyzed the prevalence of diagnostic, prognostic, and targetable genetic alterations in a total of 50 734 BCIII-VI nodules from 48 225 patients.

RESULTS

Among 50 734 informative FNA samples, 65.3% were test-negative, 33.9% positive, 0.2% positive for medullary carcinoma, and 0.6% positive for parathyroid. The benign call rate in BCIII-IV nodules was 68%. Among test-positive samples, 73.3% had mutations, 11.3% gene fusions, and 10.8% isolated copy number alterations. Comparing BCIII-IV nodules with BCV-VI nodules revealed a shift from predominantly RAS-like alterations to BRAF V600E-like alterations and fusions involving receptor tyrosine kinases (RTK). Using ThyroSeq Cancer Risk Classifier, a high-risk profile, which typically included TERT or TP53 mutations, was found in 6% of samples, more frequently BCV-VI. RNA-Seq confirmed ThyroSeq detection of novel RTK fusions in 98.9% of cases.

CONCLUSION

In this series, 68% of BCIII-IV nodules were classified as negative by ThyroSeq, potentially preventing diagnostic surgery in this subset of patients. Specific genetic alterations were detected in most BCV-VI nodules, with a higher prevalence of BRAF and TERT mutations and targetable gene fusions compared to BCIII-IV nodules, offering prognostic and therapeutic information for patient management.

ODP309 Ectopic Cushing's Syndrome: Importance of Methodical Approach to Hide and Seek

Cushing's syndrome (CS) is associated with high morbidity and fivefold excess mortality. Ectopic ACTH syndrome accounts for 20% of CS cases. It is crucial to identify and localize the source of extrapituitary ACTH secretion because surgical resection of the primary, often malignant, tumor has a high probability of cure with complete remission in 80% of cases. A 72-year-old female was admitted to a community hospital for lateral chest pain after a fall. She endorsed progressive weight gain, new HTN, emotional lability and worsening cognition over the prior 6 months. ACTH and cortisol levels were elevated. MRI brain failed to identify a pituitary lesion. CT chest showed multiple rib fractures and anterior mediastinal mass which was biopsied. While awaiting pathology results, IPS sampling attempted but aborted due to pulmonary edema necessitating ICU care. She was transferred to our institution for planned TSR of suspected pituitary adenoma. Examination showed Cushingoid features. Labs showed hypokalemia, high cortisol and high ACTH. MRI pituitary showed normal sella. MRI spine showed multilevel vertebral compression fractures. CT chest showed interval growth of mediastinal mass. A 1 mg dexamethasone suppression test failed to suppress ACTH and cortisol, confirming ACTH dependent hypercortisolism. A high dose 8 mg dexamethasone test failed to suppress ACTH and cortisol, a 10 mcg DDAVP stimulation test showed a flat response, with ACTH and cortisol levels remaining comparable before and after DDAVP injection. Dynamic testing therefore consistent with ectopic ACTH dependent hypercortisolism. Gallium-68 DOTA-TATE PET Scan demonstrated uptake in mediastinal mass suggestive of somatostatin receptor positive neuroendocrine tumor. Biopsy specimens processed at our institution showed cells positive for epithelial markers Cytokeratin and PAX8. Sample showed neuroendocrine differentiation with positive staining for Chromogranin A, synaptophysin and CD 117. Findings consistent with neuroendocrine thymic neoplasm. The patient was started on oral ketoconazole to control hypercortisolism. Surgical resection of tumor was planned with intent to cure CS. Ultimately, due to proximal myopathy and multiple vertebral fractures her performance status was too poor for safe tumor resection. Unfortunately, she died of complications related to CS while attempting preoperative rehabilitation. This case illustrates the importance of a timely, systematic evaluation for ACTH source in ACTH dependent hypercortisolism. Delay in CS diagnosis and localizing correct ACTH source led to missing the window of fitness for curative surgery. If ACTH is elevated, the most common source is pituitary neoplasia, however ectopic ACTH production must be ruled out. Dynamic testing including high dose dexamethasone suppression test, CRH and DDAVP stimulation tests should be used for preliminary localization of ACTH production. IPS sampling is invasive with greater potential for complications, as in the case of our patient. Therefore, it is only indicated if there are conflicting results from different dynamic tests and imaging studies.

Presentation: No date and time listed

Defects of Thyroid Hormone Synthesis and Action

Congenital hypothyroidism (CH) is the most common inborn endocrine disorder and causes significant morbidity. To date, we are only aware of the molecular basis responsible for the defects in a small portion of patients with CH. A better understanding of the pathophysiology of these cases at the genetic and molecular basis provides useful information for proper counseling to patients and their families a well as for the development of better targeted therapies. This article provides a succinct outline of the pathophysiology and genetics of the known causes of thyroid dysgenesis, dyshormonogenesis, and syndrome of impaired sensitivity to thyroid hormone.

New JAG1 Mutation Causing Alagille Syndrome Presenting With Severe Hypercholesterolemia: Case Report With Emphasis on Genetics and Lipid Abnormalities

CONTEXT

Alagille syndrome is a rare autosomal-dominant genetic disorder caused by defects in the Notch signaling pathway, which involves multiple organ systems. Bile duct paucity is the main characteristic feature of the disease, which often leads to cholestatic hypercholesterolemia.

CASE DESCRIPTION

We report the case of a male infant who had developed failure to thrive, jaundice, intermittent pruritus, and multiple diffuse symmetrical skin xanthomas at 1 year of age. He was diagnosed with pulmonary stenosis, butterfly vertebrae of T4, T6, and T8; horseshoe kidney, and embryotoxon in the left eye. Laboratory workup revealed severe hypercholesterolemia. Alagille syndrome was suspected and confirmed by genetic testing, which identified a previously undescribed frameshift pathogenic heterozygous variant in the JAG1 gene, p.Arg486Lysfs*5.

CONCLUSIONS

Here, we report a unique case of a patient diagnosed with Alagille syndrome who was found to have a previously undescribed frameshift pathogenic mutation in the JAG1 gene and who presented with xanthomatosis and levels of hypercholesterolemia more than 2 times higher than those previously reported in the literature. We also provide a review of the different pathophysiologic mechanisms associated with the increase in serum cholesterol and low-density lipoprotein cholesterol concentrations seen in cholestatic liver disease in general and in Alagille syndrome in particular.

Thyroid Hormone Replacement in Patients Following Thyroidectomy for Thyroid Cancer

Thyroid hormone replacement therapy in patients following thyroidectomy for thyroid cancer, although a potentially straightforward clinical problem, can present the clinician and patient with a variety of challenges. Most often the problems are related to the dose and preparation of thyroid hormone (TH) to use. Some patients feel less well following thyroidectomy and/or radioiodine ablation than they did before their diagnosis. We present evidence that levothyroxine (L-T4) is the preparation of choice, and keeping the thyroid-stimulating hormone (TSH) between detectable and 0.1 mU/L should be the standard of care in most cases. In unusual circumstances, when the patient remains clinically hypothyroid despite a suppressed TSH, we acknowledge there may be as yet unidentified factors influencing the body's response to TH, and individualized therapy may be necessary in such patients.

A Novel non-sense Mutation in Keratin 10 Causes a Familial Case of Recessive Epidermolytic Ichthyosis

Epidermolytic ichthyosis (EI) is a rare skin disorder characterized by generalized erythroderma and cutaneous blistering at birth, which is substituted by hyperkeratosis later in life. It is caused by autosomal dominant mutations in highly conserved regions of KRT1 and KRT10. To date, only four mutations with autosomal recessive inheritance of EI have been described in consanguineous families. All of them affect the 2B domain of KRT10. In the present study, we describe four patients with EI (including one lethal case) born from unaffected parents in a consanguineous family of a native Venezuelan community. The objective of this study was to characterize the clinical, genetic, and morphological aspects of the disease in this family, as well as understand its functional implications. Genomic DNA was sequenced for KRT10 and KRT1. Immunofluoresence for keratin expression was performed on cutaneous biopsies. After examination of cutaneous biopsies histology, our results showed hyperkeratosis and acantholysis with an expanded granular layer. Sequencing of KRT10 demonstrated a nonsense mutation (p.Tyr282Ter.) corresponding to the 1B domain of the protein in patients and a heterozygous pattern in other family members, resulting in complete absence of K10. The loss of K10 was compensated by upregulation of K14 and K17. In conclusion, this novel mutation in KRT10 is the first recessive genetic variation that is not located in the so called “hot spot” for recessive EI, suggesting that other areas of the gene are also susceptible for such mutations.