TERT Promoter Mutation Spatial Heterogeneity in a Metastatic Follicular Thyroid Carcinoma: Implications for Clinical Work-Up Abstract Follicular thyroid carcinoma (FTC) is not routinely diagnosed by a preoperative fine needle aspiration biopsy (FNAB), and the final diagnosis relies on histopathological criteria visible upon microscopic examination of the excised tumor. Several markers have been proposed as helpful in the identification of follicular thyroid tumors with malignant potential and worse prognosis, of which the specific point mutations C250T and C228T in the Telomerase Reverse Transcriptase (TERT) promoter region seem to be particularly promising. We describe a patient presenting with a large pelvic mass, in which a core needle biopsy was consistent with follicular-patterned thyroid tissue positive for a Q61R NRAS mutation and the C228T TERT promoter mutation. Upon clinical investigation, a 60-mm lesion was detected in the right thyroid lobe. The ensuing FNAB was consistent with a follicular thyroid tumor, Bethesda IV, positive for the same NRAS mutation and both the C228T and C250T TERT promoter mutations. A total thyroidectomy was performed, and a widely invasive FTC was diagnosed. Tumor tissue samples from various parts of the primary lesion were investigated for TERT promoter mutations, displaying C228T in three samples and C250T in one. Interestingly, the C228T mutations showed a coupling to areas with high Ki-67 proliferation indexes. Our data indicate that TERT promoter mutations can exhibit spatial heterogeneity in FTCs, with implications for clinical management as well as providing insights into the molecular biology underlying the tumoral etiology.

The Utility of Intraoperative Cytological Smear and Frozen Section in the Surgical Management of Patients with Cushing’s Disease due to Pituitary Microadenomas Abstract Cushing’s disease (CD) is most commonly caused by a microadenoma, which at surgical exploration may not provide adequate tissue for pathologic diagnosis using standard techniques. We wished to determine the accuracy of intraoperative pathologic examination and whether the addition of intraoperative cytology increased the diagnostic yield. We reviewed the pathology reports from 403 operations on 341 patients with CD microadenomas from a single institution. The concordance rates of intraoperative diagnoses (cytology and frozen) with the final (paraffin section) pathological diagnosis were calculated. The overall pathologic confirmation of an adenoma (by either cytology, frozen, or paraffin section) was compared with the result from a historical cohort (using only standard frozen section analysis but not intraoperative cytology) and the pooled result from a meta-analysis of previously published data. The concordance rate between frozen section diagnosis and paraffin section histology was 390/403 (96.8%). The concordance rate between cytological smear and paraffin section histology was 213/246 (86.6%). In 54 cases (13.4%) with ultimate remission, pathologic confirmation was obtained only on intraoperative pathology (frozen section or cytology). Overall, pathologic confirmation was obtained in 326 operations (80.9%) by at least one pathological modality. The overall pathological confirmation of an adenoma was greater after the introduction of intraoperative cytology when compared with the historical control (67.1%, p = 0.015), and compared with the pooled rate of published data from the meta-analysis (72.1%, p < 0.001). Our findings suggest that addition of intraoperative cytological analyses during surgery for CD is an additional useful diagnostic tool for both neurosurgeons and pathologists.

Neuroendocrine Neoplasms Associated with Germline Pathogenic Variants in the Homologous Recombination Pathway Abstract Neuroendocrine neoplasms (NENs) have been primarily associated with germline pathogenic variants in genes involved in chromatin remodeling (MEN1), cell cycle control (CDKN1B), PI3K/mTOR signaling (TSC1/2, PTEN) as well as pseudohypoxia (VHL, SDHx). Recent work has implicated various genes involved in DNA repair pathways in the pathophysiology of a subset of pancreatic neuroendocrine neoplasms, including BRCA2, via the homologous recombination pathway (HRD). To date, germline variants in other HRD pathway genes have not been described to contribute to NEN. PALB2, RAD51C, and BARD1 are additional tumor suppressor genes which also mediate repair of double stranded DNA breaks through the HRD pathway and are implicated in hereditary breast (PALB2; BARD1) and ovarian (RAD51C) cancer. Here we report three cases of NEN associated with germline pathogenic variants in PALB2 (pancreatic NEN), RAD51C (thymic NEN), and BARD1 (pancreaticoduodenal NEN) respectively, further linking the DNA repair pathway to NENs.

A Systematic Review and Meta-Analysis of the Diagnostic Performance of BRAF V600E Immunohistochemistry in Thyroid Histopathology Abstract Immunohistochemistry (IHC) in evaluating thyroid surgical specimens may facilitate diagnostic and prognostic evaluation, with potential therapeutic implications. We performed a systematic review and meta-analysis examining the analytic validity of IHC in detecting BRAFV600E mutations in thyroid cancer (primary or metastatic). We screened citations from three electronic databases (until December 20, 2018), supplemented by a hand search of authors’ files and cross-references of reviews. Citations and full-text papers were independently reviewed in duplicate, and consensus was achieved on inclusion of papers. Two reviewers independently critically appraised and abstracted data from included papers. Random-effect meta-analyses were conducted for sensitivity and specificity estimates. We reviewed 1499 unique citations and 93 full-text articles. We included 1 systematic review and 30 original articles. The published review (from 2015) needed to be updated as there were multiple subsequent original studies. The pooled sensitivity of IHC in detecting a BRAFV600E mutation was 96.8% (95% confidence interval [CI] at 94.1%, 98.3%) (29 studies, including 2659 BRAFV600E mutant tumors). The IHC pooled specificity was 86.3% (95% CI 80.7%, 90.4%) (28 studies, including 1107 BRAFV600E wild-type specimens). These meta-analyses were subject to statistically significant heterogeneity, partly explained by antibody type (sensitivity and specificity) and tissue/tumor type (specificity). In conclusion, BRAF IHC is highly sensitive and reasonably specific in detecting the BRAFV600E mutation; however, there is some variability in analytic performance.

Systematic Review and Meta-analysis of the Impact of Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP) on Cytological Diagnosis and Thyroid Cancer Prevalence Abstract A re-named diagnosis of noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) likely impacts the prevalence of thyroid cancer and risk of malignancy in populations based on the established Bethesda System of Reporting Thyroid Cytopathology (TBSRTC). This study was done to investigate the prevalence and cytological distribution of NIFTP. PRISMA guided systematic review was done from a database search of Pubmed, EMBASE, and Medline using the search terms “non-invasive follicular thyroid neoplasm with papillary-like nuclear features”, “non-invasive follicular variant of papillary carcinoma”, “niftp”, and “Bethesda” until November 2018. Original articles with surgically proven diagnoses of NIFTP using strict NIFTP criteria were included. Twenty-nine studies with 1563 cases of NIFTP were included. The pooled prevalence of NIFTP in cases which would be classified previously as the follicular variant of papillary thyroid cancer (FVPTC) and papillary thyroid cancer (PTC) were 43.5% (95% CI 33.5–54.0%) and 4.4% (95% CI 2.0–9.0%) respectively. The pooled TBSRTC distribution of cases diagnosed as NIFTP was: from the non-diagnostic category 3.6% (95% CI 2.4–5.3%), benign 10.0% (95% CI 7.2–13.6%), AUS/FLUS 34.2% (95% CI 28.2–40.8%), FN/SFN 22.7% (95% CI 17.2–29.4%), suspicious for malignancy 22.4% (95% CI 17.7–27.9%), and malignant 7.5% (95% CI 4.2–12.9%). While a significant reduction in FVPTC prevalence is anticipated, a modest reduction of PTC prevalence is also expected with adoption of the NIFTP terminology that would be distributed mainly among lesions classified as indeterminate thyroid nodules. Further studies are needed to identify unique clinical characteristics of these lesions preoperatively.

Comprehensive Evaluation of Rare Pituitary Lesions: A Single Tertiary Care Pituitary Center Experience and Review of the Literature Abstract The 2017 World Health Organization classification of central nervous system and endocrine tumors have introduced significant changes in the diagnostic criteria for pituitary lesions. The aim of our paper is to describe the epidemiological, clinico-pathological, and radiological features of a single consecutive institutional surgical series of rare pituitary lesions, using these new criteria. Of the 316 endoscopic endonasal trans-sphenoidal approaches performed for pituitary lesions between 2010 and 2018, 15 rare lesions were encountered. These included metastases, pituitary carcinomas, pituicytomas, granular cell tumor, primary pituitary lymphomas, germinoma, mixed gangliocytoma–adenoma, hypophysitis, and pituitary hyperplasia. Their clinical, radiological, and pathological features are herewith presented along with a literature review that enabled us to propose an algorithm to facilitate a diagnosis for rare pituitary lesions.

Synaptic Vesicle Protein 2 and Vesicular Monoamine Transporter 1 and 2 Are Expressed in Neuroblastoma Abstract Neuroblastoma (NB), the most common extracranial cancer in childhood, exhibits neuroendocrine (NE) differentiation. Two well-established NE markers, chromogranin A (CgA) and synaptophysin (syn), are used in the histopathological diagnostics. Our aims were to explore if the NE markers synaptic vesicle protein 2 (SV2) and vesicular monoamine transporter 1 (VMAT1) and 2 (VMAT2) also are expressed in human NB and if so, evaluate their usefulness in NB histopathological diagnostics. Tumor specimens from 21 NB patients, before and/or after chemotherapy, were immunostained for CgA, syn, SV2, VMAT1, and VMAT2. Clinical data was extracted from patients’ records. SV2 was highly expressed in NB, as was CgA while syn was less frequently expressed compared to the other two. Both VMATs were expressed in several NB, VMAT2 in more cases than VMAT1 and its expression was similar to syn. Chemotherapy did not affect the immunoreactivity in an obvious way. SV2 was highly expressed in NB and can thus be useful marker in NB diagnostics. VMAT1 and VMAT2 were also expressed in NB but similar to syn less reliable as tumor markers.

Overexpression of Histone H3 Lysine 27 Trimethylation Is Associated with Aggressiveness and Dedifferentiation of Thyroid Cancer Abstract A variety of epigenetic dysregulations are observed in thyroid malignancies. EZH2, the catalytic subunit of polycomb repressive complex 2, is upregulated in advanced thyroid cancers. EZH2 can catalyze trimethylation of histone H3 at lysine 27 (H3K27me3) and contribute to transcriptional silencing of target genes. Here, we investigated the immunohistochemical expression of H3K27me3 in neoplastic and normal thyroid tissues. Normal thyroid epithelial cells typically exhibited nuclear staining of moderate intensity. A similar expression pattern was observed in nodular goiters and follicular adenomas. By contrast, strong H3K27me3 expression was evident in 80% (8/10) lymphocytic thyroiditis, 63% (80/127) papillary thyroid cancer, 41% (7/17) follicular thyroid cancer, and 73% (8/11) poorly differentiated and anaplastic thyroid cancer. In differentiated thyroid cancer, strong H3K27me3 expression was associated with extrathyroidal extension (p < 0.001), lymphovascular invasion (p = 0.029), lymph node metastasis (p = 0.006), and higher risk of recurrence (p = 0.003). Our results indicate that H3K27me3 overexpression may be implicated in aggressiveness and dedifferentiation of thyroid cancer. In addition to prognostication, the predictive value of H3K27me3 expression deserves further investigation given the recent development of epigenetic targeting agents.

Diagnostic Pitfall: Parathyroid Carcinoma Expands the Spectrum of Calcitonin and Calcitonin Gene-Related Peptide Expressing Neuroendocrine Neoplasms

Negative Results on Thyroid Molecular Testing Decrease Rates of Surgery for Indeterminate Thyroid Nodules Abstract Molecular tests and mutational panels such as Afirma Gene Expression Classifier (GEC) and ThyroSeq, respectively, have been used to help risk stratify cytologically indeterminate thyroid nodules with the aim to reduce unnecessary surgeries. We studied the effect of molecular testing on the rate of surgical resection in these nodules. Thyroid nodules with indeterminate (Bethesda III/IV) cytology that underwent molecular testing (GEC or ThyroSeq) at our institution between June 2012 and August 2016 were retrospectively reviewed. We collected demographics, cytology diagnoses, molecular test results, and whether surgical resection was performed. Two hundred eighty-three nodules met inclusion criteria: 202 nodules tested with GEC and 81 tested with ThyroSeq. In the cohort of GEC-tested nodules, 99/202 (49%) yielded “suspicious” and 103/202 (51%) yielded “benign” results, with an overall resection rate of 70/99 (71%) in “suspicious” versus 13/103 (13%) in “benign” nodules. In the cohort of ThyroSeq-tested nodules, 13/81 (16%) of nodules yielded a “high-risk mutation” and 68/81 (84%) of nodules yielded “no high-risk mutation,” with overall resection rates of 11/13 (85%) and 30/68 (44%), respectively. Rates of resection were higher for Bethesda IV than for III nodules, regardless of molecular results. For both GEC and ThyroSeq, molecular test results seemed to correlate with the rate of resection at our institution. Rates of resection for cytologically indeterminate nodules that were “benign” or “no high-risk mutation” appeared to differ from those that were “suspicious” or “high-risk mutation” on molecular panel testing by GEC and ThyroSeq, respectively. Our findings support that molecular test results are impacting management.