Ozgur Mete

Immunohistochemical Biomarkers in Thyroid Pathology

The application of immunohistochemistry to the diagnosis of thyroid lesions has increased as new biomarkers have emerged. In this review, we discuss the biomarkers that are critical for accurate diagnosis, prognosis, and management. Immunohistochemical markers are used to confirm that an unusual tumor in the thyroid is indeed of thyroid origin, either of follicular epithelial or C-cell differentiation; the various mimics include nonthyroidal lesions such as parathyroid tumors, paragangliomas, thymic neoplasms, and metastatic malignancies. Tumors of thyroid follicular epithelial cells can be further subclassified using a number of immunohistochemical biomarkers that can distinguish follicular-derived from C-cell lesions and others that support malignancy in borderline cases. The use of mutation-specific antibodies can distinguish papillary carcinomas harboring a BRAFV600E mutation from RAS-like neoplasms. Immunostains have been developed to further identify molecular alterations underlying tumor development, including some rearrangements. Altered expression of several biomarkers that are known to be epigenetically modified in thyroid cancer can be used to assist in predicting more aggressive behavior such as a propensity to develop locoregional lymphatic spread. Immunohistochemistry can assist in identifying lymphatic and vascular invasion. Biomarkers can be applied to determine dedifferentiation and to further classify poorly differentiated and anaplastic carcinomas. The rare tumors associated with genetic predisposition to endocrine neoplasia can also be identified using some immunohistochemical stains. The application of these ancillary tools allows more accurate diagnosis and better understanding of pathogenesis while improving prediction and prognosis for patients with thyroid neoplasms.

Epidemiology and biomarker profile of pituitary adenohypophysial tumors

Recent studies have reported the prevalence of pituitary tumors to be ~1/1000 population. Many are prolactin-producing tumors that are managed medically, however, the epidemiology of surgically resected pituitary adenohypophysial neuroendocrine tumors has not been reported in a large series with detailed characterization. We reviewed 1055 adenohypophysial tumors from 1169 transsphenoidal resections from the pathology files of University Health Network, Toronto, 2001-2016. Tumors were characterized by immunohistochemical localization of transcription factors (Pit-1, ERα, SF-1, Tpit), hormones (adrenocorticotropin, growth hormone, prolactin, β-thyrotropin, β-folliculotropin, β-luteotropin, α-subunit), and other biomarkers (keratins, Ki67, p27, FGFR4). Electron microscopy was used only for unusual lesions. In this cohort, 51.3% of patients were female; the average age was 51 years. Gonadotroph tumors represented 42.5%. Pit-1-lineage-tumors represented 29.9%; these were subclassified as growth-hormone-predominant (somatotroph/mammosomatotroph/mixed; 53%), prolactin-predominant (lactotroph/acidophil-stem-cell; 28%), thyrotrophs (2%), plurihormonal (14%), and not-otherwise-specified (3%). Corticotroph tumors represented 17.1%. Only 4.5% were null cell tumors and 0.5% were unusual plurihormonal tumors. In 5.5% the tumor was not characterized for technical reasons (sample size, fixation, necrosis or other artifact). All corticotroph and plurihormonal tumors were positive for keratins; others tumors showed variable negativity with highest rates in gonadotroph (37.1%) and null cell tumors (28.2%). Tumors with a Ki67u2009≥u20093% comprised 60% of this cohort. Global loss of p27 was most frequent in corticotroph neoplasms, specifically those associated with elevated glucocorticoid levels. Corticotroph and lactotroph tumors were more common among females; gonadotroph tumors were more common among males. Younger patients had mainly corticotroph and Pit-1-lineage neoplasms, whereas older patients harbored mainly gonadotroph tumors. This represents one of the largest surgical series of morphologically characterized pituitary tumors reported to date and the first to include the routine use of transcription factors for tumor classification. The data provide the basis for clinicopathologic correlations that are helpful for prognostic and predictive patient management.

DICER1 Mutations Are Frequent in Adolescent-Onset Papillary Thyroid Carcinoma

ContextnPapillary thyroid carcinoma (PTC) is a common malignancy in adolescence and is molecularly and clinically distinct from adult PTC. Mutations in the DICER1 gene are associated with thyroid abnormalities, including multinodular goiter and differentiated thyroid carcinoma.nnnObjectivenIn this study, we sought to characterize the prevalence of DICER1 variants in pediatric PTC, specifically in tumors without conventional PTC oncogenic alterations.nnnPatientsnPatients (N = 40) who underwent partial or total thyroidectomy and who were <18 years of age at the time of surgery were selected.nnnDesignnThe 40 consecutive thyroidectomy specimens (30 malignant, 10 benign) underwent genotyping for 17 PTC-associated variants, as well as full sequencing of the exons and exon-intron boundaries of DICER1.nnnResultsnConventional alterations were found in 12 of 30 (40%) PTCs (five BRAFV600E, three RET/PTC1, four RET/PTC3). Pathogenic DICER1 variants were identified in 3 of 30 (10%) PTCs and in 2 of 10 (20%) benign nodules, all of which lacked conventional alterations and did not recur during follow-up. DICER1 alterations thus constituted 3 of 18 (16.7%) PTCs without conventional alterations. The three DICER1-mutated carcinomas each had two somatic DICER1 alterations, whereas two follicular-nodular lesions arose in those with germline DICER1 mutations and harbored characteristic second somatic RNase IIIb hotspot mutations.nnnConclusionsnDICER1 is a driver of pediatric thyroid nodules, and DICER1-mutated PTC may represent a distinct class of low-risk malignancies. Given the prevalence of variants in children, we advocate for inclusion of DICER1 sequencing and gene dosage determination in molecular analysis of pediatric thyroid specimens.

Immunohistochemical Biomarkers in Pituitary Pathology

Pituitary pathology is one area of endocrine pathology that is highly dependent on immunohistochemistry. There is a wide range of disorders that occur in and around the sella turcica, and the distinction of tumor-like lesions from neoplasms requires careful evaluation. The diagnosis, prognosis, and predictive features of neoplasms in the sellar region are all dependent on the application and interpretation of biomarkers of cell differentiation, hormonal activity, subcellular morphology, and proliferation. As in hematopathology, the number of biomarkers has increased dramatically and continues to increase. Fortunately, some of the biomarkers provide information that was initially dependent on electron microscopy; therefore, the need for this additional technology has been reduced to only rare unusual tumors. In this review, we provide a simple approach to understanding the importance of the various biomarkers that are used to ensure the correct diagnosis and provide the treating clinicians with tools to guide appropriate patient management and surveillance.

Immunohistochemical Biomarkers of Adrenal Cortical Neoplasms

Careful morphological evaluation forms the basis of the workup of an adrenal cortical neoplasm. However, the adoption of immunohistochemical biomarkers has added tremendous value to enhance diagnostic accuracy. The authors provide a brief review of immunohistochemical biomarkers that have been used in the confirmation of adrenal cortical origin and in the detection of the source of functional adrenal cortical proliferations, as well as diagnostic, predictive, and prognostic biomarkers of adrenal cortical carcinoma. In addition, a brief section on potential novel theranostic biomarkers in the prediction of treatment response to mitotane and other relevant chemotherapeutic agents is also provided. In the era of precision and personalized medical practice, adoption of combined morphology and immunohistochemistry provides a new approach to the diagnostic workup of adrenal cortical neoplasms, reflecting the evolution of clinical responsibility of pathologists.

The Many Faces of Primary Aldosteronism and Cushing Syndrome: A Reflection of Adrenocortical Tumor Heterogeneity

Adrenal cortical tumors constitute a heterogeneous group of neoplasms with distinct clinical, morphological, and molecular features. Recent discoveries of specific genotype–phenotype correlations in adrenal cortical adenomas have transformed our understanding of their respective endocrine syndromes. Indeed, a proportion of patients with primary aldosteronism are now known to harbor adrenal cortical adenomas with heterogeneous molecular alterations (KCNJ5, ATP1A1, ATP2B3, and CACNA1D) involving the calcium/calmodulin kinase signaling pathway. Several lines of evidence suggest that KCNJ5-mutant aldosterone-producing adenomas have distinct clinicopathological phenotype compared to those harboring ATP1A1, ATP2B3, and CACNA1D mutations. Benign adrenal cortical tumors presenting with Cushing syndrome often have diverse mutations (PRKACA, PRKAR1A, GNAS, PDE11A, and PDE8B) involving the cyclic AMP signaling pathway. In addition to cortisol-producing adenomas, bilateral micronodular adrenocortical disease and primary bilateral macronodular adrenal hyperplasia (PBMAH) have also expanded the spectrum of benign neoplasms causing adrenal Cushing disease. The recent discovery of inactivating ARMC5 germline mutations in PBMAH has challenged the old belief that this disorder is mainly a sporadic disease. Emerging evidence suggests that PBMAH harbors multiple distinct clonal proliferations, reflecting the heterogeneous genomic landscape of this disease. Although most solitary adrenal cortical tumors are sporadic, there is an increasing recognition that inherited susceptibility syndromes may also play a role in their pathogenesis. This review highlights the molecular and morphological heterogeneity of benign adrenal cortical neoplasms, reflected in the diverse presentations of primary aldosteronism and adrenal Cushing syndrome.

Immunohistochemistry in Diagnostic Parathyroid Pathology

Pathologists are usually readily able to diagnose parathyroid tissues and diseases, particularly when they have knowledge of the clinical information, laboratory findings, and radiographic imaging studies. However, the identification of parathyroid tissue or lesions can be difficult in small biopsies, ectopic locations, supranumerary glands, and in some oxyphil/oncocytic lesions. Widely available immunohistochemical studies such as chromogranin-A, synaptophysin, keratin, parathyroid hormone, thyroglobulin, and thyroid transcription factor-1 can help in difficult cases. One of the most difficult diagnostic aspects faced by the pathologist in evaluating parathyroid is distinguishing between parathyroid adenoma, particularly atypical adenoma, and parathyroid carcinoma. Many markers have and continue to be evaluated for diagnostic utility, and are even beginning to be studied for prognostic utility. Single immunohistochemical markers such as parafibromin and Ki-67 are among the most studied and most utilized, but many additional markers have and continue to be evaluated such as galectin-3, PGP9.5, Rb, bcl2, p27, hTERT, mdm2, and APC. Although not widely available in many laboratories, a panel of immunohistochemical markers may prove most useful as an adjunct in the evaluation of challenging parathyroid tumors.

Noninvasive Follicular Thyroid Neoplasm with Papillary-Like Nuclear Features (NIFTP): Trading Six for a Risky Half Dozen: Reply

Since the term noninvasive follicular neoplasm with papillary-like nuclear features (NIFTP) was introduced, its existence has been controversial. The resultant debate has left clinicians confused as to how to counsel and follow their patients diagnosed with this entity. The authors would like to thank Dr. Rosàrio for his support with respect to our recent article on the clinical safety of renaming encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC) [1]. The authors believe that a continued academic discourse as well as further research on the topic is necessary to clarify the ongoing uncertainty. After Nikiforov et al. [2] published their article suggesting that the nomenclature for the low-risk thyroid cancer variant EFVPTC be changed to NIFTP, the authors found that the experience at the University Health Network was significantly different with respect to both incidence and malignant potential [1]. In addition to Parente et al., there have been several studies indicating that EFVPTC has both malignant potential and a low incidence [1, 3, 4]. The authors certainly support the de-escalation of treatment of these low-risk thyroid cancers including the use of thyroid lobectomy and more selective radioactive iodine ablation. However, the avoidance of the term ‘‘cancer’’ for an entity with malignant potential may result in undertreatment or inappropriate lack of surveillance of patients with these tumors. In this regard, change in terminology is not a substitute for meaningful patient education and multidisciplinary discussion to highlight the low-risk nature of these cancers. Until future research can clarify the current controversy in the literature, clinicians should continue to follow and counsel patients about this low-risk malignant entity. Furthermore, ongoing capture of this diagnostic category by Cancer Registries is essential for both quality improvement and investigational study.

The Diagnosis and Clinical Significance of Paragangliomas in Unusual Locations

Paragangliomas are neuroendocrine neoplasms, derived from paraganglia of the sympathetic and parasympathetic nervous systems. They are most commonly identified in the head and neck, being most frequent in the carotid body, followed by jugulotympanic paraganglia, vagal nerve and ganglion nodosum, as well as laryngeal paraganglia. Abdominal sites include the well-known urinary bladder tumors that originate in the Organ of Zuckerkandl. However, other unusual sites of origin include peri-adrenal, para-aortic, inter-aortocaval, and paracaval retroperitoneal sites, as well as tumors in organs where they may not be expected in the differential diagnosis of neuroendocrine neoplasms, such as thyroid, parathyroid, pituitary, gut, pancreas, liver, mesentery, lung, heart and mediastinum. The distinction of these lesions from epithelial neuroendocrine neoplasms is critical for several reasons. Firstly, the determination of clinical and biochemical features is different from that used for epithelial neuroendocrine tumors. Secondly, the genetic implications are different, since paragangliomas/pheochromocytomas have the highest rate of germline susceptibility at almost 40%. Finally, the characterization of metastatic disease is unique in these highly syndromic lesions. In this review, we summarize updated concepts by outlining the spectrum of anatomic locations of paragangliomas, the importance of morphology in establishing the correct diagnosis, the clinical implications for management, and the impact of genetics on the distinction between multifocal primary tumors compared with malignant disease.

Synchronous Multiple Pituitary Neuroendocrine Tumors of Different Cell Lineages

We report clinicopathological features of a large series of synchronous multiple pituitary neuroendocrine tumors (PitNETs) of different cell lineages. Retrospective review of pathology records from 2001 to 2016 identified 13 synchronous multiple PitNETs from 1055 PitNETs classified using pituitary cell-lineage transcription factors, adenohypohyseal hormones, and other biomarkers. Clinical, radiological, and histopathological features of these tumors were reviewed. The series included seven females and six males. Mean age at diagnosis was 55.23xa0years (range 36–73). Imaging was unavailable for four patients; among the other nine, mean tumor size was 2.23xa0cm (range 0.9–3.9). Five patients had acromegaly, four had Cushing disease, and four had clinically non-functional tumors. Twelve had double PitNETs; one had a triple PitNET. The most common tumor type was corticotroph (nxa0=u20098; six densely and one sparsely granulated and one Crooke cell; three densely and one sparsely granulated were clinically silent), gonadotroph tumors (nu2009=u20098), and somatotroph tumors (nxa0=u20095; four sparsely granulated and one densely granulated somatotroph) were followed by lactotroph tumors (nxa0=u20094; all sparsely granulated), poorly differentiated Pit-1 lineage tumor (nxa0=u20091), and unusual plurihormonal tumor (nu2009=u20091). A 54-year-old man with Cushing disease had MEN1-driven Crooke cell and gonadotroph tumors. The triple pitNET consisted of a multilineage plurihormonal tumor associated with a gonadotroph and a sparsely granulated lactotroph tumor. The Ki67 (available from 10 specimens) ranged from 1 to 5% in individual tumors. Radiological and biochemical follow-up was available for 10 and 11 patients, respectively. Radiological tumor persistence/recurrence was identified in three patients with double PitNETs consisting of sparsely granulated lactotroph and gonadotroph tumors (nxa0=u20091), sparsely granulated somatotroph and silent corticotroph tumors (nu2009=u20091), and gonadotroph and silent corticotroph tumors (nu2009=u20091) with cavernous sinus invasion. Biochemical persistence was noted in four patients with double PitNETs consisting of sparsely granulated somatotroph and silent corticotroph tumors (nxa0=u20092), gonadotroph and Crooke cell tumors (nxa0=u20091), and densely granulated somatotroph and silent corticotroph tumors (nu2009=u20091). Multiple PitNETs represent about 1% of PitNETs and usually have hormone excess due to at least one tumor component. Clinical manifestations may be due to the minor component, especially in patients with Cushing disease. Invasive growth and aggressive histological subtypes predicted disease persistence/recurrence. This series also highlights the importance of routine application of pituitary cell lineage transcription factors along with hormones to distinguish and subtype multiple synchronous PitNETs.