Hot Trends in Pheochromocytoma and Paraganglioma: Are We Getting Closer to Personalized Dynamic Prognostication?

Pheochromocytoma and abdominal paraganglioma (PPGL) are rare catecholamine-producing, keratin-negative, non-epithelial neuroendocrine neoplasms characterized by a unique association with syndromic diseases caused by constitutional mutations in a wide range of susceptibility genes. While PPGLs are recognized for their malignant potential, the risk of metastatic disease varies depending on several clinical, histological, and genetic factors. Accurate diagnosis and prognosis of these tumors require a multidisciplinary approach, integrating insights from various medical specialties. Pathologists play a crucial role in this complex task, as numerous morphological, immunohistochemical, and genetic findings can be linked to worse outcomes. Therefore, it is vital to stay informed about the latest advancements in PPGL pathology. This brief review provides an overview of the challenges associated with PPGLs and highlights the most recent developments in tumor prognostication.

Genetic variants and down-regulation of CACNA1H in pheochromocytoma.

Pheochromocytoma (PCC) and abdominal paraganglioma (aPGL) (together abbreviated PPGL) frequently present with an underlying genetic event in a PPGL driver gene, and additional susceptibility genes are anticipated. Here, we re-analyzed whole-exome sequencing data for PCC patients and identified two patients with rare missense variants in the calcium voltage-gated channel subunit 1H gene (CACNA1H). CACNA1H variants were also found in the clinical setting in PCC patients using targeted sequencing and from analysis of The Cancer Genome Atlas database. In total, CACNA1H variants were found in six PCC cases. Three of these were constitutional, and two are known to have functional consequences on hormone production and gene expression in primary aldosteronism and aldosterone-producing adrenocortical adenoma. In general, PPGL exhibited reduced CACNA1H mRNA expression as compared to normal adrenal. Immunohistochemistry showed strong CACNA1H (CaV3.2) staining in adrenal medulla while PPGL typically had weak or negative staining. Reduced CACNA1H gene expression was especially pronounced in PCC compared to aPGL and in PPGL with cluster 2 kinase signaling phenotype. Furthermore, CACNA1H levels correlated with HIF1A and HIF2A. Moreover, TCGA data revealed a correlation between CACNA1H methylation density and gene expression. Expression of rCacna1h in PC12 cells induced differential protein expression profiles, determined by mass spectrometry, as well as a shift in the membrane potential where maximum calcium currents were observed, as determined by electrophysiology. The findings suggest the involvement of CACNA1H/CaV3.2 in pheochromocytoma development and establish a potential link between the etiology of adrenomedullary and adrenocortical tumor development.

Atrophic changes in thyroid tumors are strong indicators of underlying DICER1 mutations: a bi-institutional genotype-phenotype correlation study.

Somatic and biallelic DICER1 mutations are reported in subsets of thyroid tumors, supporting the role of this gene in thyroid tumor development. As recent studies have brought attention to macrofollicular patterns, atrophic changes, and papillary structures as being associated with DICER1 mutations, we sought to explore these observations in a bi-institutional cohort. A total of 61 thyroid lesions (54 tumors and 7 cases of thyroid follicular nodular disease; TFND), including 26 DICER1 mutated and 35 DICER1 wildtype controls were subjected to histological re-investigation and clinical follow-up. DICER1-mutated lesions showed a statistically significant association with younger age at surgery (29.2 ± 12.5 versus 51.3 ± 18.8, p = 0.0001), a predominant macrofollicular growth pattern (20/26 mutated cases versus 18/35 wildtype; p = 0.01) and atrophic changes (20/26 mutated cases versus 2/35 wildtype; p = 0.0001). Similar results were obtained when excluding TFND cases. We also present clinical and histological triaging criteria for DICER1 sequencing of thyroid lesions, which led to the identification of DICER1 variants in 16 out of 26 cases (62%) when followed. Among these, 3 out of 12 cases with available data were found to carry a constitutional DICER1 mutation. This observation suggests that the majority of DICER1 mutations are somatic-however implies that sequencing of constitutional tissues could be clinically motivated. We conclude that DICER1 mutations are amassed in younger patients with macrofollicular-patterned tumors and, most strikingly, atrophic changes. Given the rate of constitutional involvement, our findings could be of clinical value, allowing the pathologist to triage cases for genetic testing based on histological findings.

Adrenal tumors in patients with neuroendocrine neoplasms.

PURPOSE: To study the prevalence of primary adrenal tumors and adrenal metastases in patients with neuroendocrine neoplasms (NENs) and describe these in detail. NENs can be further divided into neuroendocrine tumor (NET) and neuroendocrine carcinoma (NEC). METHODS: A review of medical files was conducted for all patients who underwent a 68Gallium-DOTATOC-PET/CT during 2010-2023 or adrenalectomy during 1999-2023 at the Karolinska University Hospital. RESULTS: In total, 68Gallium-DOTATOC-PET/CT was performed on 1750 individuals with NEN, among whom 12 (0.69%) had adrenal tumors. Of these, 9 (0.51%) were NEN metastases. Out of 1072 adrenalectomies, 4 (0.37%) showed evidence of NEN metastases. Thus, 16 patients with NEN exhibited adrenal tumors. The adrenal tumors were found on average 5 years after the NEN diagnosis and 19% of the adrenal tumors with simultaneous NEN were benign. Few had all adrenal hormones measured. None had an adrenal insufficiency nor an adrenal biopsy. Another synchronous metastasis was found in 69% at the time of the adrenal tumor discovery. During the median 2-year follow-up, 38% of the subjects had deceased (with the exclusion of individuals presenting supposedly benign adrenal tumors 31%) all due to tumor complications. A comparison between individuals identified through 68Gallium-DOTATOC-PET/CT and those who underwent adrenalectomy revealed a higher prevalence of NETs in the former group and NECs in the latter group. CONCLUSION: Adrenal primary tumors and adrenal metastases are infrequent occurrences in patients with NEN. Most cases involved the presence of NEN metastasis upon the initial discovery of adrenal tumors. The overall prognosis was found to be favorable.

Transplantation and Noninvasive Longitudinal In Vivo Imaging of Parathyroid Cells: A Proof-of-Concept Study.

The parathyroid cell is a vital regulator of extracellular calcium levels, operating through the secretion of parathyroid hormone (PTH). Despite its importance, the regulation of PTH secretion remains complex and not fully understood, representing a unique interplay between extracellular and intracellular calcium, and hormone secretion. One significant challenge in parathyroid research has been the difficulty in maintaining cells ex vivo for in-depth cellular investigations. To address this issue, we introduce a novel platform for parathyroid cell transplantation and noninvasive in vivo imaging using the anterior chamber of the eye as a transplantation site. We found that parathyroid adenoma tissue transplanted into the mouse eye engrafted onto the iris, became vascularized, and retained cellular composition. Transplanted animals exhibited elevated PTH levels, indicating a functional graft. With in vivo confocal microscopy, we were able to repetitively monitor parathyroid graft morphology and vascularization. In summary, there is a pressing need for new methods to study complex cellular processes in parathyroid cells. Our study provides a novel approach for noninvasive in vivo investigations that can be applied to understand parathyroid physiology and pathology under physiological and pathological conditions. This innovative strategy can deepen our knowledge on parathyroid function and disease.

The Evolutionary History of Metastatic Pancreatic Neuroendocrine Tumours Reveals a Therapy Driven Route to High-Grade Transformation.

Tumour evolution with acquisition of more aggressive disease characteristics is a hallmark of disseminated cancer. Metastatic pancreatic neuroendocrine tumours (PanNETs) in particular, show frequent progression from a low/intermediate to a high-grade disease. To understand the molecular mechanisms underlying this phenomenon, we performed multi-omics analysis of 32 longitudinal samples from six metastatic PanNET patients. Following MEN1 inactivation, PanNETs exhibit genetic heterogeneity on both spatial and temporal dimensions with parallel and convergent tumuor evolution involving the ATRX/DAXX and mTOR pathways. Following alkylating chemotherapy treatment, some PanNETs develop mismatch repair deficiency and acquire a hypermutator phenotype. This DNA hypermutation phenotype was only found in cases that also showed transformation into a high-grade PanNET. Overall, our findings contribute to broaden the understanding of metastatic PanNET, and suggests that therapy driven disease evolution is an important hallmark of this disease.

Spatial Transcriptomics in a Case of Follicular Thyroid Carcinoma Reveals Clone-Specific Dysregulation of Genes Regulating Extracellular Matrix in the Invading Front.

Follicular thyroid carcinoma (FTC) is recognized by its ability to invade the tumor capsule and blood vessels, although the exact molecular signals orchestrating this phenotype remain elusive. In this study, the spatial transcriptional landscape of an FTC is detailed with comparisons between the invasive front and histologically indolent central core tumor areas. The Visium spatial gene expression platform allowed us to interrogate and visualize the whole transcriptome in 2D across formalin-fixated paraffin-embedded (FFPE) tissue sections. Four different 6 × 6 mm areas of an FTC were scrutinized, including regions with capsular and vascular invasion, capsule-near area without invasion, and a central core area of the tumor. Following successful capturing and sequencing, several expressional clusters were identified with regional variation. Most notably, invasive tumor cell clusters were significantly over-expressing genes associated with pathways interacting with the extracellular matrix (ECM) remodeling and epithelial-to-mesenchymal transition (EMT). Subsets of these genes (POSTN and DPYSL3) were additionally validated using immunohistochemistry in an independent cohort of follicular thyroid tumors showing a clear gradient pattern from the core to the periphery of the tumor. Moreover, the reconstruction of the evolutionary tree identified the invasive clones as late events in follicular thyroid tumorigenesis. To our knowledge, this is one of the first 2D global transcriptional mappings of FTC using this platform to date. Invasive FTC clones develop in a stepwise fashion and display significant dysregulation of genes associated with the ECM and EMT - thus highlighting important molecular crosstalk for further investigations.

Prevalence, Molecular Landscape, and Clinical Impact of DICER1 and DGCR8 Mutated Follicular-Patterned Thyroid Nodules.

BACKGROUND: Mutations in micro-RNA (miRNA) regulators DICER1 and DGCR8 have recently been uncovered, revealing a potential novel mechanism driving thyroid tumor development. However, the true frequency of these hotspot mutations in follicular-patterned thyroid tumors (FTs) and their relation to established driver gene events remain elusive. METHODS: A total of 440 FTs from 2 institutions were interrogated for DICER1, DGCR8, and RAS family hotspot mutations using Sanger sequencing. Whole-exome sequencing was also performed to identify additional driver gene aberrations in DICER1/DGCR8-mutant cases. Subsets of cases were further analyzed using miRNA expression profiling, and key dysregulated miRNAs were validated as markers of DICER1 mutations using quantitative RT-PCR analysis. The Cancer Genome Atlas (TCGA) database was also probed for DICER1/DGCR8 mutations and miRNA dysregulation. RESULTS: Fourteen (3.2%) and 4 (1%) FTs harbored DICER1 and DGCR8 hotspot mutations, respectively, in the combined cohort, and no cases with normal tissue available were found to exhibit a constitutional variant. Two DGCR8-mutant cases also harbored oncogenic RAS mutations. Whole-exome sequencing analysis did not identify additional driver gene events in DICER1/DGCR8-positive cases. Comprehensive miRNA expression profiling revealed a unique pattern of dysregulated miRNAs in DICER1/DGCR8-mutant cases compared with wild-type lesions. Moreover, DICER1-mutant cases showed a remarkable reduction of 5' arm miRNAs, findings corroborated in the TCGA cohort. CONCLUSION: DICER1 and DGCR8 hotspot mutations are rare in unselected cohorts of FTs, and mutated cases exhibit a specific miRNA profile. Although DGCR8 mutations may coexist with established RAS gene alterations, FTs with DICER1 variants were devoid of other driver gene events.

A clinical perspective on ectopic Cushing's syndrome.

Cushing's syndrome (CS) refers to the clinical features of prolonged pathological glucocorticoid excess. About 10-20% of individuals with CS have ectopic CS (ECS), that is, an adrenocorticotropin (ACTH)-producing tumour outside the pituitary gland. ACTH-secreting neuroendocrine neoplasia (NENs) can arise from many organs, although bronchial NEN, small cell lung cancer (SCLC), pancreatic NEN, thymic NEN, medullary thyroid cancer (MTC), and pheochromocytoma are the most common. Patients with ECS frequently present with severe hypercortisolism. The risk of life-threatening complications is high in severe cases, unless the hypercortisolism is effectively treated. A good outcome in ECS requires a methodical approach, incorporating prompt diagnosis, tumour localization, control of cortisol excess, and resection of the primary tumour when possible.

Pitfalls in Thyroid Fine-Needle Aspiration Cytopathology: An Approach to Atypical Findings.

BACKGROUND: Thyroid nodules are prevalent among the general population, thus imposing substantial demands upon healthcare providers to establish effective management paradigms when investigating these lesions. A pivotal component in the diagnostic process involves the cytomorphological evaluation of fine-needle aspiration (FNA) specimens extracted from the nodule under scrutiny. This examination serves the critical purpose of enabling a comprehensive assessment for the risk of either a neoplasm or malignancy, thereby providing the clinical team with the requisite information to render decisions regarding potential surgical intervention and/or a structured clinical follow-up. A subset of FNA specimens obtained from the thyroid gland present a vexing challenge for interpretation and cannot be classified based on cytomorphology as either benign or malignant and are classified as "indeterminate" for neoplasm or malignancy. The indeterminate thyroid FNA diagnosis in the third iteration of the Bethesda classification is termed as "atypia of undetermined significance" (AUS). SUMMARY: The thyroid FNA specimens classified as "atypical" constitute a perplexing category, necessitating considerations such as repeated cytological evaluations, supplementary molecular analyses, diagnostic lobectomy, or vigilant surveillance. This review article draws upon the most recent Bethesda classification guidelines and delineates various potential pitfalls encountered during the interpretation of atypia observed in thyroid fine-needle aspiration and histopathologic counterparts. Additionally, it proffers strategic algorithms devised to effectively navigate these diagnostic challenges. KEY MESSAGES: It is important to recognize the value of an integrated approach when triaging AUS lesions, considering various clinical, morphological, and sometimes also immunocytochemical or molecular features.

Adrenal and periadrenal schwannoma: histological, molecular and clinical characterization of an institutional case series.

PURPOSE: Adrenal schwannoma (AS) and periadrenal schwannoma (PAS) are exceedingly rare Schwann cell tumors that develop from the adrenal medulla and periadrenal peripheral nerves respectively. The underlying genetic events are elusive. METHODS: We searched our institutional database for AS/PAS cases and reviewed the histology and clinical outcome. Comprehensive molecular work-up was performed. RESULTS: We found reports of 4 AS/PAS cases diagnosed between 1992 and 2022 among the 1248 adrenal lesions submitted for histopathology during the same time period (0.32%). Two patients were male, two were female, and the age span was 59-80 years. Median size was 70 mm (range 50-100 mm), and from a radiology perspective, the lesions were initially suspected of malignant lesions originating from either adrenals or kidneys. Hormonal analyses were normal in all cases. Histologically, three cases were annotated as cellular AS or PAS, and one case was annotated as microcystic AS. Molecular characterization using focused next-generation sequencing did not identify SMARCB1 or NF2 mutations, alterations previously associated to schwannoma at other anatomical sites. The postoperative period was without complications for all patients, and follow-up did not show any signs of relapse or metastatic disease. CONCLUSION: AS/PAS are rare neoplasms that are most often benign, and the molecular etiology is most likely not related to mutations in established schwannoma-related genes. Since these tumors may be misinterpreted as malignant, knowledge of this entity is essential for radiologists, endocrinologists, surgeons and pathologists.

5hmC Immunohistochemistry: A Predictor of TERT Promoter Mutational Status in Follicular Thyroid Carcinoma?

Telomerase reverse transcriptase (TERT) gene aberrancies correlate to adverse prognosis in follicular thyroid carcinoma (FTC). As loss of 5-hydroxymethylcytosine (5hmC) has been associated with TERT promoter mutations in papillary thyroid carcinoma, this study sought to analyze the levels of 5hmC in a cohort of follicular thyroid tumors with available TERT data. A total of 29 tumors (26 FTCs, 2 follicular thyroid tumors of uncertain malignant potential, and 1 oncocytic thyroid carcinoma) with known TERT promoter mutational status and TERT gene expression were assessed for 5hmC immunoreactivity using two antibodies (clones RM236 and 4D9.) Slides were analyzed using a semiquantitative scoring system. Of the 10 tumor cases with aberrant TERT, only 1 scored negative with both antibodies (1/10; 10%), whereas the remaining 9 cases (9/10; 90%) exhibited some positivity for at least one antibody. Of the 19 TERT wild-type tumors, no case was scored negative using RM236, and 2 cases (2/19; 11%) using 4D9. The differences between TERT promoter mutated and wild-type groups were non-significant. The sensitivity and specificity for 5hmC immunohistochemistry (IHC) to detect mutated cases were 10% and 100% (RM236) and 20% and 89% (4D9). Therefore, 5hmC IHC is not a sensitive marker for detecting TERT promoter mutations in follicular thyroid tumors.

Primary tumour iodine avidity in relation to uptake in persistent metastatic disease in papillary and poorly differentiated thyroid cancer.

PURPOSE: Patients with persistent or recurrent papillary and poorly differentiated thyroid cancer can be effectively treated with radioiodine, if the tumour tissue is iodine-avid. However, iodine-avidity status is often unknown at the time of initial radioiodine treatment, limiting any adaptive approach. This study aimed to clarify the relationship between pre-therapeutic iodine avidity in primary tumour tissue, initial lymph node metastases and iodine uptake in subsequent metastases. METHODS: Iodine avidity was prospectively assessed pre-therapeutically in 35 patients by injection of tracer amounts of iodine-131 two days prior to surgery. Iodine concentrations in resected tissue samples were measured, enabling accurate and histologically verifiable iodine avidity data for both primary tumour and initial lymph node metastases. Iodine uptake in persistent metastatic disease was assessed by review of radiology, and treatment response was examined through journal studies. RESULTS: Out of data from 35 patients, 10 had persistent disease at presentation or during follow-up (range 19-46 months). Four patients had non-avid persistent metastatic disease, all with low iodine avidity in their primary tumours and initial lymph node metastases. Patients with low pre-therapeutic iodine avidity did not appear to have greater risk of persistent disease. CONCLUSION: The results indicate a close link between pre-therapeutically measured iodine concentrations in primary tumours with iodine avidity of any subsequent metastases.

Iodine avidity in papillary and poorly differentiated thyroid cancer is predicted by immunohistochemical and molecular work-up.

Background: Successful radioiodine treatment of differentiated thyroid cancer requires iodine avidity: that is, the concentration and retention of iodine in cancer tissue. Several parameters have previously been linked with lower iodine avidity. However, a comprehensive analysis of which factors best predict iodine avidity status, and the magnitude of their impact, is lacking. Methods: Quantitative measurements of iodine avidity in surgical specimens (primary tumour and lymph node metastases) of 28 patients were compared to immunohistochemical expression of the thyroid-stimulating hormone receptor, thyroid peroxidase (TPO), pendrin, sodium-iodide symporter (NIS) and mutational status of BRAF and the TERT promoter. Regression analysis was used to identify independent predictors of poor iodine avidity. Results: Mutations in BRAF and the TERT promoter were significantly associated with lower iodine avidity for lymph node metastases (18-fold and 10-fold, respectively). Membranous NIS localisation was found only in two cases but was significantly associated with high iodine avidity. TPO expression was significantly correlated with iodine avidity (r = 0.44). The multivariable modelling showed that tumour tissue localisation (primary tumour or lymph node metastasis), histological subtype, TPO and NIS expression and TERT promoter mutation were each independent predictors of iodine avidity that could explain 68% of the observed variation of iodine avidity. Conclusions: A model based on histological subtype, TPO and NIS expression and TERT promoter mutation, all evaluated on initial surgical material, can predict iodine avidity in thyroid cancer tissue ahead of treatment. This could inform early adaptation with respect to expected treatment effect.

Adrenal cysts: an emerging condition.

Adrenal cysts are rare lesions representing approximately 1-2% of adrenal incidentalomas. The majority of these rare lesions are benign. Rarely, phaeochromocytomas and adrenal malignant masses can present as cystic lesions and can occasionally be difficult to distinguish from benign cysts. Histologically, adrenal cysts are subdivided into pseudocysts, endothelial cysts, epithelial cysts and parasitic cysts. The radiological appearance of an adrenal cyst is generally similar to that of cysts in the kidney. They are thus well demarcated, usually rounded, with a thin wall and homogenous internal structure, low attenuating (<20 Hounsfield Units) on CT, low signalling on T1-weighted MRI sequences and high signalling on T2-weighted MRI sequences, and anechoic or hypoechoic on ultrasonography. Benign adrenal cysts have a slight female predominance and are usually diagnosed between the ages of 40 and 60. Most adrenal cysts are asymptomatic and are detected incidentally, although very large adrenal cysts can lead to mass effect symptoms, with surgery required to alleviate the symptoms. Thus, conservative management is usually recommended for asymptomatic cysts. However, when uncertainty exists regarding the benign nature of the cyst, additional work-up or follow-up is needed. The management of an adrenal cyst should preferably be discussed at an adrenal multidisciplinary team meeting.

Top 10 Histological Mimics of Neuroendocrine Carcinoma You Should Not Miss in the Head and Neck.

BACKGROUND: The spectrum of neuroendocrine neoplasia (NEN) of the head and neck region is wide-ranging and diverse, including a variety of diagnoses stretching from benign and low-malignant tumor forms to highly proliferative, poor prognosis neuroendocrine carcinoma (NEC). Moreover, there are several non-neuroendocrine differential diagnoses to keep in mind as well, displaying various degree of morphological and/or immunohistochemical overlap with bona fide neuroendocrine lesions. METHODS: Review. RESULTS: While the growth patterns may vary, well-differentiated NEN usually display a stippled "salt and pepper" chromatin, a granular cytoplasm, and unequivocal expression of neuroendocrine markers such as chromogranin A and synaptophysin. However, these features are often less pronounced in NEC, which may cause diagnostic confusion-not the least since several non-NEC head and neck tumors may exhibit morphological similarities and focal neuroendocrine differentiation. CONCLUSION: As patients with NEC may require specific adjuvant treatment and follow-up, knowledge regarding differential diagnoses and potential pitfalls is therefore clinically relevant. In this review, the top ten morphological and/or immunohistochemical mimics of NEC are detailed in terms of histology, immunohistochemistry, and molecular genetics.