Clinical and Pathological Features and Gene Expression Profiles of Clinically Aggressive Papillary Thyroid Carcinomas.

Papillary thyroid carcinoma (PTC) is considered an indolent neoplasm but it may demonstrate aggressive behavior. We aimed to identify clinical and pathological characteristics and molecular signatures associated with aggressive forms of PTCs. We selected 43 aggressive PTC cases based on the presence of metastases at the time of diagnosis, the development of distant metastasis during follow-up, and/or biochemical recurrence, and 43 PTC patients that were disease-free upon follow-up, matching them according to age, sex, pT, and pN parameters. Twenty-four pairs (a total of 48 cases) and 6 normal thyroid tissues were studied using targeted mRNA screening of cancer-associated genes employing NanoString nCounter® technology. In general, aggressive PTCs showed distinctive clinical and morphological features. Among adverse prognostic parameters, the presence of necrosis and an increased mitotic index were associated with shorter disease-free and overall survivals. Other parameters associated with shorter disease-free or overall survivals include a lack of tumor capsule, the presence of vascular invasion, tumor-infiltrating lymphocytes, fibrosclerotic changes, age > 55 years, and a high pTN stage. Various pathways were differentially regulated in non-aggressive as compared to aggressive PTC, including the DNA damage repair, the MAPK, and the RAS pathways. In particular, the hedgehog pathway was differentially de-regulated in aggressive PTC as compared to non-aggressive PTC cases, being WNT10A and GLI3 genes significantly up- and down-regulated in aggressive PTC and GSK3B up-regulated in non-aggressive PTC cases. In conclusion, our study revealed specific molecular signatures and morphological features in aggressive PTC that may be useful to predict more aggressive behavior in a subset of PTC patients. These findings may be useful when developing novel, tailored treatment options for these patients.

Solitary fibrous tumor of the thyroid: report of three cases with a focus on cytological features and histological clues for malignancy.

Solitary fibrous tumor is a mesenchymal tumor of intermediate malignant potential characterized by a recurrent NAB2::STAT6 fusion and STAT6 nuclear expression. Primary thyroid solitary fibrous tumor is relatively uncommon, with 45 cases described in the English literature to date. Although its histologic features are characteristic, its diagnosis in the thyroid can be problematic, especially in small biopsies or cytology specimens. We herein present three new cases of thyroid solitary fibrous tumor, one of which is malignant, with new insights on the morphological spectrum and malignant potential of this tumor. We additionally provide a review of the literature with a focus on the clues and challenges of a preoperative cytological diagnosis of this tumor, which can nowadays be supported by STAT6 nuclear expression, when appropriately suspected.

Endobronchial Inflammatory Myofibroblastic Tumor in a 3-Year-Old Child.

Inflammatory myofibroblastic tumor (IMT) is a mesenchymal tumor that can occur at any age. However, it is primarily seen in children, with the most common site being in the lung parenchyma, usually present with rare endobronchial lesions. This case reports the incidence in a 3-year-old girl diagnosed with pericardiac pneumonia treated with antibiotics with no clinical improvement. A chest computed tomography (CT) scan identified a 1.5-cm lesion in the left main bronchus. Bronchoscopy revealed complete obstruction of the left main stem bronchus. A left posterolateral thoracotomy was performed. Additionally, a left sleeve upper bronchial resection was conducted under fibroendoscopic control. Definitive histology confirmed IMT. After 2 years of endoscopic follow-up, there is no evidence of recurrence.

New Onset of Giant Cell Arteritis following ChAdOx1-S (Vaxevria®) Vaccine Administration.

We report a 78-year-old man presenting with persistent headaches in vertex and temporo-parietal area; fatigue, worsening after walking; jaw claudication; scotomas; pharyngodynia; and dry cough after the second dose of the SARS-CoV-2 vaccine (ChAdOx1-S) administration. Laboratory findings showed an elevated C-reactive protein level and FDG-CT PET showed evidence of active large vessel vasculitis with diffuse abnormal artery uptake. Under suspicion of vasculitis, a temporal arteries biopsy was performed; the histopathologic findings demonstrated the transmural inflammatory infiltrate with giant cells, compatible with giant cell arteritis. Although the overall incidence of vaccine-triggered autoimmunity is low, rheumatologists worldwide should be aware of autoimmune diseases as a new potential adverse event of vaccines.

Early post-liver transplant use of direct-acting antivirals in naive and NS5A inhibitor-experienced HCV patients.

Direct-acting antiviral drugs (DAA) are safe and effective in the HCV population. However, in patients with decompensated cirrhosis and/or active hepatocellular carcinoma or relapse to NS5A inhibitors, response rates are lower and DAA therapy must be postponed until after liver transplant in an era of organ shortage and suboptimal donors. We aimed to assess the prevalence of patients still HCV infected at time of transplantation over the last 3 years in our Center and describe the safety and efficacy of DAA therapy started as soon as possible after surgery. We enrolled all HCV viraemic patients transplanted in our Centre from January 2019 to March 2022. The follow-up was closed in July 2022. Among 490 liver transplants, 49 (10%) patients were still HCV viraemic at operation, 43 naive to DAA and 6 were NS5A-experienced. Median donor age was 64 years; donor risk index was 1.8. In naive patients, sofosbuvir/velpatasvir was started after a median time of 1 day from surgery, while in NS5A-experienced sofosbuvir/velpatasvir/voxilaprevir after 14.5 days (p = .001). Response rate was 98%. 1 NS5A-experienced patient experienced acute cholestatic hepatitis which promptly reverted after permanent DAA discontinuation. Hence, very early post-liver transplant HCV eradication was safe and effective thanks to a close teamwork which involved anaesthesiologists, transplant surgeons and hepatologists.

From SGAP-Model to SGAP-Score: A Simplified Predictive Tool for Post-Surgical Recurrence of Pheochromocytoma.

A reliable prediction of the recurrence risk of pheochromocytoma after radical surgery would be a key element for the tailoring/personalization of post-surgical follow-up. Recently, our group developed a multivariable continuous model that quantifies this risk based on genetic, histopathological, and clinical data. The aim of the present study was to simplify this tool to a discrete score for easier clinical use. Data from our previous study were retrieved, which encompassed 177 radically operated pheochromocytoma patients; supervised regression and machine-learning techniques were used for score development. After Cox regression, the variables independently associated with recurrence were tumor size, positive genetic testing, age, and PASS. In order to derive a simpler scoring system, continuous variables were dichotomized, using > 50 mm for tumor size, ≤ 35 years for age, and ≥ 3 for PASS as cut-points. A novel prognostic score was created on an 8-point scale by assigning 1 point for tumor size > 50 mm, 3 points for positive genetic testing, 1 point for age ≤ 35 years, and 3 points for PASS ≥ 3; its predictive performance, as assessed using Somers' D, was equal to 0.577 and was significantly higher than the performance of any of the four dichotomized predictors alone. In conclusion, this simple scoring system may be of value as an easy-to-use tool to stratify recurrence risk and tailor post-surgical follow-up in radically operated pheochromocytoma patients.

Clinical-Pathological Evaluation and Prognostic Analysis of 228 Merkel Cell Carcinomas Focusing on Tumor-Infiltrating Lymphocytes, MCPYV Infection and ALK Expression.

Merkel cell carcinoma is a rare and aggressive primary neuroendocrine carcinoma of the skin, whose pathogenesis can be traced back to UV radiation damage or Merkel cell polyomavirus (MCPyV) infection. Despite some improvements on the characterization of the disease partly due to its increased incidence, crucial pathogenetic and prognostic factors still need to be refined. A consecutive series of 228 MCC from three hospitals in Turin was collected with the aim of both analyzing the apparent increase in MCC incidence in our area and investigating the distribution and prognostic role of clinical-pathological parameters, with a focus on MCPyV status, ALK tumor expression and tumor infiltrating lymphocytes (TILs). Review of morphology and conventional immunohistochemical staining was possible in 191 cases. In 50 cases, the expression of the novel neuroendocrine marker INSM1 was additionally assessed. Fourteen cases of MCC of unknown primary skin lesion were identified and separately analyzed. While confirming an exponential trend in MCC incidence in the last decades and providing a description of histological and cytological features of a large series of MCC, the present study concludes that 1) INSM1 is a highly sensitive marker in both skin and lymph node primary MCC; 2) positive MCPyV status, brisk TILs and lower tumor size and thickness are independent positive prognostic parameters, and the combination of the former two may provide a novel tool for prognostic stratification; 3) ALK is expressed 87% of MCC and associated with positive viral status, and could represent a prognostic biomarker, if validated in larger series.

External Validation of Three Available Grading Systems for Medullary Thyroid Carcinoma in a Single Institution Cohort.

Medullary thyroid carcinoma (MTC) is a rare thyroid carcinoma with a variable clinical behavior. Potential clinical and pathological prognostic markers have been investigated, but studies are limited and controversial. In neuroendocrine neoplasms of various other sites, necrosis and proliferation (mitotic activity and/or Ki67 index) are integrated to provide a histological grade. Recently, an International Medullary Thyroid Carcinoma Grading System (IMTCGS) has been designed to define high- or low-grade MTC by combining proliferative activity and necrosis. This proposal integrates two previously published grading schemes by American (2-tiered grading, low- and high-grade MTC) and Australian authors (3-tiered grading, low-, intermediate-, and high-grade MTC). To validate the clinical role of these systems, their prognostic impact was evaluated in an independent cohort of 111 MTCs. Necrosis, which was the only parameter integrated into the 3 grading systems, proved to be individually correlate with tumor relapse, while no association was found with the proliferation (mitotic count and Ki67 index); however, by combining the different parameters according to all three grading systems, "high-grade" MTCs turned out to be significantly associated with the disease recurrence (p < 0.005) in all systems. In disease-free survival analysis, the IMTCGS stratification was the only one that demonstrated a significant impact at Cox regression analysis (p = 0.004), further confirmed by the Kaplan-Meier curves (p = 0.002). Similar findings were also reproduced when analysis was restricted to sporadic MTCs (68 cases). In conclusion, our results confirm the prognostic role of IMTCGS, supporting the importance of incorporating this information into the pathology report. However, none of the systems proved to predict the overall survival in this validation cohort.

Development and internal validation of a predictive model for the estimation of pheochromocytoma recurrence risk after radical surgery.

Objective: Various features have been identified as predictors of relapse after complete resection of pheochromocytoma, but a comprehensive multivariable model for recurrence risk prediction is lacking. The aim of this study was to develop and internally validate an integrated predictive model for post-surgical recurrence of pheochromocytoma. Methods: The present research retrospectively enrolled 177 patients affected by pheochromocytoma and submitted to radical surgery from 1990 to 2016, in nine referral centers for adrenal diseases. Cox regression analysis was adopted for model development, and a bootstrapping procedure was used for internal validation. Results: Variables independently associated with recurrence were tumor size (hazard ratio (HR): 1.01, 95% CI: 1.00-1.02), positive genetic testing (HR: 5.14, 95% CI: 2.10-12.55), age (HR: 0.97, 95% CI: 0.94-0.99), and Pheochromocytoma of the Adrenal Gland Scaled Score (PASS) (HR: 1.16, 95% CI: 1.04-1.29). The predictive performance of the overall model, evaluated by Somers' D, was equal to 0.594, and was significantly higher than the ones of any single predictor alone (P = 0.002 compared to tumor size; P = 0.004 compared to genetic testing; P = 0.048 compared to age; P = 0.006 compared to PASS). Internal validation by bootstrapping techniques estimated an optimistic bias of 6.3%, which reassured about a small tendency towards overfit. Conclusions: We proposed a multivariable model for the prediction of post-surgical recurrence of pheochromocytoma, derived by the integration of genetic, histopathological, and clinical data. This predictive tool may be of value for a comprehensive tailoring of post-surgical follow-up in radically operated pheochromocytoma patients.

Impact of Macroscopic On-Site Evaluation (MOSE) on Accuracy of Endoscopic Ultrasound-Guided Fine-Needle Biopsy (EUS-FNB) of Pancreatic and Extrapancreatic Solid Lesions: A Prospective Study.

This is a prospective and comparative study including 76 consecutive patients performing EUS-FNB for pancreatic and extrapancreatic solid lesions, randomized by alternate allocation to macroscopic on-site evaluation (MOSE) (40 patients) or to a conventional technique (40 patients), with three passes each. MOSE samples were differentiated into score 0: no visible material, score 1: only necrotic or haematic material, score 2: white core tissue ≤ 2 mm, or score 3: white core tissue > 2 mm. The conventional technique consisted in pushing all the needle content into a test tube for evaluation by the pathologist. In both groups, a 22-25 Gauge Franseen-tip needle (Acquire, Boston Scientific Co., Natick, MA, USA) was used. The study evaluated the diagnostic accuracy and adequacy of MOSE compared to the conventional technique and whether MOSE could optimize the number of passes during EUS-FNB. Results: The analysis was performed on 76 patients (38 MOSE, 38 conventional). The overall diagnostic adequacy was 94.7% (72/76) and accuracy was 84.2% (64/76). The diagnostic accuracy was similar in the two groups: MOSE 86.8% (33/38 lesions), vs. conventional 81.6%, 31/38 lesions, p = 0.76). Regarding diagnostic adequacy, the MOSE technique was 97.4% (111/114 passes) compared to 92.1% (105/114 passes) with the conventional technique, p = 0.06. The accuracy increased according to the MOSE score evaluation: it was 43.5%, 65.5% and 78.3% in patients with score 1, score 2, and score 3, respectively. Moreover, if in the first two passes the MOSE score was 2 or 3, the accuracy was 82.6% (20/23), and upon adding a third pass, the accuracy increased to 87% (20/23), which was not significantly different from the general accuracy of the MOSE samples (86.8%) (p = 0.86). Conclusions: The MOSE score showed a comparable diagnostic accuracy to the conventional technique. However, MOSE allows endoscopists to perform an inspective evaluation of the material, tends to perform better than the conventional technique in terms of diagnostic adequacy, and may potentially reduce the number of passes.

Co-occurrence of mutations in NF1 and other susceptibility genes in pheochromocytoma and paraganglioma.

Introduction: The percentage of patients diagnosed with pheochromocytoma and paraganglioma (altogether PPGL) carrying known germline mutations in one of the over fifteen susceptibility genes identified to date has dramatically increased during the last two decades, accounting for up to 35-40% of PPGL patients. Moreover, the application of NGS to the diagnosis of PPGL detects unexpected co-occurrences of pathogenic allelic variants in different susceptibility genes. Methods: Herein we uncover several cases with dual mutations in NF1 and other PPGL genes by targeted sequencing. We studied the molecular characteristics of the tumours with co-occurrent mutations, using omic tools to gain insight into the role of these events in tumour development. Results: Amongst 23 patients carrying germline NF1 mutations, targeted sequencing revealed additional pathogenic germline variants in DLST (n=1) and MDH2 (n=2), and two somatic mutations in H3-3A and PRKAR1A. Three additional patients, with somatic mutations in NF1 were found carrying germline pathogenic mutations in SDHB or DLST, and a somatic truncating mutation in ATRX. Two of the cases with dual germline mutations showed multiple pheochromocytomas or extra-adrenal paragangliomas - an extremely rare clinical finding in NF1 patients. Transcriptional and methylation profiling and metabolite assessment showed an "intermediate signature" to suggest that both variants had a pathological role in tumour development. Discussion: In conclusion, mutations affecting genes involved in different pathways (pseudohypoxic and receptor tyrosine kinase signalling) co-occurring in the same patient could provide a selective advantage for the development of PPGL, and explain the variable expressivity and incomplete penetrance observed in some patients.

"Never Trust to General Impressions, My Boy, but Concentrate Yourself upon Details": An Unusual and Challenging Presentation of Pheochromocytoma.

We present the case of a 45-year-old woman admitted to our unit with acute heart failure and cardiogenic shock, requiring an intra-aortic balloon pump insertion and inotropes and vasopressors infusion. Despite such treatment, the patient developed multi organ failure and intravascular disseminated coagulation with haemolysis. The initial diagnosis of acute myocarditis was subsequently denied by the finding of bilateral adrenal masses by MRI scan, and urine and plasma metanephrines measurements confirmed a pheochromocytoma (PCC). Genetic analysis revealed a mutation in the neurofibromatosis type 1 (NF1) gene, and an accurate physical examination drew attention to small cafè-au-lait spots, usually associated with this syndrome. PCC diagnosis should be promptly considered in patients presenting with unexplained acute heart failure and cardiogenic shock of unknown origin, considering its life-threatening complications and the good prognosis after radical surgery.

Predictor Analysis in Radiofrequency Ablation of Benign Thyroid Nodules: A Single Center Experience.

Purpose: To confirm the efficacy of ultrasound (US) guided radiofrequency ablation (RFA) in the treatment of benign thyroid nodules, we evaluated as primary outcome the technical efficacy and clinical success in a single center dataset. The secondary outcome was to find a correlation between nodules' pre-treatment features and volume reduction rate (VRR) ≥75% at 12 months after RFA and during follow-up period. Methods: This retrospective study included 119 consecutive patients (99 females, 20 males, 51.5 ± 14.4 years) with benign thyroid nodules treated in our hospital between October 2014 and December 2018 with a mean follow-up of 26.8 months (range 3-48). Clinical and US features before and after RFA were evaluated by a US examination at 1, 3, 6, 12 months and annually thereafter up to 48 months. Results: The median pre-treatment volume was 22.4 ml; after RFA we observed a statistically significant volume reduction from the first month (11.7 ml) to the last follow-up (p < 0.001 for all follow-up times). The median VRR was 47.1, 55.3, 61.2, 67.6, 72.8, 71.3, and 62.9% at 1, 3, 6, 12, 24, 36, and 48 months of follow-up respectively, showing a progressive significant improvement up to 24 months (VRRs 1 vs 3 months, 3 vs 6 months and 6 vs 12 months p < 0.001, 12 vs 24 months p = 0.05) while no differences at 24 vs 36 and 36 vs 48 months were observed. Symptoms improved significantly (complete resolution 64.35%, partial resolution 35.65%), and neck circumference was reduced as compared to pre-treatment (p < 0.001). Lower pre-treatment neck circumference (37.5 vs 36.0 cm, p = 0.01) was a positive predictor of VRR ≥75% at 12 months. Macrocystic echostructure (HR 2.48, p 0.046) and pre-treatment volume >22.4 ml (HR 0.54, p 0.036) were found to be independent positive and negative predictors of VRR ≥75% respectively. One-month post RFA VRR ≥50% represented the best positive predictor of technical success. Conclusions: This study confirmed the efficacy of RFA in the treatment of benign thyroid nodules. In particular we show that by selecting macrocystic nodules smaller than 22.4 ml better long-term response can be achieved, which is predicted by an early shrinkage of the nodule.

Intron 4-5 hTERT DNA Hypermethylation in Merkel Cell Carcinoma: Frequency, Association with Other Clinico-pathological Features and Prognostic Relevance.

Merkel cell carcinoma (MCC) is an aggressive skin tumor with neuroendocrine differentiation, mainly affecting elderly population or immunocompromised individuals. As methylation of the human telomerase reverse transcriptase (mhTERT) has been shown to be a prognostic factor in different tumors, we investigated its role in MCC, in particular in intron 4-5 where rs10069690 has been mapped and recognized as a cancer susceptibility locus. DNA methylation analysis of hTERT gene was assessed retrospectively in a cohort of 69 MCC patients from the University of Bologna, University of Turin and University of Insubria. Overall mortality was evaluated with Kaplan-Meier curves and multivariable Royston-Parmar models. High levels of mhTERT (mhTERThigh) (HR = 2.500, p = 0.015) and p63 (HR = 2.659, p = 0.016) were the only two clinico-pathological features significantly associated with a higher overall mortality at the multivariate analysis. We did not find different levels of mhTERT between MCPyV (+) and (-) cases (21 vs 14, p = 0.554); furthermore, mhTERThigh was strongly associated with older age (80.5 vs 72 years, p = 0.026), no angioinvasion (40.7% vs 71.0%, p = 0.015), lower Ki67 (50 vs 70%, p = 0.005), and PD-L1 expressions in both tumor (0 vs 3%, p = 0.021) and immune cells (0 vs 10%, p = 0.002). mhTERT is a frequently involved epigenetic mechanism and a relevant prognostic factor in MCC. In addition, it belongs to the shared oncogenic pathways of MCC (MCPyV and UV-radiations) and it could be crucial, together with other epigenetic and genetic mechanisms as gene amplification, in determining the final levels of hTERT mRNA and telomerase activity in these patients.

Radiofrequency Thermal Ablation for a Small Papillary Thyroid Carcinoma in a Patient Unfit for Surgery: A Case Report.

Ultrasound-guided radiofrequency thermal ablation has been proposed as an effective and safe procedure for treating patients who have low-risk papillary thyroid microcarcinomas and/or are unfit for surgery. We present the case of a 72-year old male patient with a small thyroid nodule diagnosed as papillary carcinoma after fine needle aspiration. Since the patient had other serious comorbidities, priority was given to other therapies and the malignant thyroid nodule was submitted to active surveillance. After detecting at a follow-up examination a slight dimensional increase of the nodule, the possibility of a radiofrequency thermal ablation was proposed to our patient, who accepted. The procedure was safely and effectively carried out. Follow-up examinations with ultrasonography (or contrast enhanced ultrasound), conducted after 1, 3, 6, and 12 months, demonstrated a progressive reduction of size and loss of vascularization in the treated area. The fine needle aspiration was repeated after 6 months: the sample revealed a very poor cellularity composed of inflammatory cells and thick colloid; no residual neoplastic cells were observed. Our experience confirmed what already demonstrated by previous reports: radiofrequency ablation can effectively eliminate small papillary carcinomas, with a very low complication rate. It may be an alternative strategy for the treatment of low-risk, indolent papillary thyroid microcarcinomas, thus avoiding the potential side-effects of surgery in patients at risk for relevant comorbidities.

Neuroendocrine neoplasms of the appendix, colon and rectum.

Neuroendocrine neoplasms of the appendix, colon and rectum are classified according to the most recent WHO classification as neuroendocrine tumors (NET), neuroendocrine carcinomas (NEC) and mixed neuroendocrine-non neuroendocrine neoplasms (MiNENs). NECs and MiNENs are aggressive neoplasms requiring multimodal treatment strategies. By contrast, NETs are, in most cases, indolent lesions occurring as incidental findings in the appendix or as polyps in the rectum. While most appendiceal and rectal NETs are considered relatively non-aggressive neoplasms, a few cases, may show a more aggressive clinical course. Unfortunately, clinical/pathological characteristics to select patients at high risk of recurrence/metastases are poorly consolidated. Diagnosis is generally easy and supported by the combination of morphology and immunohistochemistry. Differential diagnostic problems are for NECs/MiNENs with poorly differentiated adenocarcinomas, when immunohistochemical neuroendocrine markers are not obviously positive, whereas for NETs they are represented by the rare appendiceal tubular and clear cell variants (which may be confused with non-neuroendocrine cancers) and rectal L-cell tumors which may be chromogranin negative and prostatic marker positive.

Malignant struma ovarii: next-generation sequencing of six cases revealed Nras, Braf, and Jak3 mutations.

PURPOSE: Struma ovarii (SO) is a highly specialized ovarian teratoma, consisting of thyroid tissue. Rarely, carcinomas histologically identical to their thyroid counterparts may occur, and are comprehensively defined as malignant struma ovarii (MSO). Their optimal management is controversial, and the molecular profile of the malignant counterpart in the ovary is incompletely known. In this study, the clinicopathological and molecular features of six MSO from different Italian Institutions were analysed, to explore genetic profiles of potential therapeutic interest. METHODS: The histopathological features and immunoprofile (according to the known markers Galectin-3, HBME1, cytokeratin 19 and CD56) were reviewed. In addition, all cases underwent genetic analysis with a next-generation sequencing (NGS) hot spot cancer panel detecting mutations in 50 genes involved in cancerogenesis. RET/PTC rearrangements and TERT promoter alterations were also evaluated. RESULTS: Papillary carcinoma in all similar to its thyroid counterpart was found in five of six cases, including classical (two tumors) and follicular variant (three tumors) types. The last case was a poorly differentiated carcinoma. An activating gene mutation, was detected in five of six cases, including two NRAS, two BRAF, and one JAK3 oncogene mutations. No alterations were found in the other panel genes, nor in TERT promoter, or in RET chromosomal regions. CONCLUSIONS: MSO is a rare condition. Papillary carcinoma is the predominant malignant type, sharing both histomorphological and molecular features of its thyroid counterpart. Interestingly, the single case of poorly differentiated carcinoma displayed a JAK3 mutation. The presence of such driving mutation could be of potential interest in guiding postoperative treatment.

Amyloid-Rich Pancreatic Neuroendocrine Tumors: a Potential Diagnostic Pitfall in Endoscopic Ultrasound-Guided Fine Needle Aspiration Cytology (EUS-FNAC).

Pancreatic neuroendocrine tumors (PanNETs) are rare neoplasms that include even rarer variants that may pose different diagnostic problems, especially in fine needle aspiration cytology (FNAC). We describe the diagnostic clues of the amyloid-rich variant of PanNETs in endoscopic ultrasound (EUS)-guided fine needle aspiration cytology (EUS-FNAC). Three cases of PanNETs with an amyloid-rich stromal component were retrieved and retrospectively reviewed. For every case, the pancreatic lesion was investigated by a EUS-FNAC procedure. The final diagnosis was supported by immunocytochemistry and Congo red staining. All cases had similar EUS-FNAC features: neoplastic cells were entrapped in an eosinophilic, homogeneous dense and amorphous matrix. The neuroendocrine nature was confirmed by immunoexpression of synaptophysin and chromogranin A, while the amorphous stroma was characterized as amyloid based on positive Congo red staining. Regarding the hormonal profile, no insulin or proinsulin reactivity was observed, but all cases were diffusely positive for amylin. The diagnosis of uncommon variants of PanNETs, such as the amyloid-rich, is challenging especially in EUS-FNAC procedures because of a unique and misleading morphology, potentially mimicking fibrotic conditions and amyloid deposition within systemic amyloidosis. In cytology specimens, the presence of amorphous material requires amyloid deposition to be considered in the differential diagnosis of pancreatic neoplasms with neuroendocrine phenotype.