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Some hepatocellular adenoma (HCA) subtypes are characterized by different CTNNB1 mutations, leading to different beta-catenin activation levels, hence variable immunostaining patterns of glutamine synthetase (GS) expression, and different risks of malignant transformation. In a retrospective multicentric study of 63 resected inflammatory (n=33) and noninflammatory (n=30) molecularly confirmed CTNNB1-mutated b-(I)HCA, we investigated the predictive potential of 3 known GS patterns as markers for CTNNB1 exon 3, 7/8 mutations. Pattern 1 (diffuse homogenous) allowed recognition of 17/21 exon 3 non-S45 mutated b-(I)HCA. Pattern 2 (diffuse heterogenous) identified all b-(I)HCA harboring exon 3 S45 mutation (20/20). Pattern 3 (focal patchy) distinguished 12/22 b-(I)HCA with exon 7/8 mutations. In exon 3 S45 and 7/8 mutations, both b-HCA and b-IHCA showed a GS+/CD34- rim with diffuse CD34 positivity in the center of the lesion. Interobserver reproducibility was excellent for exon 3 mutations. Comparative analysis of GS patterns with molecular data showed 83% and 80% sensitivity (b-HCA/b-IHCA) and 100% specificity for exon 3 non-S45. For exon 3 S45, sensitivity was 100% for b-(I)HCA, and specificity 93% and 92% (b-HCA/b-IHCA). For exon 7/8, sensitivity was 55% for both subtypes and specificity 100% and 96% (b-HCA/b-IHCA). Preliminary data from 16 preoperative needle biopsies from the same patients suggest that this panel may also be applicable to small samples. In surgically resected HCA, 2 distinct GS patterns can reliably predict CTNNB1 exon 3 mutations, which are relevant because of the higher risk for malignant transformation. The third pattern, although specific, was less sensitive for the identification of exon 7/8 mutation, but the GS+/CD34- rim is a valuable aid to indicate either an exon 3 S45 or exon 7/8 mutation., Competing Interests: Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Characteristic but rare vascular neoplasms in the adult liver composed of small vessels with an infiltrative border were collected from an international group of collaborators over a 5-year period (N=17). These tumors were termed hepatic small vessel neoplasm (HSVN), and the histologic differential diagnosis was angiosarcoma (AS). The average age of patients was 54years (range, 24-83years). HSVN was more common in men. The average size was 2.1cm (range, 0.2-5.5cm). Diagnosis was aided by immunohistochemical stains for vascular lineage (CD31, CD34, FLI-1), which were uniformly positive in HSVN. Immunohistochemical stains (p53, c-Myc, GLUT-1, and Ki-67) for possible malignant potential are suggestive of a benign/low-grade tumor. Capture-based next-generation sequencing (using an assay that targets the coding regions of more than 500 cancer genes) identified an activating hotspot GNAQ mutation in 2 of 3 (67%) tested samples, and one of these cases also had a hotspot mutation in PIK3CA. When compared with hepatic AS (n=10) and cavernous hemangioma (n=6), the Ki-67 proliferative index is the most helpful tool in excluding AS, which demonstrated a tumor cell proliferative index greater than 10% in all cases. Strong p53 and diffuse c-Myc staining was also significantly associated with AS but not with HSVN or cavernous hemangioma. There have been no cases with rupture/hemorrhage, disseminated intravascular coagulation, or Kasabach-Merritt syndrome. Thus far, there has been no metastasis or recurrence of HSVN, but complete resection and close clinical follow-up are recommended because the outcome remains unknown.

Simple Summary: In recent years, significant progress has been made in elucidating the mechanisms via which hepatocellular neoplasms, i.e., hepatocellular adenoma and hepatocellular carcinoma, arise. Hepatocellular carcinoma usually occurs in livers with chronic disease, due to deregulation of important intracellular pathways of signal transmission. Recent studies suggest that subclassification of hepatocellular carcinoma is practically useful. On the other hand, subclassification of hepatocellular adenomas has been well established through correlation of molecular alterations with morphology and protein expression. Advances in hepatic imaging have resulted in a new approach for diagnostic assessment of lesions arising in advanced chronic liver disease. Histologic examination, aided by immunohistochemistry, is the gold standard for the diagnosis and subclassification of hepatocellular neoplasms, while clinicopathologic correlation is essential for best patient management. We summarize the etiology and pathogenesis of hepatocellular neoplasms, provide practical information for their histologic diagnosis, and address various frequently asked questions regarding their diagnosis and practical implications. Hepatocellular carcinoma (HCC), a major global contributor of cancer death, usually arises in a background of chronic liver disease, as a result of molecular changes that deregulate important signal transduction pathways. Recent studies have shown that certain molecular changes of hepatocarcinogenesis are associated with clinicopathologic features and prognosis, suggesting that subclassification of HCC is practically useful. On the other hand, subclassification of hepatocellular adenomas (HCAs), a heterogenous group of neoplasms, has been well established on the basis of genotype–phenotype correlations. Histologic examination, aided by immunohistochemistry, is the gold standard for the diagnosis and subclassification of HCA and HCC, while clinicopathologic correlation is essential for best patient management. Advances in clinico-radio-pathologic correlation have introduced a new approach for the diagnostic assessment of lesions arising in advanced chronic liver disease by imaging (LI-RADS). The rapid expansion of knowledge concerning the molecular pathogenesis of HCC is now starting to produce new therapeutic approaches through precision oncology. This review summarizes the etiology and pathogenesis of HCA and HCC, provides practical information for their histologic diagnosis (including an algorithmic approach), and addresses a variety of frequently asked questions regarding the diagnosis and practical implications of these neoplasms. [ABSTRACT FROM AUTHOR]

Background and Aims: Hepatobiliary phase (HBP) Gd‐EOB‐DTPA‐enhanced magnetic resonance imaging (MRI) has increased the accuracy in differentiating focal nodular hyperplasia (FNH) and hepatocellular adenoma (HCA). However, the ability of this technique to distinguish HCA subtypes remains controversial. The aim of this study was to investigate the expression of hepatocyte transporters (OATPB1/B3, MRP2, MRP3) in HCA subtypes, hence to understand their MRI signal intensity on HBP Gd‐EOB‐DTPA‐enhanced MRI. Methods: By means of immunohistochemistry (IHC), we scored the expression of OATPB1/B3, MRP2 and MRP3, in resected specimens of FNH (n = 40), subtyped HCA (n = 58) and HCA with focal malignant transformation (HCA‐HCC, n = 4). Results were validated on a supplementary set of FNH (n = 6), subtyped HCA (n = 17) and HCA‐HCC (n = 1) with Gd‐EOB‐DTPA MR images. Results: All FNH showed a preserved expression of hepatocytes transporters. Beta‐catenin‐activated HCA (at highest risk of malignant transformation) and HCA‐HCC were characterized by preserved/increased OATPB1/B3 expression (predictor of hyperintensity on HBP), as opposed to other HCA subtypes (P < 0.01) that mostly showed OATPB1/B3 absence (predictor of hypointensity on HBP). HCA‐HCC showed an additional MRP3 overexpressed profile (P < 0.01). On HBP Gd‐EOB‐DTPA‐enhanced MRI, FNH and HCA signal intensity reflected the profile predicted by their specific OATPB1/B3 tissue expression. The hyperintense vs hypointense HBP signal criterion was able to distinguish all higher risk HCA and HCA‐HCC (100% accuracy). Conclusions: OATPB1/B3 and MRP3 IHC and signal intensity on HBP Gd‐EOB‐DTPA‐enhanced MRI can help to stratify HCA according to their risk of malignant transformation. [ABSTRACT FROM AUTHOR]

The identification of hepatocellular adenoma ( HCA) with mutation in exon 3 of the CTNNB1 gene encoding for β-catenin is clinically relevant due to a higher risk of malignant transformation. Inflammatory HCA ( IHCA) can exhibit β-catenin activation (β- IHCA). We report two cases with multiple IHCA in which focal β-catenin activation has been found in one of the IHCA. In both cases, the diagnosis of IHCA was confirmed on the resected nodules by routine stains, immunohistochemical detection of C-reactive protein ( CRP) and molecular biology on frozen material. An additional molecular analysis was performed on formalin-fixed paraffin-embedded ( FFPE) material that showed focal glutamine synthetase ( GS) staining, the surrogate marker of β-catenin activation. In case 1, it was a 1.8-cm area within the 7.5 cm IHCA, and in case 2 a small 0.3-cm area within a 1.8 cm resected IHCA located close to a larger IHCA, negative for GS. In both cases, nuclear β-catenin expression and decreased reticulin network were observed in the GS expressing foci, together with cholestasis and diffuse CD34 expression in case 1. Molecular analysis by pyrosequencing on FFPE material using the GS-stained slides as reference to select areas with/without positive staining revealed a CTNNB1 exon 3 mutation restricted to the areas exhibiting both positive GS and CRP expression, whereas wild-type CTNNB1 was found in areas showing only CRP staining. These two cases illustrate focal β-catenin activation that can occur within IHCAs. Additional data are needed to determine if β-catenin mutation is a secondary event in IHCA. [ABSTRACT FROM AUTHOR]

Aims To report the coexistence of inflammatory hepatocellular adenoma (IHCA) and HNF1α-inactivated HCA ( H- HCA) in cases from a multicentre study. Methods and results We report nine cases with the coexistence of IHCA and H- HCA; eight occurred in women, and one in a man. The numbers of nodules and the sizes of the largest and smallest HCAs were variable. In one case, the nodules of the two different subtypes were discovered at different times. In all women, HCAs were histologically typical, regardless of their subtype, whereas H- HCA in the man differed histologically from classic H- HCA. Conclusions These cases suggest that a predisposition to develop multiple adenomas, hypothetically caused by a 'benign tumorigenic field effect', although common to all HCAs, may result in different genotypes and phenotypes. Although this is rare, it is expected that more cases with the coexistence of different genotypes will emerge, owing to progress in the use of specific immunohistochemical approaches. [ABSTRACT FROM AUTHOR]

Congenital hyperinsulinism causes persistent hypoglycemia in neonates and infants. Most often, uncontrolled insulin secretion (IS) results from a lack of functional KATP channels in all β-cells or only in β-cells within a resectable focal lesion. In more rare cases, without KATP channel mutations, hyperfunctional islets are confined within few lobules, whereas hypofunctional islets are present throughout the pancreas. They also can be cured by selective partial pancreatectomy; however, unlike those with a KATP focal lesion, they show clinical sensitivity to diazoxide. Here, we characterized in vitro IS by fragments of pathological and adjacent normal pancreas from six such cases. Responses of normal pancreas were unremarkable. In pathological region, IS was elevated at 1 mmol/L and was further increased by 15 mmol/L glucose. Diazoxide suppressed IS and tolbutamide antagonized the inhibition. The most conspicuous anomaly was a large stimulation of IS by 1 mmol/L glucose. In five of six cases, immunohistochemistry revealed undue presence of low-Km hexokinase-I in β-cells of hyperfunctional islets only. In one case, an activating mutation of glucokinase (I211F) was found in pathological islets only. Both abnormalities, attributed to somatic genetic events, may account for inappropriate IS at low glucose levels by a subset of β-cells. They represent a novel cause of focal congenital hyperinsulinism. [ABSTRACT FROM AUTHOR]

Summary: Immunohistochemical detection of DNA mismatch repair proteins and polymerase chain reaction detection of microsatellite instability have enhanced the recognition of mismatch repair–deficient neoplasms in patients with Lynch syndrome and, consequently, led to the identification of tumors that have not been included in the currently known Lynch syndrome tumor spectrum. Here, we report 4 such unusual tumors. Three of the 4, a peritoneal mesothelioma, a pancreatic acinar cell carcinoma, and a pancreatic well-differentiated neuroendocrine tumor, represented tumor types that, to the best of our knowledge, have not been previously reported in Lynch syndrome. The fourth tumor was an adrenocortical carcinoma, which has rarely been reported previously in Lynch syndrome. Three of our 4 patients carried a pathogenic germ-line mutation in a mismatch repair gene. The unusual tumor in each of the 3 patients showed loss of the mismatch repair protein corresponding to the mutation. The fourth patient did not have mutation information but had a history of colonic and endometrial carcinomas; both lacked MSH2 and MSH6 proteins. Interestingly, none of the 4 unusual tumors revealed microsatellite instability on polymerase chain reaction testing, whereas an appendiceal carcinoma from 1 of the study patients who was tested simultaneously did. The recognition of such tumors expands the repertoire of usable test samples for the workup of high-risk families. As yet, however, there are no data to support the inclusion of these tumors into general screening guidelines for detecting Lynch syndrome, nor are there data to warrant surveillance for these tumors in patients with Lynch syndrome. [Copyright &y& Elsevier]

Summary: Although evidence suggests an inverse relationship between microsatellite instability and p53 alterations in colorectal cancer, no study has thoroughly examined the use of p53 immunohistochemistry in phenotyping colorectal cancers. We investigated the value of p53 immunohistochemistry in microsatellite instability–positive colorectal cancers prescreening and attempted to clarify the relationship between DNA mismatch repair system and p53 pathway. In a series of 104 consecutive colorectal cancers, we performed p53 immunohistochemistry, TP53 mutational analysis, DNA mismatch repair system efficiency evaluation (DNA mismatch repair system immunohistochemistry, microsatellite instability status, MLH1/MSH2 germ line, and BRAF, murine double minute 2, and p21 immunohistochemistry. Microsatellite instability high was observed in 25 of 104 colorectal cancers, with DNA mismatch repair system protein loss (24/25) and germ line (8/25) or BRAF mutations (8/25). p53 immunohistochemistry revealed 3 distinct patterns of expression: complete negative immunostaining associated with truncating TP53 mutations (P < .0001), diffuse overexpression associated with missense TP53 mutations (P < .0001), and restricted overexpression characterized by a limited number of homogenously scattered strongly positive tumor cells in 36.5% of colorectal cancers. This latest pattern was associated with wild-type TP53 and microsatellite instability high colorectal cancers (P < .0001) including all Lynch tumors (8/8), but its presence among 22% of DNA mismatch repair system–competent colorectal cancers decreased its positive predictive value (55.2% [95% confidence interval, 45%-65%]). It was also correlated with murine double minute 2 overexpression (P < .0001) and inversely with p21 loss (P = .0002), independently of microsatellite instability status. In conclusion, a restricted pattern of p53 overexpression is preferentially associated with microsatellite instability high phenotype and could, therefore, be of clinical use as signal for microsatellite instability analysis in a large-scale tumor screening. Its association with concomitant murine double minute 2 overexpression suggests an alternative mechanism of p53 pathway deregulation. [ABSTRACT FROM AUTHOR]

Cholangiocarcinomas are malignant tumors that derive from cholangiocytes of small intrahepatic bile ducts or bile ductules (intrahepatic cholangiocarcinoma; ICC), or of large hilar or extrahepatic bile ducts (extrahepatic cholangiocarcinoma; ECC). ICC and ECC differ in morphology, pathogenesis, risk factors, treatment, and prognosis. This review focuses on ICC, which is rising in incidence with the emergence of hepatitis C virus (HCV) infection as a risk factor. The authors examined 73 ICC, which were resected at The Mount Sinai Medical Center in New York City, and reviewed the literature. The tumors were categorized into classical and nonclassical ICCs based on histopathology. Classical ICCs (54.8%) were characterized by a tubular, glandular, or nested pattern of growth, were significantly associated with tumor size of more than 5 cm and the absence of underlying liver disease and/or advanced fibrosis. Nonclassical ICCs (45.2%) consisted of tumors with trabecular architecture, tumors that exhibited features of extrahepatic carcinomas, and carcinomas considered to be derived from hepatic progenitor cells, i.e., combined hepatocellular/cholangiocarcinomas and cholangiolocellular carcinomas (ductular type of ICC). They were smaller and often arose in chronic liver disease, mostly HCV infection, and/or with significant fibrosis. The role of immunohistochemistry in the diagnosis of ICC and the importance of the new American Joint Committee on Cancer Staging System for ICC are also discussed. [ABSTRACT FROM AUTHOR]

Characterizes persistent hyperinsulinemic hypoglycemia during infancy. Determination of pancreatic beta-cell proliferation rate; Application of double immunohistochemical technique to detect Ki67 antigen; Implication of the activation of potentially protective genes.

Background & Aims Although hepatitis E constitutes a substantial disease burden worldwide, surprisingly little is known about the localization of hepatitis E virus (HEV) in the human liver. We therefore aimed to visualize HEV RNA and proteins in situ . Methods A panel of 12 different antibodies against HEV open reading frame (ORF) 1–3 proteins was evaluated for immunohistochemistry (IHC) and two probes for in situ hybridization (ISH) in formalin-fixed, paraffin-embedded (FFPE) HuH7 cells transfected with HEV ORF1-3 expression vectors. IHC (and partly ISH) were then applied to Hep293TT cells replicating infectious HEV and liver specimens from patients with hepatitis E (n = 20) and controls (n = 134). Results Whereas ORF1-3 proteins were all detectable in transfected, HEV protein-expressing cells, only ORF2 and 3 proteins were traceable in cells replicating infectious HEV. Only the ORF2-encoded capsid protein was also unequivocally detectable in liver specimens from patients with hepatitis E. IHC for ORF2 protein revealed a patchy expression in individual or grouped hepatocytes, generally stronger in chronic compared to acute hepatitis. Besides cytoplasmic and canalicular, ORF2 protein also displayed a hitherto unknown nuclear localization. Positivity for ORF2 protein in defined areas correlated with HEV RNA detection by ISH. IHC was specific and comparably sensitive as PCR for HEV RNA. Conclusions ORF2 protein can be reliably visualized in the liver of patients with hepatitis E, allowing for sensitive and specific detection of HEV in FFPE samples. Its variable subcellular distribution in individual hepatocytes of the same liver suggests a redistribution of ORF2 protein during infection and interaction with nuclear components. Lay summary The open reading frame (ORF) 2 protein can be used to visualize the hepatitis E virus (HEV) in the human liver. This enabled us to discover a hitherto unknown localization of the HEV ORF2 protein in the nucleus of hepatocytes and to develop a test for rapid histopathologic diagnosis of hepatitis E, the most common cause of acute hepatitis worldwide. [ABSTRACT FROM AUTHOR]