Expression of Markers of Hepatocellular Differentiation in Pancreatic Acinar Cell Neoplasms: A Potential Diagnostic Pitfall

A narrative review on rare types of pancreatic cancer: should they be treated as pancreatic ductal adenocarcinomas?

Pancreatic cancer is one of the deadliest malignancies in humans and it is expected to play a bigger part in cancer burden in the years to come. Pancreatic ductal adenocarcinoma (PDAC) represents 85% of all primary pancreatic malignancies. Recently, much attention has been given to PDAC, with significant advances in the understanding of the mechanisms underpinning disease initiation and progression, along with noticeable improvements in overall survival in both localized and metastatic settings. However, given their rarity, rare histological subtypes of pancreatic cancer have been underappreciated and are frequently treated as PDAC, even though they might present non-overlapping molecular alterations and clinical behavior. While some of these rare histological subtypes are true variants of PDAC that should be treated likewise, others represent separate clinicopathological entities, warranting a different therapeutic approach. In this review, we highlight clinical, pathological, and molecular aspects of rare histological types of pancreatic cancer, along with the currently available data to guide treatment decisions.

Focal Hepatocellular Carcinoma in Pancreas

A 67-year-old man was found to have a pancreatic head mass on abdominal ultrasound. He had compensated liver cirrhosis due to hepatitis C. The fine-needle aspiration (FNA) biopsy of the mass reported an adenocarcinoma of the pancreas, while the subsequent histopathology report of the supraclavicular lymph node showed features of hepatocellular carcinoma (HCC). A second read and additional stains on the FNA specimen confirmed a hepatoid (hepatocellular) carcinoma of the pancreas. He received atezolizumab and bevacizumab and had a good response. Tumors with features of HCC outside of the liver rarely occur and even more rarely in pancreas, with less than 50 cases reported so far. Pure HCC-like morphology is the most common histological form among four subtypes and has a relatively better prognosis. Surgical resection is considered the treatment of choice if amenable and variable outcomes are reported with different chemotherapies. Challenges exist in the diagnosis and the management of this rare and intriguing entity, and the potential misdiagnosis can have grave consequences as the management is completely different for a pancreatic adenocarcinoma and hepatoid carcinoma. We report a case with a challenging diagnosis of metastatic pancreatic hepatoid carcinoma which was treated as unresectable HCC with immunotherapy and the patient had a good response.

An Update on the Role of Immunohistochemistry in the Evaluation of Pancreatic/Liver/Gastrointestinal Luminal Tract Disorders

CONTEXT.—

Immunohistochemistry serves as an ancillary diagnostic tool for a wide variety of neoplastic and nonneoplastic disorders, including infections, workup of inflammatory conditions, and subtyping neoplasms of the pancreas/liver/gastrointestinal luminal tract. In addition, immunohistochemistry is also used to detect a variety of prognostic and predictive molecular biomarkers for carcinomas of the pancreas, liver, and gastrointestinal luminal tract.

OBJECTIVE.—

To highlight an update on the role of immunohistochemistry in the evaluation of pancreatic/liver/gastrointestinal luminal tract disorders.

DATA SOURCES.—

Literature review and authors' research data and personal practice experience were used.

CONCLUSIONS.—

Immunohistochemistry is a valuable tool, assisting in the diagnosis of problematic tumors and benign lesions of the pancreas, liver, and gastrointestinal luminal tract, and also in the prediction of prognosis and therapeutic response for carcinomas of the pancreas, liver, and gastrointestinal luminal tract.

Ancillary tests for hepatobiliary neoplasms: what we know and what we need to know

Ancillary tests are commonly used in the surgical pathology setting for diagnosing challenging neoplastic diseases of the liver and biliary tract, while histology and clinical correlation remain to be critically important. With continuous discoveries, more and more useful ancillary tests have become available, which can help distinguish between malignant and benign hepatocellular neoplasms, malignant and benign biliary tract entities, and intrahepatic and metastatic carcinomas. This review will focus on existing and emerging biomarkers (such as glutamine synthetase, organic anion transporting polypeptide 1B3, insulin-like growth factor-II mRNA binding protein-3, S100P, SMAD4, enhancer of zeste homolog 2, albumin, hepatocyte nuclear factor-1β, etc.) that can be used for the diagnosis, classification and prognostication of hepatobiliary neoplasms.

Solid-Tubulocystic carcinoma: A new variant of intrahepatic cholangiocarcinoma

A new variant of intrahepatic cholangiocarcinoma (iCCA) has been recognized in recent years presenting predominantly as a large hepatic mass in young woman with the characteristic expression of inhibin by immunohistochemistry. This variant iCCA was originally termed as cholangioblastic variant of iCCA, and subsequently proposed to be renamed as inhibin-positive hepatic carcinoma or solid-tubulocystic variant of iCCA to better reflect its immunohistochemical profile or morphologic spectrum. The tumor histologically is composed of small to medium sized cells with scant to moderate amount of eosinophilic cytoplasm heterogeneously organized in solid, tubular, and cystic growth patterns. The tumor cells are positive for biliary markers, inhibin and albumin, and have a novel recurrent gene fusion, NIPBL::NACC1. Awareness of this new iCCA variant and its clinicopathologic features will aid in the diagnostic work-up and avoid confusion with other primary and metastatic hepatic neoplasms.

[Rare pancreatic tumors]

Beyond pancreatic ductal adenocarcinoma, which is by far the most frequent pancreatic neoplasm, a great variety of tumors occur in the pancreas. They include solid and cystic masses and epithelial and nonepithelial neoplasms, and they show a great diversity in their biological behavior, ranging from benign tumors to highly aggressive neoplasms. As examples of rare pancreatic tumors, clinical, morphological, and molecular aspects of acinar cell carcinoma, pancreatoblastoma, solid pseudopapillary neoplasm, and serous cystic neoplasms are presented and discussed.

Utility and Limitations of Albumin mRNA In Situ Hybridization Detection in the Diagnosis of Hepatobiliary Lesions and Metastatic Carcinoma to the Liver

Albumin messenger RNA (mRNA) in situ hybridization is a sensitive and specific biomarker for hepatocellular carcinoma (HCC). Intrahepatic cholangiocarcinoma (ICC) shows variable sensitivity, whereas extrahepatic cholangiocarcinoma (ECC) and metastatic carcinoma are generally negative. We studied the clinical utility and limitations of albumin mRNA detection in a cohort of HCCs, ICCs, ECCs, bile duct adenomas, bile duct hamartomas, and metastatic carcinomas to the liver; and investigated the variability in sensitivity observed for this biomarker in ICCs. We identified 122 cases of hepatobiliary lesions and metastatic carcinomas. Albumin mRNA detection was performed using RNAscope run on formalin-fixed, paraffin-embedded tissue sections. ICCs were categorized according to the classification proposed by Hayashi and colleagues into the small duct, large duct, and indeterminate subtypes. Albumin mRNA was detected in all 17 HCCs and focally in 6/8 (75%) of bile duct adenomas. All 28 nonhepatic carcinomas, 13 bile duct hamartomas, and 9 ECCs were negative. Albumin mRNA was found in 38/47 (80.9%) of ICC with 35/37 (94.6%) in the small duct subtype, 2/3 (66.7%) in the indeterminate subtype, and 1/7 (14.3%) of the large duct subtype (P<0.003). Albumin mRNA detection is a sensitive and specific biomarker for HCCs. It is highly sensitive and moderately specific in the diagnosis of ICC with small gland morphology, but not ICCs with large duct morphology and in metastatic carcinoma. The variability in the sensitivity of albumin mRNA expression in ICCs may depend on the subtypes of ICC.

DNAJB1-PRKACA fusions occur in oncocytic pancreatic and biliary neoplasms and are not specific for fibrolamellar hepatocellular carcinoma

Recently discovered DNAJB1-PRKACA oncogenic fusions have been considered diagnostic for fibrolamellar hepatocellular carcinoma. In this study, we describe six pancreatobiliary neoplasms with PRKACA fusions, five of which harbor the DNAJB1-PRKACA fusion. All neoplasms were subjected to a hybridization capture-based next-generation sequencing assay (MSK-IMPACT), which enables the identification of sequence mutations, copy number alterations, and selected structural rearrangements involving ≥410 genes (n = 6) and/or to a custom targeted, RNA-based panel (MSK-Fusion) that utilizes Archer Anchored Multiplex PCR technology and next-generation sequencing to detect gene fusions in 62 genes (n = 2). Selected neoplasms also underwent FISH analysis, albumin mRNA in-situ hybridization, and arginase-1 immunohistochemical labeling (n = 3). Five neoplasms were pancreatic, and one arose in the intrahepatic bile ducts. All revealed at least focal oncocytic morphology: three cases were diagnosed as intraductal oncocytic papillary neoplasms, and three as intraductal papillary mucinous neoplasms with mixed oncocytic and pancreatobiliary or gastric features. Four cases had an invasive carcinoma component composed of oncocytic cells. Five cases revealed DNAJB1-PRKACA fusions and one revealed an ATP1B1-PRKACA fusion. None of the cases tested were positive for albumin or arginase-1. Our data prove that DNAJB1-PRKACA fusion is neither exclusive nor diagnostic for fibrolamellar hepatocellular carcinoma, and caution should be exercised in diagnosing liver tumors with DNAJB1-PRKACA fusions as fibrolamellar hepatocellular carcinoma, particularly if a pancreatic lesion is present. Moreover, considering DNAJB1-PRKACA fusions lead to upregulated protein kinase activity and that this upregulated protein kinase activity has a significant role in tumorigenesis of fibrolamellar hepatocellular carcinoma, protein kinase inhibition could have therapeutic potential in the treatment of these pancreatobiliary neoplasms as well, once a suitable drug is developed.

CHETAH: a selective, hierarchical cell type identification method for single-cell RNA sequencing

Cell type identification is essential for single-cell RNA sequencing (scRNA-seq) studies, currently transforming the life sciences. CHETAH (CHaracterization of cEll Types Aided by Hierarchical classification) is an accurate cell type identification algorithm that is rapid and selective, including the possibility of intermediate or unassigned categories. Evidence for assignment is based on a classification tree of previously available scRNA-seq reference data and includes a confidence score based on the variance in gene expression per cell type. For cell types represented in the reference data, CHETAH’s accuracy is as good as existing methods. Its specificity is superior when cells of an unknown type are encountered, such as malignant cells in tumor samples which it pinpoints as intermediate or unassigned. Although designed for tumor samples in particular, the use of unassigned and intermediate types is also valuable in other exploratory studies. This is exemplified in pancreas datasets where CHETAH highlights cell populations not well represented in the reference dataset, including cells with profiles that lie on a continuum between that of acinar and ductal cell types. Having the possibility of unassigned and intermediate cell types is pivotal for preventing misclassification and can yield important biological information for previously unexplored tissues.

Cholangiolar pattern and albumin in situ hybridisation enable a diagnosis of intrahepatic cholangiocarcinoma

AIMS

The histological distinction of intrahepatic cholangiocarcinoma (ICC) from metastatic adenocarcinoma remains a challenge. The primary goal was to evaluate the diagnostic value of morphology and albumin expression in the diagnosis of ICC.

METHODS

We evaluated morphological patterns in 120 ICCs and 677 non-hepatic adenocarcinomas and performed in situ hybridisation (ISH) stain for albumin in the former cohort (retrospective cohort). We also identified 119 samples from primary and metastatic lesions, the validation cohort, in which albumin ISH was performed as part of the diagnostic workup. Targeted sequencing was performed on selected cases. We also mined existing expression profiling data including cases from The Cancer Genome Atlas (TCGA) (41 760 unique samples).

RESULTS

In the retrospective cohort, 45% of ICCs and <1% of non-hepatic adenocarcinomas showed a cholangiolar pattern; albumin ISH was positive in 93% of ICCs with significant intratumorous heterogeneity. In the validation cohort, 29% of ICCs showed a cholangiolar pattern and 88% expressed albumin, while all metastatic non-hepatic neoplasms were negative (n=37) (sensitivity 88% and specificity 100%). Targetable genetic alterations (IDH mutations and FGFR2 fusions) were identified in 31% of ICCs (10 of 32). An analysis of the TCGA data validated the specificity of the albumin assay.

CONCLUSIONS

The cholangiolar pattern and albumin RNA ISH distinguishes ICC from metastatic adenocarcinoma with high specificity. Given the high prevalence of targetable mutations in ICC, albumin RNA ISH is an essential component in the workup of tumours of uncertain origin. A specific diagnosis of ICC could trigger molecular testing and uncover targetable genetic alterations.

Albumin In Situ Hybridization Can Be Positive in Adenocarcinomas and Other Tumors From Diverse Sites

OBJECTIVES

Albumin messenger RNA (mRNA) expression is a marker of hepatocellular differentiation. Most published data are from review of tissue microarrays, and albumin in situ hybridization (ISH) expression across several tumor types is incompletely characterized.

METHODS

Sections from 221 tumors were evaluated for albumin mRNA. Immunohistochemistry was used to confirm diagnoses. Albumin ISH was performed according to manufacturer-provided instructions. Fifty-nine cases were evaluated with both commercial ISH assays.

RESULTS

Albumin mRNA was detected in all hepatocellular carcinomas (HCCs) and 81% of intrahepatic cholangiocarcinomas. Lung (20%), gallbladder (39%), hepatoid pancreatic (n = 1 of 1) adenocarcinoma, breast invasive ductal carcinoma (18%), yolk sac tumor (25%), and acinar cell carcinoma (29%) showed expression. Both assays were concordant in 93% of cases.

CONCLUSIONS

Albumin ISH was expressed in all HCCs studied. It was also positive in intrahepatic cholangiocarcinoma and patchy positive in gallbladder adenocarcinoma and a subset of other neoplasms, which can be a potential pitfall.

Lipase hypersecretion syndrome: A distinct form of paraneoplastic syndrome specific to pancreatic acinar carcinomas

Lipase hypersecretion syndrome (LHS) is a paraneoplastic syndrome seen exclusively as a result of pancreatic acinar cell carcinoma (ACC). In LHS, acinar enzymes (lipase, trypsin and chymotrypsin) which are normally secreted to the duodenum for digestive purposes, are instead released to the blood by the carcinoma cells. In a way, it is "endocrine-ization" of an "exocrine" function. These circulating enzymes, especially lipase, exerts its digestive action on other tissues, especially on the subcutaneous tissues in the pressure poins of legs, creating a picture often mistaken as erythema nodosum or rheumatic nodules. The bone and joints may also be effected, which mostly appears to be secondary to the complications and super-infection of the skin lesions. Eosinophilia also often accompanies this syndrome. The accurate diagnosis of LHS requires the identification of the pancreatic primary as well as its correct classification as acinar because a variety of pancreatic tumors can be associated with skin lesions, ranging from rare metastasis of adenocarcinoma to the necrolytic migratory erythema caused by glucagon-producing neuroendocrine tumors. Towards this differential, the diagnostic characteristics of acinar cell carcinomas that have been better elucidated in the past decade often need to be employed in increasingly smaller specimens and the liver, especially since most LHS cases also have liver metastasis (presumably due to the by-pass of the "first-pass" liver metabolism phenomenon). ACC (and LHS) occur in patients in their 60's. The pancreatic mass is often large, round, demarcated and closely resemble neuroendocrine and solid-pseudopapillary neoplasms but are more atypical/proliferative, and commonly show single prominent nucleoli and a distinctive chromophilia. Immunostaining with trypsin/chymotrypsin, negativity of beta-catenin help in the differential; as a caveat, neuroendocrine differentiation is common in ACCs. In conclusion, LHS is a rare type of paraneoplastic syndrome specific to ACC. The accurate diagnosis requires attention to their subtle diagnostic characteristics.

Primary Hepatoid Carcinoma of the Pancreas: A Clinicopathological Study of 3 Cases With Review of Additional 31 Cases in the Literature

Primary pancreatic hepatoid carcinoma (PHC) is very rare. Here, we reported 3 such cases with review of additional 31 cases in the literature. Our 3 patients were male (83, 72, and 54 years old, respectively). Serum α-fetoprotein (AFP) was elevated in 1 patient (case 3, 8338 ng/mL) and not measured in the other two. The PHC in patient 1 (pathological stage pT2N0M0) and patient 2 (pT3N0M0) showed pure hepatocellular carcinoma (HCC)-like morphology, whereas in case 3 it was a PHC with true glandular differentiation (pT4N0M0). The diagnosis of PHC was confirmed with positive immunohistochemical staining in the tumor cells for AFP (2/3), Hep Par 1 (3/3), glypican-3 (2/3), arginase-1 (2/3), and Sal-like protein 4 (1/3). CD10 and polyclonal carcinoembryonic antigen stains show focal canalicular pattern in 2/3 tumors. Patient 1 did not receive further treatment after resection and was alive with no evidence of disease at 107 months. Patient 2 died of postoperative complications, whereas patient 3 received postsurgical chemoradiation and died of disease at 29 months. Our findings and literature review indicate that PHCs can be divided into 4 histological subtypes: with pure HCC-like morphology (n = 22), with neuroendocrine differentiation (n = 8), with true glandular differentiation (n = 3), and with acinar cell differentiation (n = 1). On univariate analysis, pure HCC-like morphology was associated with better disease-specific survival (DSS; P = .04), whereas lymph node and distant metastases were associated with worse DSS ( P = .002 for both). Age, gender, presenting symptoms, serum AFP level, and T stage were not associated with DSS. On multivariate analysis, none of these parameters was significantly associated with DSS.

Detection of Albumin Expression by RNA In Situ Hybridization Is a Sensitive and Specific Method for Identification of Hepatocellular Carcinomas and Intrahepatic Cholangiocarcinomas

OBJECTIVES

Inconsistent data on detection of albumin expression by ribonucleic acid (RNA) in situ hybridization have been reported. We investigated the utility of RNAscope (Advanced Cell Diagnostics, Hayward, CA) in detection of albumin in hepatocellular carcinomas (HCCs), intrahepatic cholangiocarcinomas (ICCs), and carcinomas from various organs using manual and automated staining.

METHODS

RNAscope for albumin detection was performed on 482 cases on tissue microarray sections and on 22 cases of ICC, including 14 surgical resection and eight core biopsy specimens.

RESULTS

Thirty-six of 37 (97%) HCCs had detectable mRNA, whereas all non-HCC and non-ICC cases, except one lung adenocarcinoma, were negative for albumin. Fourteen of 22 ICCs (64%) were positive for albumin.

CONCLUSIONS

RNAscope for albumin is highly sensitive and specific for identifying HCCs and is highly specific and moderately sensitive for detection of ICCs; however, rare carcinomas (non-HCC, non-ICC, and those with no hepatoid histomorphology) can also have aberrant expression of albumin.

Update on Ancillary Testing in the Evaluation of High-Grade Liver Tumors

Tissue diagnosis is the gold standard for mass lesions of the liver, but needle core biopsies may sometimes prove challenging. Presented here is a review of a panel of immunohistochemical stains, including hepatocyte in paraffin 1, arginase-1, polyclonal carcinoembryonic antigen, CD10, bile salt export pump, glypican-3, as well as in situ hybridization for albumin RNA, to establish hepatocellular origin in cases in which hepatocellular carcinoma is suspected but the sample is limited or the morphology is challenging, as it may be with cases of scirrhous, fibrolamellar carcinoma, intrahepatic cholangiocarcinoma, and combined hepatocellular-cholangiocarcinoma.

Practical Immunohistochemistry in Neoplastic Pathology of the Gastrointestinal Tract, Liver, Biliary Tract, and Pancreas

CONTEXT

- Immunomarkers with diagnostic, therapeutic, or prognostic values have been increasingly used to maximize the benefits of clinical management of patients with neoplastic diseases of the gastrointestinal tract, liver, biliary tract, and pancreas.

OBJECTIVES

- To review the characteristics of immunomarkers that are commonly used in surgical pathology practice for neoplasms of the gastrointestinal tract, liver, biliary tract, and pancreas, and to summarize the clinical usefulness of immunomarkers that have been discovered in recent years in these fields.

DATA SOURCES

- Data sources include literature review, authors' research data, and personal practice experience.

CONCLUSIONS

- Immunohistochemistry is an indispensable tool for the accurate diagnosis of neoplastic diseases of the gastrointestinal tract, liver, biliary tract, and pancreas. Useful immunomarkers are available to help distinguish malignant neoplasms from benign conditions, determine organ origins, and subclassify neoplasms that are morphologically and biologically heterogeneous. Specific immunomarkers are also available to help guide patient treatment and assess disease aggressiveness, which are keys to the success of personalized medicine. Pathologists will continue to play a critical role in the discovery, validation, and application of new biomarkers, which will ultimately improve patient care.