Neural and neurogenic tumours of the gastroenteropancreaticobiliary tract

Neural lesions occur uncommonly in the gastroenteropancreaticobiliary tract. However, due to the growing number of screening colonoscopy procedures, polypoid neural lesions of the colon are being recognised increasingly and range from benign tumours to high-grade malignant neoplasms. Morphological variability of neural tumours can be wide, although some entities share pathological features, and, as such, these lesions can be diagnostically challenging. We review the spectrum of pathology of neural tumours in the gastroenteropancreaticobiliary tract, with the goal of providing a practical approach for practising surgical pathologists.

Tumours composed of fat are no longer a simple diagnosis: an overview of fatty tumours with a spindle cell component

This is a review of the morphological spectrum of fatty tumours containing a component of spindle cells, highlighting the immunohistochemical and cytogenetic workup that is now mandatory for accurate diagnosis, with the goal of providing a practical approach for practising surgical pathologists. There have been significant advances in recent years in classifying and understanding the pathogenesis of fatty tumours with spindle cells, based on the correlation of histological, immunohistochemical and cytogenetic/molecular findings. In spite of this, morphological diagnosis and accurate classification of fatty tumours with spindle cells can be challenging to diagnostic pathologists. A group of three lesions: spindle cell lipoma, mammary-type myofibroblastoma and cellular angiofibroma share morphological features and are united by retinoblastoma protein (pRb) loss. Closely allied to these lesions, especially spindle cell lipoma is the newly designated atypical spindle cell lipomatous tumour, which shares morphological, immunohistochemical and cytogenetic features with the trio of tumours lacking nuclear pRb. All of these lesions lack MDM2 and CDK4 amplification as well and separation is based on clinical features, principally location. Atypical lipomatous tumour or well-differentiated liposarcoma shows retention of pRb but overexpression and amplification of MDM2. Fatty tumours with spindle cells need to be extensively sampled, with careful attention paid to cellular atypia and location, and they need to have immunohistochemical workup with pRb, MDM2, desmin, CD34 and p16. In addition, cytogenetic analysis for MDM2 and CDK4 amplification has become crucial for the proper identification of these lesions.

Rnf43

RNF43 (E3 ubiquitin-protein ligase RNF43 or RING-type E3 ubiquitin transferase RNF43) functions as a tumor suppressor, by exerting a predominant negative feedback mechanism in the Wnt/β-catenin signaling pathway. RNF43 inhibits Wnt/beta-catenin signaling by ubiquitinating Frizzled receptor and targeting it to the lysosomal pathway for degradation. Loss of function of RNF43 results in decrease/lack of degradation of Frizzled with enhancement of Wnt/β-catenin signaling pathway. Mutations of RNF43 have been reported in different cancers. We describe the structure of RNF43, its function and most frequent mutations in different cancers.

Gastric glomus tumor: clinical conundrums and potential mimic of gastrointestinal stromal tumor (GIST)

Gastric glomus tumor is a rare neoplasm of the gastrointestinal tract that frequently mimics other mesenchymal lesions clinically and radiologically. We present a 70-year-old woman with an incidentally detected submucosal tumor of the antrum that was thought to be a gastrointestinal stromal tumor (GIST). The lesion measured 1.9 cm radiographically and was monitored over a period of 3 years. Multiple biopsies were attempted but did not yield a clear diagnosis. Over time, the lesion increased in size and developed an area of ulceration, prompting a wedge resection. After surgery, a diagnosis of glomus tumor was reached on the basis of histological and immunohistochemical studies. Glomus tumors are neoplasms of perivascular smooth muscle differentiation that can occur nearly anywhere in the body but exhibit a strong predisposition for the skin and subcutaneous tissue. They usually follow an indolent clinical course, although rare cases of metastasis have been reported. Gastrointestinal involvement is uncommon, and when present, the stomach is almost exclusively involved. Preoperative diagnosis may be impossible given the overlapping features with other mesenchymal tumors of the stomach, as illustrated in our case. A literature review of 210 gastric glomus tumors is provided, and important diagnostic pitfalls are highlighted to prevent misdiagnosis. In an era of precision medicine where incidental lesions are increasingly detected by routine endoscopy and imaging, awareness of this rare entity is important, as gastric glomus tumors are generally benign with a favorable prognosis following complete resection.

Primary inferior vena cava smooth muscle tumor with diffuse bizarre giant nuclei and low mitotic rate: a nomenclatural conundrum

A male patient with obstructive jaundice was found to have an incidental nodule within the inferior vena cava (IVC), below the level of the renal vein, on abdominal imaging. At the time of the Whipple's procedure for pancreatic adenocarcinoma, the IVC mass measuring 3.4×2.7×2.2 cm was also removed. Histologically, the lesion was well circumscribed, composed focally of spindle-shaped cells with cigar-shaped nuclei reminiscent of smooth muscle and a dominant pervasive, pleomorphic, bizarre giant cell component. Two mitoses per 10 high-power fields were identified in the most mitotically active area of the entire tumor, with the vast majority of the tumor being mitotically inert. Additionally, no evidence of coagulative necrosis was noted. The bizarre giant cells had multi- and polylobated configurations, and several were replete with nuclear pseudoinclusions. Both the spindle cell and pleomorphic components displayed strong immunoreactivity for all smooth muscle markers. This lesion conformed morphologically to a smooth muscle tumor with bizarre nuclei or so-called symplastic/bizarre leiomyoma, as encountered in the uterus. However, current thinking based on location in the IVC and the presence of any mitotic activity with cellular atypia makes this lesion a leiomyosarcoma. Perhaps more pragmatic terminology would be smooth muscle tumor with bizarre nuclei and low malignant potential since the limited number of cases described thus far appear to have a more indolent course.

Mucin-rich variant of traditional serrated adenoma: a distinct morphological variant

AIMS

Traditional serrated adenomas (TSAs) account for 5% of serrated polyps, and have a villiform architecture, eosinophilic cells with a brush border, and indented, flat-topped luminal serrations. However, some are composed of mucin-filled goblet cells (GCs): mucin-rich TSA (MrTSA). The aim of this study was to determine whether this variant has unique features as compared with classic TSA (cTSA).

METHODS AND RESULTS

One hundred and fifty-six TSAs were retrieved from the period 2010-2016. Patient demographics, site of polyps and 16 microscopic variables were evaluated. TSAs containing ≥50% GCs were classified as MrTSAs. Ectopic crypt foci (ECFs) were quantified as low (1-10) or high (>10), counted at ×200 magnification, and the average was taken for 10 fields. Twenty-four fulfilled the criteria for MrTSA. In males, MrTSAs (65%) were more prevalent than cTSAs (55%). There was no age difference, and both variants had a predilection for the left colon, although, in the right colon, MrTSAs were more frequent (39%) than cTSAs (10%) (P = 0.012). Adenomatous dysplasia was present in four of 24 MrTSAs (low grade, 3; high grade, 1). The most distinctive features of MrTSAs were: a variable growth pattern [endophytic (9%), mixed (30%), or villiform/exophytic (61%)], and a lower frequency of ECFs (P = 0.001) and more intraepithelial lymphocytes (P < 0.05) than in cTSAs. MrTSAs retain characteristic luminal serrations, at least focally. Inflamed MrTSAs can mimic inflammatory polyps and hamartomatous polyps (when there are >95% GCs).

CONCLUSIONS

MrTSA is characterized by >50% GCs, and fewer ECFs than cTSA, but with preservation of archetypal luminal serrations. Awareness of this variant will prevent misdiagnosis, given the association of TSA with the accelerated pathway to colorectal cancer.

Gastric foveolar dysplasia: a survey of reporting habits and diagnostic criteria

This study aimed to ascertain views, incidence of reporting and diagnostic criteria for gastric foveolar dysplasia. A questionnaire, a post-questionnaire discussion and microscopic assessment of selected cases was conducted by gastrointestinal pathologists to explore the above-stated aims. Fifty-four percent of respondents never or rarely diagnosed gastric foveolar-type dysplasia. The general consensus was that round nuclei, lack of nuclear stratification, presence of inflammation/damage and surface maturation favoured reactive change; while architectural abnormalities/complexity and nuclear enlargement mainly were used to separate low-grade from high-grade foveolar dysplasia. Immunohistochemistry was rarely used to make the diagnosis of dysplasia and was thought not to be of help in routine practice. Inter-observer agreement in grading of dysplasia versus reactive, and the type of dysplasia (foveolar versus adenomatous), was substantial/almost perfect amongst 35.7% and 21.4% of participants, respectively. This reflects low reproducibility in making these diagnoses. In conclusion, foveolar dysplasia was a rarely made diagnosis among 14 gastrointestinal pathologists, there are no uniform criteria for diagnosis and there is poor inter-observer agreement in separating low-grade foveolar dysplasia from reactive gastric mucosa and low-grade adenomatous dysplasia. Greater awareness and agreed criteria will prevent misdiagnosis of low-grade foveolar dysplasia as reactive, and vice versa.

An unusual primary malignant tumor of the stomach: fetal gutlike gastric adenocarcinoma with "blastoma"-like component

An unusual case of a polypoid, malignant gastric tumor in a 62-year-old man is presented. Endoscopy and subsequent polypectomy revealed an 8.5 × 6.5 × 4.5-cm lesion in the body of the stomach. Microscopy showed surface dysplasia with an invasive adenocarcinoma displaying prominent tubulopapillary areas composed of large vacuolated cells, pleomorphic nuclei, and occasional cytoplasmic hyaline globules. This component then blended with tubular structures lined by more primitive-appearing vacuolated cells embedded within a stroma made up of cellular primitive, high-grade blastemalike areas and less cellular, more pleomorphic foci with spindle and several bizarre, large cells. Immunohistochemistry showed the adenocarcinoma and primitive tubules to be strongly SALL4 and epithelial marker positive but with only focal expression of α-fetoprotein and glypican-3. The stromal component made up of blastemalike areas displayed strong immunoreactivity for glypican-3. The pleomorphic stromal areas were negative for all markers, including epithelial and muscle markers. The overall morphology and expression of primitive oncofetal proteins, especially SALL4 and glypican-3, are in keeping with this being a primitive adenocarcinoma showing fetal gutlike differentiation with an accompanying blastomalike component, a combination not previously described in a primary gastric cancer.

Epstein-Barr Virus-Associated Smooth Muscle Tumor

Immunodeficient individuals are prone to develop a number of opportunistic infections and unique neoplasms. Epstein-Barr virus-associated smooth muscle tumor is an uncommon neoplasm associated with immunodeficiency. It has been described in patients infected with human immunodeficiency virus, in the posttransplant setting, and in those with congenital immunodeficiency. Different anatomic sites can be involved by Epstein-Barr virus-associated smooth muscle tumor, and even multiple locations can contain these unique lesions within the same patient. The presence of variable numbers of intratumoral lymphocytes and primitive round cell areas are the unique defining features for this tumor. Histopathologic features may vary considerably in terms of cellular atypia, mitotic activity, and necrosis, with no correlation to the clinical behavior. Demonstration of Epstein-Barr virus infection by in situ hybridization within tumor cell remains critical for the diagnosis. The mechanism for Epstein-Barr virus infection of progenitor cells and neoplastic transformation has been an area of interest and conjecture. Different treatment strategies are proposed according to underlying disease status. This paper reviews the clinicopathologic features of this uncommon neoplasm with detailed discussion of the role of Epstein-Barr virus in the pathogenesis.

A pragmatic approach to vasculitis in the gastrointestinal tract

Although vasculitis involving the gastrointestinal tract (GIT) is an uncommon occurrence, occasionally vasculitis can present as haemorrhagic infarction or ischaemia for which a length of bowel is removed. Invariably, the appropriate clinical history is not forthcoming, or vasculitis is not clinically suspected. The purpose of this overview is to provide the practising gastrointestinal (GI) pathologist with a framework to recognise and diagnose vasculitides within the GIT. The classification may be approached by aetiological agent or size of vessel involved; an international consensus group now favours the latter approach. The symptoms that systemic and/or localised vasculitis may cause in the GIT are protean and non-specific. As a result, pathologists examining resection specimens for unexplained haemorrhagic infarction or ischaemia should be aware that vasculitis may be a potential cause. Several well-known systemic vasculitides such as polyarteritis nodosa, microscopic polyangiitis, eosinophilic granulomatosis with polyangiitis or Churg-Strauss syndrome and granulomatosis with polyangiitis or Wegener's granulomatosis can occur in the GIT. The latter three constitute the antineutrophil cytoplasmic antibody-positive vasculitides. In addition, the so-called solitary organ vasculitis (SOV) can occur in the GIT as the harbinger of later onset systemic vasculitis, and be the cause of the GIT symptoms. In addition, SOV can occur incidentally and coexist with GIT disease such as gallstones or polyps, and there may be no manifestations of systemic vasculitis for years, or not at all.

From traditional serrated adenoma to tubulovillous adenoma and beyond

It is well established that colorectal cancer develops from a series of precursor epithelial polyps, including tubular adenomas, villous/tubulovillous adenomas (VA/TVA), sessile serrated adenomas (SSA) and traditional serrated adenomas (TSA). Of these, TSAs are least common and account for only 5% of all serrated polyps. TSAs are characterised by the presence of a “pinecone-like” architecture, granular eosinophilic cytoplasm, luminal serrations, ectopic crypt foci (ECF) and elongated, pencillate nuclei. However, the distinct slit-like luminal serrations, reminiscent of small bowel mucosa, appear to be the most unique and reproducible feature to distinguish TSAs from other polyps. There is a contention that TSAs are not inherently dysplastic and that the majority do not show cytological atypia. Two types of dysplasia are associated with TSA. Serrated dysplasia is less well recognised and less commonly encountered than adenomatous dysplasia. In addition, it is now becoming increasingly evident that TSAs can be admixed with HP, SSA and VA/TVA. At a genetic level, polyps may switch phenotype as they accumulate genetic changes, evolving from a serrated pathway to a more conventional one, which could be the basis for a spectrum theory starting out with a TSA with serration and ECF evolving into a TSA with conventional dysplasia and, eventually, to a well-developed conventional adenoma. Nevertheless, there is an exigency for future studies to provide further illumination and bridge the gaps in our present understanding.

Regression grading in neoadjuvant treated pancreatic cancer: an interobserver study

AIM

Several regression grading systems have been proposed for neoadjuvant chemoradiation-treated pancreatic ductal adenocarcinoma (PDAC). This study aimed to examine the utility, reproducibility and level of concordance of three most frequently used grading systems.

METHODS

Four gastrointestinal pathologists used the College of American Pathologists (CAP), Evans, MD Anderson Cancer Centre (MDA) regression grading systems to grade 14 selected cases (7-20 slides from each case) of neoadjuvant chemoradiation-treated PDAC. A postscoring discussion with each pathologist was conducted. The results were entered into a standardised data collection form and statistical analyses were performed.

RESULTS

There was little concordance across the three systems. The Kendall coefficient of concordance agreement scores were: CAP: 2-poor, 2-fair; Evans: 1-fair, 1-moderate, 2-good; MDA: 1-poor, 2-moderate, 1-good. Interpretation in all three grades in the CAP grading system was a source of discrepancy. Furthermore, using fibrosis as a criterion to assess regression was contentious. In the Evans system, quantifying tumour destruction using arbitrary percentage cut-offs (ie, 9% vs 10%; 50% vs 51%, etc) was imprecise and subjective. Although the MDA system generated greatest concordance, this was due to 'oversimplification' surrounding wide, arbitrarily assigned thresholds of </> 5% of tumour.

CONCLUSIONS

All systems lacked precision and clarity for accurate regression grading. Presently the clinical utility and impact of histological regression grading in patient management is questionable. There is a need to re-evaluate regression grading in the pancreas and establish a reproducible, clinically relevant grading system.

Wnt disruption in colorectal polyps - the traditional serrated adenoma enters the fray

The adenoma-carcinoma sequence describes the development of colorectal carcinoma (CRC) from benign colorectal precursor lesions. Molecular classification of established CRC has demonstrated considerable disease heterogeneity; however, as an emerging cancer frequently outgrows and destroys the initial precursor lesion, CRC molecular taxonomy can only be partially reconciled with histologically classified polyps. Thus, the molecular pathogenesis of some colorectal polyp types, including the traditional serrated adenoma (TSA), is still unclear. Now, candidate driver gene analysis of a cohort of different polyps reveals characteristic, but highly variable, mutations disrupting the Wnt signalling pathway across different histological polyp subtypes. How and when different precursor lesions acquire Wnt disruption reflects important distinctions in polyp biology, dependent on a combination of the dominant molecular pathway and the cell of origin of individual lesions. TSAs preferentially acquire ligand-dependent Wnt activating mutations, which means that the cancers that arise from these aggressive polyps may be sensitive to targeted Wnt inhibition. This paper demonstrates that applying next-generation sequencing technology to improve our understanding of colorectal precursor lesion molecular pathogenesis could also give important and translationally relevant insights into colorectal cancer biology. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.