Histologic Manifestations of Gastrointestinal Adenovirus Infection After Stem Cell Transplant

Adenovirus can cause severe disease in hematopoietic stem cell transplant (HSCT) patients. Histopathologic features of this infection in gastrointestinal biopsies and their distinction from graft-versus-host disease (GVHD) have been incompletely studied. We retrospectively identified patients with gastrointestinal adenovirus infection. H&E-stained sections were reviewed and the histologic features were recorded. The extent of immunostaining was determined using a semiquantitative scale and a maximum number of positive cells per high-power field. Information regarding the clinical course and endoscopic findings were obtained from the electronic medical records. The study group included 32 HSCT patients. Most (81%) presented with diarrhea and detectable virus in the serum. Twenty patients had multiorgan involvement in the gastrointestinal tract, mostly in the duodenum (62%) and colon (56%). Characteristic features included apoptotic epithelial cells with nuclear disarray (84%) and tufted aggregates of degenerating epithelial cells (69%), the latter of which was more commonly seen in the study population more than a control group of HSCT patients with GI involvement by GVHD. Viral inclusions were limited to the superficial epithelium in 59% of samples, and the density of viral inclusions within biopsies was variable (grade 1: 40%, grade 2: 38%, and grade 3: 22%). Following therapy, 10 patients (30%) improved and 14 (42%) had progressive disease. Patients with disease progression were often older (64 vs. 36 years, P =0.01) with higher serologic viral loads, prior history of GVHD, multifocal involvement, and increased number and density of immunoreactive nuclei. Adenovirus infection elicits a spectrum of histologic changes that can simulate or occur in combination with gastrointestinal GVHD. Patients with progressive disease are more likely to have high viral loads and more extensive infection of the gastrointestinal tract.

NIPBL::NACC1 Fusion Hepatic Carcinoma

Several reports describing a rare primary liver tumor with histologic features reminiscent of follicular thyroid neoplasms have been published under a variety of descriptive terms including thyroid-like, solid tubulocystic, and cholangioblastic cholangiocarcinoma. Although these tumors are considered to represent histologic variants, they lack classic features of cholangiocarcinoma and have unique characteristics, namely immunoreactivity for inhibin and NIPBL::NACC1 fusions. The purpose of this study is to present clinicopathologic and molecular data for a large series of these tumors to better understand their pathogenesis. We identified 11 hepatic tumors with these features. Immunohistochemical and NACC1 and NIPBL fluorescence in situ hybridization assays were performed on all cases. Four cases had available material for whole-genome sequencing (WGS) analysis. Most patients were adult women (mean age: 42 y) who presented with abdominal pain and large hepatic masses (mean size: 14 cm). Ten patients had no known liver disease. Of the patients with follow-up information, 3/9 (33%) pursued aggressive behavior. All tumors were composed of bland cuboidal cells with follicular and solid/trabecular growth patterns in various combinations, were immunoreactive for inhibin, showed albumin mRNA by in situ hybridization, and harbored the NIPBL::NACC1 fusion by fluorescence in situ hybridization. WGS corroborated the presence of the fusion in all 4 tested cases, high tumor mutational burden in 2 cases, and over 30 structural variants per case in 3 sequenced tumors. The cases lacked mutations typical of conventional intrahepatic cholangiocarcinoma. In this report, we describe the largest series of primary inhibin-positive hepatic neoplasms harboring a NIPBL::NACC1 fusion and the first WGS analysis of these tumors. We propose to name this neoplasm NIPBL:NACC1 fusion hepatic carcinoma.

A reversible epigenetic memory of inflammatory injury controls lineage plasticity and tumor initiation in the mouse pancreas

Inflammation is essential to the disruption of tissue homeostasis and can destabilize the identity of lineage-committed epithelial cells. Here, we employ lineage-traced mouse models, single-cell transcriptomic and chromatin analyses, and CUT&TAG to identify an epigenetic memory of inflammatory injury in the pancreatic acinar cell compartment. Despite resolution of pancreatitis, our data show that acinar cells fail to return to their molecular baseline, with retention of elevated chromatin accessibility and H3K4me1 at metaplasia genes, such that memory represents an incomplete cell fate decision. In vivo, we find this epigenetic memory controls lineage plasticity, with diminished metaplasia in response to a second insult but increased tumorigenesis with an oncogenic Kras mutation. The lowered threshold for oncogenic transformation, in turn, can be restored by blockade of MAPK signaling. Together, we define the chromatin dynamics, molecular encoding, and recall of a prolonged epigenetic memory of inflammatory injury that impacts future responses but remains reversible.

Tumoral Intraductal Neoplasms of the Bile Ducts Comprise Morphologically and Genetically Distinct Entities

CONTEXT.—

Tumoral (grossly visible) intraductal neoplasms of the bile ducts are still being characterized.

OBJECTIVE.—

To investigate their morphologic, immunohistochemical, and molecular features.

DESIGN.—

Forty-one cases were classified as gastric-, intestinal-, pancreatobiliary-type intraductal papillary neoplasm (IPN), intraductal oncocytic papillary neoplasm (IOPN), or intraductal tubulopapillary neoplasm (ITPN) on the basis of histology. All neoplasms were subjected to targeted next-generation sequencing.

RESULTS.—

The mean age at diagnosis was 69 years (42-81 years); male to female ratio was 1.3. Most neoplasms (n = 23, 56%) were extrahepatic/large (mean size, 4.6 cm). The majority (n = 32, 78%) contained high-grade dysplasia, and 68% (n = 28) revealed invasion. All gastric-type IPNs (n = 9) and most ITPNs/IOPNs showed consistent colabeling for CK7/MUC6, which was less common among others (P = .004). Intestinal-type IPNs (n = 5) showed higher rates of CK20 expression than others (P < .001). Overall, the most commonly mutated genes included TP53 and APC, while copy number variants affected ELF3 and CDKN2A/B. All gastric-type IPNs contained an alteration affecting the Wnt signaling pathway; 7 of 9 (78%) showed aberrations in the MAPK pathway. Mutations in APC and KRAS were common in gastric-type IPNs as compared with others (P = .01 for both). SMAD4 was more frequently mutated in intestinal-type IPNs (P = .02). Pancreatobiliary-type IPNs (n = 14) exhibited frequent alterations in tumor suppressor genes including TP53, CDKN2A/B, and ARID2 (P = .04, P = .01 and P = .002, respectively). Of 6 IOPNs analyzed, 3 (50%) revealed ATP1B1-PRKACB fusion. ITPNs (n = 6) showed relatively few recurrent genetic aberrations. Follow-up information was available for 38 patients (median, 58.5 months). The ratio of disease-related deaths was higher for the cases with invasion (56% versus 10%).

CONCLUSIONS.—

Tumoral intraductal neoplasms of the bile ducts, similar to their counterparts in the pancreas, are morphologically and genetically heterogeneous.

A Rare PDGFRA Exon 15 Germline Mutation Identified in a Patient With Phenotypic Manifestations Concerning for GIST-Plus Syndrome: A Case Report and Review of Literature

Molecular alterations in PDGFRA are well-described as drivers of sporadic gastrointestinal stromal tumors (GISTs) and inflammatory fibroid polyps (IFPs). However, a small number of families with germline PDGFRA mutations in exons 12, 14, and 18 have been reported, forming the basis of an autosomal dominant inherited disorder with incomplete penetrance and variable expressivity, now referred to as PDGFRA-mutant syndrome or GIST-plus syndrome. Phenotypic manifestations of this rare syndrome include multiple gastrointestinal GISTS, IFPs, fibrous tumors, and other variable features. Herein, we report the case of a 58-year-old female who presented with a gastric GIST and numerous small intestinal IFPs, found to harbor a previously undescribed germline PDGFRA exon 15 p.G680R mutation. Somatic tumor testing was performed on the GIST, a duodenal IFP, and an ileal IFP utilizing a targeted next-generation sequencing panel, revealing additional and distinct secondary PDGFRA exon 12 somatic mutations in each of the 3 tumors. Our findings raise important considerations regarding mechanisms of tumor development in patients with underlying germline PDGFRA alterations and highlight the potential utility of expanding currently available germline and somatic testing panels to include exons outside the typical hotspot regions.

What Is the Value of Counting Mast Cells in Gastrointestinal Mucosal Biopsies?

Neoplastic and nonneoplastic mast cell disorders can cause diarrhea, nausea, and abdominal pain that result from heightened release of mast cell mediators. Systemic mastocytosis is characterized by neoplastic mast cell aggregates in the bone marrow and other sites, particularly the skin and gastrointestinal tract. In this situation, extramedullary mast cell aggregates display atypical morphology, with aberrant immunostaining for CD25 in addition to staining for other mast cell markers, such as mast cell tryptase and CD117. Morphologically normal mast cells have also been implicated in nonneoplastic conditions. For example, increased mast cell numbers have been reported in the mucosal biopsy samples from patients with irritable bowel syndrome and hereditary alpha-tryptasemia. Patients with mast cell activation syndrome presumably experience symptoms related to the aberrant elaboration of histamine and other mediators from normal-appearing mast cells present in normal numbers. Unfortunately, similarities in terminology among these biologically distinct clinical conditions have caused considerable diagnostic confusion among clinical colleagues, resulting in frequent requests for pathologists to quantify and characterize mast cells in normal gastrointestinal biopsy samples from patients with diarrheal symptoms. The purpose of this review is to summarize the available data related to mast cell assessment in the gastrointestinal tract and provide pathologists with practical information so that they can help their clinical colleagues manage patients with presumed mast cell disorders.

GLI1 -Rearranged Enteric Tumor : Expanding the Spectrum of Gastrointestinal Neoplasms With GLI1 Gene Fusions

GLI1 encodes a transcription factor that targets cell cycle regulators affecting stem cell proliferation. GLI1 gene fusions were initially described in pericytomas with a t[7;12] translocation and more recently in gastric plexiform fibromyxomas and gastroblastomas. This study describes the clinicopathologic, immunohistochemical, and molecular features of three intestinal-based neoplasms harboring GLI1 gene fusions. We studied three unique mesenchymal small bowel tumors. Paraffin embedded tumor tissues from these cases and 62 additional tumor samples that included a plexiform fibromyxoma were sequenced using a targeted RNAseq method to detect fusion events. The study patients included two women and one man who were 52, 80, and 22 years of age at the time of diagnosis. The tumors involved the submucosa and muscularis propria of the duodenum, jejunum, and ileum. All 3 tumors contained a proliferation of monotonous oval or spindle cells with scattered, somewhat dilated vessels. Two cases showed epithelioid structures such as glands, tubules, or nests. Immunohistochemical analysis revealed cytokeratin expression in the epithelioid components of both tumors displaying these features, and variable numbers of mesenchymal cells. Diffuse CD56 positivity was seen in the mesenchymal component of 2 tumors and desmin and smooth muscle actin staining in the other tumor. Immunostains for S-100 protein, DOG-1, and CD117 were negative in all cases. GLI1 fusions with different partner genes were detected in all tumors, and in the plexiform fibromyxoma, used as a control. Validation by fluorescence in situ hybridization was performed. None of the tumors have recurred or metastasize after surgery. We describe novel GLI1 fusions in 3 mesenchymal neoplasms of the small intestine, including 2 with biphenotypic features. Thus far, all cases have pursued indolent clinical courses. We propose the term " GLI1 -rearranged enteric tumor" to encompass this group of unique neoplasms of the small intestine that harbor GLI1 gene fusions and expand the spectrum of gastrointestinal neoplasms with these alterations.

Abstract PR008: An epigenetic memory of inflammation controls context-dependent lineage plasticity and KRAS-driven tumorigenesis in the pancreas

Tissue homeostasis depends on responses to environmental insults to restore cellular phenotype, microenvironment composition, and tissue architecture. Inflammation is essential to the disruption of homeostasis, and, in the pancreas, can destabilize the identity of terminally differentiated acinar cells. Herein we employ lineage-traced mouse models to delineate the chromatin dynamics that accompany the cycle of metaplasia and regeneration following pancreatitis, and unveil the presence of an epigenetic memory of inflammation in the pancreatic acinar cell compartment. We observe that despite histologic resolution of pancreatitis, acinar cells fail to return to their molecular baseline after several months, representing an incomplete cell fate decision. In vivo, this epigenetic memory controls lineage plasticity, with diminished metaplasia in response to a second inflammatory insult but increased tumorigenesis with an oncogenic Kras mutation. We demonstrate that both persistent chromatin and transcriptional changes constituting memory are recalled with oncogenic stress. Together, our findings define a capacity for an environmental insult to control future cell-fate decisions in a context-dependent manner. The ability of epigenetic memory to potentiate tumor initiation both broadens the relationship between inflammation and cancer and raises the possibility that inducing epigenetic ‘amnesia’ of an inflammatory insult could be leveraged as a novel cancer prevention strategy.

Citation Format: David J. Falvo, Adrien Grimont, Paul Zumbo, Julie L. Yang, Alexa Osterhoudt, Grace Pan, Andre F. Rendeiro, John Erby Wilkinson, Friederike Dundar, Olivier Elemento, Rhonda K. Yantiss, Doron Betel, Richard Koche, Rohit Chandwani. An epigenetic memory of inflammation controls context-dependent lineage plasticity and KRAS-driven tumorigenesis in the pancreas. [abstract]. In: Proceedings of the AACR Special Conference: Cancer Epigenomics; 2022 Oct 6-8; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_2):Abstract nr PR008.

Abstract B055: Rac1 is essential for the maintenance of established KrasG12D-driven pancreatic ductal adenocarcinoma through senescence escape

The most prominent KRAS variants (G12D, G12V, G12R) that together represent around 80% of patients with pancreatic ductal adenocarcinoma (PDAC) are so far undruggable. While the role of several Kras mediators have been characterized in the initiation of PDAC, very little is known about the hierarchy of Kras effectors in the maintenance of the tumor. In recent years, strategies targeting the effectors downstream of mutant KRAS have offered scope for combined inhibition of EGFR and CRAF or MEK/RAF. However, these studies, unfortunately, have been limited by either narrow interrogation of downstream effectors in mouse models, or by the use of two-dimensional cell culture systems that may not recapitulate dependencies of the tumor in situ, respectively. To systematically interrogate the potential molecular dependencies in pancreatic tumor maintenance across several combinations of driver mutations, we have deployed in vitro and in vivo approaches in which we have selectively targeted key mediators of known KRAS-dependent pathways. These include Craf, Braf, PI3K, RalA, RalB, and Rac1, for which we have used inducible GFP-coupled shRNAs in 3D mouse and human tumor organoids harboring KrasG12D and p53R172H mutation. Using competition, cell cycle, and volumetric assays, we have uncovered that Rac1, Kras, and Craf are essential to the growth of PDAC organoids, whereas Braf, PI3K, RalA and RalB are dispensable. Interestingly, Rac1 depletion led to the strongest phenotype among the Kras mediators with a reduction of macropinocytosis, cell migration and colony formation in vitro. In an orthotopic pancreatic injection model, we observed that Rac1 inhibition in vivo led to diminished primary tumor growth, improved survival, and a reduction of metastatic incidence and outgrowth. In parallel, we performed RNA-sequencing on Kras-, Craf-, Rac1-, RalA- and Renilla-depleted organoids and found that Rac1 depletion rewires tumor cells to acquire a more PanIN-like phenotype, highlighting the importance of these proteins for the maintenance of PDAC cells. We also identify in Rac1- depleted cells evidence of deregulation of reactive oxygen species (ROS) and induction of a senescence-associated secretory phenotype (SASP) compared to control organoids. With a cytokine and chemokine array, we confirmed the increase of SASP chemokines (Csf3, Cxcl1, Cxcl2 and Cxcl5) and also detected bona fide senescence via SA-βgal staining. Finally, using several Rac1 inhibitors, we recapitulate the importance of Rac1 in PDAC growth. These data suggest that among the pleiotropic signaling downstream of mutant Kras, Rac1 is a critical node in PDAC maintenance that promotes tumor cell proliferation and senescence escape. Our findings point towards future efforts to couple Rac1 inhibition to define therapeutic synergies with immunotherapy and/or radiation. All together, we anticipate these findings can inform the subsequent development of novel therapies to address these vulnerabilities.

Citation Format: Adrien Grimont, David J. Falvo, Paul Zumbo, Grace Pan, John Nguyen, Rhonda K. Yantiss, Doron Betel, Laura Martin, Steven D. Leach, Rohit Chandwani. Rac1 is essential for the maintenance of established KrasG12D-driven pancreatic ductal adenocarcinoma through senescence escape [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr B055.

Abstract PR009: An epigenetic memory of inflammation controls context-dependent lineage plasticity in the pancreas

Inflammation is essential to the disruption of tissue homeostasis, and, in the pancreas, can destabilize the identity of terminally differentiated acinar cells. A longstanding question has been whether a history of past injuries instructs subsequent homeostatic responses to future stimuli – despite being distantly separated in time. Thus, we employ here Mist1-CreERT2; LSL-tdTomato lineage-tracing mice to investigate the long-term effects of a transient inflammatory episode on pancreatic tissue homeostasis. We delineate the chromatin dynamics that accompany the cycle of metaplasia and regeneration following pancreatitis, and reveal that the pancreatic acinar cell compartment durably retains specific inflammation-induced epigenetic changes even 18-weeks after exposure to the original inflammatory stimulus. We observe that despite histologic resolution of pancreatitis, acinar cells fail to return to their molecular baseline after several months, representing an incomplete cell fate decision. Motif analysis demonstrates the enrichment of AP-1/Fra1 motifs at these persistently accessible memory regions—a transcriptional effector activated downstream of the Ras/MAPK pathway. This epigenetic memory controls lineage plasticity, with diminished metaplasia in response to a second inflammatory insult but increased tumorigenesis with an oncogenic Kras mutation. We demonstrate that pancreatic acinar cells exhibit rapid malignant transformation upon re-challenge with oncogenic stress via inflammatory memory recall, with robust reactivation of genes associated with differentially accessible memory regions. Together, our findings define the dynamics and recall of an epigenetic memory of inflammation that impacts cell fate decisions in a context-dependent manner.

Citation Format: David J. Falvo, Adrien Grimont, Paul Zumbo, Julie L. Yang, Alexa Osterhoudt, Grace Pan, Andre F. Rendeiro, John E. Wilkinson, Friederike Dündar, Olivier Elemento, Rhonda K. Yantiss, Doron Betel, Richard Koch, Rohit Chandwani. An epigenetic memory of inflammation controls context-dependent lineage plasticity in the pancreas [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr PR009.

The pathogenesis of coronavirus-19 disease

Severe acute respiratory syndrome-associated coronavirus-2 (SARS-CoV-2) is the causal agent of coronavirus disease-2019 (COVID-19), a systemic illness characterized by variably severe pulmonary symptoms, cardiac conduction abnormalities, diarrhea, and gastrointestinal bleeding, as well as neurologic deficits, renal insufficiency, myalgias, endocrine abnormalities, and other perturbations that reflect widespread microvascular injury and a pro-inflammatory state. The mechanisms underlying the various manifestations of viral infection are incompletely understood but most data suggest that severe COVID-19 results from virus-driven perturbations in the immune system and resultant tissue injury. Aberrant interferon-related responses lead to alterations in cytokine elaboration that deplete resident immune cells while simultaneously recruiting hyperactive macrophages and functionally altered neutrophils, thereby tipping the balance from adaptive immunity to innate immunity. Disproportionate activation of these macrophages and neutrophils further depletes normal activity of B-cells, T-cells, and natural killer (NK) cells. In addition, this pro-inflammatory state stimulates uncontrolled complement activation and development of neutrophil extracellular traps (NETS), both of which promote the coagulation cascade and induce a state of “thrombo-inflammation”. These perturbations have similar manifestations in multiple organ systems, which frequently show pathologic findings related to microvascular injury and thrombosis of large and small vessels. However, the pulmonary findings in patients with severe COVID-19 are generally more pronounced than those of other organs. Not only do they feature inflammatory thromboses and endothelial injury, but much of the parenchymal damage stems from failed maturation of alveolar pneumocytes, interactions between type 2 pneumocytes and non-resident macrophages, and a greater degree of NET formation. The purpose of this review is to discuss the pathogenesis underlying organ damage that can occur in patients with SARS-CoV-2 infection. Understanding these mechanisms of injury is important to development of future therapies for patients with COVID-19, many of which will likely target specific components of the immune system, particularly NET induction, pro-inflammatory cytokines, and subpopulations of immune cells.

Interval Appendectomy Specimens

CONTEXT.—

Patients with perforated appendicitis are often managed with antibiotic therapy followed by a delayed appendectomy. Histologic features of such specimens have been incompletely described, especially in the recent literature.

OBJECTIVE.—

To describe the histomorphology of interval appendicitis with a focus on features that could mimic important conditions, such as infections, Crohn disease, and mucinous neoplasms.

DESIGN.—

Histologic evaluation of 100 interval appendectomy specimens with clinical and radiologic correlation.

RESULTS.—

A total of 54 of the 100 patients (54%) had radiologic evidence of appendiceal perforation, and 97% were treated with intravenous and/or oral antibiotic therapy prior to appendectomy. Percutaneous drains were placed in 34 cases (34%). Common histologic findings included mural eosinophilic infiltration (54%), periappendiceal fibrosis (54%), and xanthogranulomatous inflammation (31%). Periappendiceal fibrosis was frequent among patients with radiologic evidence of perforation. Nine cases (9%) featured pulse granulomata associated with fecal material. Epithelioid granulomata were detected in 6% of cases and were confined to mucosal lymphoid follicles in all cases. Only 4 of these were accompanied by mural lymphoid aggregates that raised the possibility of Crohn disease. Changes mimicking mucinous neoplasms were more common: 14% of cases (14 of 100) displayed goblet cell hyperplasia, 15% (15 of 100) contained diverticula, and 16% (16 of 100) showed mural or periappendiceal mucin pools.

CONCLUSIONS.—

Although interval appendectomy specimens occasionally contain inflammatory infiltrates that mimic infections and/or Crohn disease, changes that can be confused with mucinous neoplasms are more frequently encountered.

Gastrointestinal, Hepatic and Pancreatobiliary Involvement by Plasma Cell Neoplasms: Clinicopathologic Correlations in a Retrospective Cohort of 116 Cases

AIMS

Plasma cell neoplasms (PCNs) may involve the gastrointestinal (GI) tract in two forms: plasmacytoma (PC), an isolated lesion which lacks marrow involvement, and extramedullary myeloma (EMM). However, previous literature on PCNs involving the GI tract, liver and pancreas is limited. We evaluated the clinicopathologic features of the largest series of GI PCNs to date.

METHODS AND RESULTS

Six institutional archives were searched for GI, liver and pancreas cases involved by PCNs. Medical records were reviewed for clinical and imaging features. Histopathologic features evaluated included involved organ, tumor grade and marrow involvement. Overall, 116 cases from 102 patients were identified. Tumors most presented as incidental findings (29%). The liver was most involved (47%), and masses/polyps (29%) or ulcers (21%) were most common findings. Most cases had high-grade morphology (55%). The majority (74%) of GI PCNs were classified as EMM due to the presence of marrow involvement at some point during the disease course, occurring within a year of marrow diagnosis in 46% of patients. PC was classified in 26% of patients due to the lack of marrow involvement. Most (70%) patients died from disease within 10 years (median 14.1) of diagnosis and more than half (58%) died within 6 months.

CONCLUSION

PC and EMM involving the GI tract, liver and pancreas have a wide range of clinicopathologic presentations. Tumors may occur virtually anywhere in the GI tract or abdomen and may precede the diagnosis of marrow involvement. Both GI PC and EMM are associated with a poor prognosis.

Histological features of Clostridioides difficile colitis in patients with inflammatory bowel disease

AIMS

Patients with inflammatory bowel disease (IBD) are at increased risk for Clostridioides difficile infection, although clinically important infections can be difficult to recognise. C. difficile infection does not produce pseudomembranes when it occurs in IBD patients. These individuals may also be colonised by the organism, in which case diarrhoeal symptoms are not necessarily attributed to C. difficile. We performed this study to determine whether any features distinguished C. difficile-associated colitis from an IBD flare.

METHODS AND RESULTS

We reviewed the clinical, endoscopic and biopsy findings from 50 patients with established IBD and worsening diarrhoea, including 22 with concurrent positive C. difficile stool toxin polymerase chain reaction (PCR) assays and 28 with negative C. difficile assay results. We found that C. difficile-infected patients had symptoms and endoscopic findings that were indistinguishable from active IBD. Although most biopsy samples from patients with C. difficile infection showed chronic active colitis indistinguishable from IBD, some displayed neutrophilic infiltrates unaccompanied by plasma cell-rich inflammation involving superficial (41%) and crypt (18%) epithelium as well as neutrophilic infiltrates within lamina propria distant from foci of cryptitis (32%). All three of these features were significantly more common among infected than uninfected patients (4, 0 and 4%; P = 0.002, P = 0.03 and P = 0.02, respectively).

CONCLUSIONS

Although colonic biopsies from IBD patients with C. difficile infection usually lack features that aid distinction from colitic flares, some cases show an acute colitis pattern not seen in IBD alone. When identified in biopsies from symptomatic IBD patients, these changes should alert pathologists to the possibility of this clinically important infection.

Mucosal fungi promote gut barrier function and social behavior via Type 17 immunity

Fungal communities (the mycobiota) are an integral part of the gut microbiota, and the disruption of their integrity contributes to local and gut-distal pathologies. Yet, the mechanisms by which intestinal fungi promote homeostasis remain unclear. We characterized the mycobiota biogeography along the gastrointestinal tract and identified a subset of fungi associated with the intestinal mucosa of mice and humans. Mucosa-associated fungi (MAF) reinforced intestinal epithelial function and protected mice against intestinal injury and bacterial infection. Notably, intestinal colonization with a defined consortium of MAF promoted social behavior in mice. The gut-local effects on barrier function were dependent on IL-22 production by CD4⁺ T helper cells, whereas the effects on social behavior were mediated through IL-17R-dependent signaling in neurons. Thus, the spatial organization of the gut mycobiota is associated with host-protective immunity and epithelial barrier function and might be a driver of the neuroimmune modulation of mouse behavior through complementary Type 17 immune mechanisms.

Crohn Disease Infrequently Affects the Appendix and Rarely Causes Granulomatous Appendicitis

Data from previous studies suggest Crohn disease of the appendix accounts for ∼25% of granulomatous appendicitis cases. However, we have found that granulomatous inflammation in appendectomy specimens rarely heralds Crohn disease. We suspect that appendiceal involvement by Crohn disease is uncommon, even when patients have severe ileocolonic inflammation. We performed this study to determine the prevalence and nature of appendiceal inflammation among patients with Crohn disease. We reviewed 100 ileocolic specimens with strictures and fistulizing Crohn disease for the nature and distribution of inflammatory changes in the appendix and compared them with 100 appendices on colectomy specimens from age-matched and sex-matched patients with ulcerative colitis. We also evaluated 27 additional cases of granulomatous appendicitis in appendectomy specimens to determine the frequency with which this finding represented Crohn disease. The appendix was usually normal (26%) or showed fibrous obliteration (50%) in ileocolic resection specimens from patients with Crohn disease. Mucosal inflammation was much less common in appendices from patients with Crohn disease than ulcerative colitis (6% vs. 28%, P<0.0001); only 4 cases contained epithelioid granulomata, 3 showed mural fibrosis and lymphoid aggregates, and 10 displayed only periappendiceal inflammation. None of the patients with granulomatous appendicitis in appendectomy specimens had, or developed, evidence of Crohn disease. We conclude that Crohn disease infrequently affects the appendix. Interval appendectomy and infection are more important considerations when appendectomy specimens feature granulomatous inflammation and/or mural lymphoid aggregates, especially if there is no history of idiopathic inflammatory bowel disease.

Controversies in appendiceal pathology: Mucinous and goblet cell neoplasms

Appendiceal goblet cell adenocarcinomas and mucinous neoplasms are uncommon compared with other epithelial tumours of the gastrointestinal tract. Both tumour types have been subjected to terminology that belies their biological risk and leads to confusion. Goblet cell adenocarcinomas display patchy staining for endocrine markers and, thus, were previously classified as goblet cell carcinoids. Unlike well-differentiated endocrine neoplasms, however, they often contain high-grade glandular elements and pursue an aggressive course akin to that of conventional adenocarcinoma. Although several authors have recently proposed grading schemes to predict behaviour among goblet cell neoplasms, most that contain high-grade components have already spread beyond the appendix at the time of diagnosis, whereas those confined to the appendix almost always have low-grade features; the added value of grading these tumours is limited. Contradictions also surround the nomenclature of mucinous neoplasms. The World Health Organization and others promote non-malignant terminology to describe metastatic mucinous neoplasms of the peritoneum and eliminate a benign category entirely, even though virtually all neoplasms confined to the appendix pose no recurrence risk following appendectomy. 'Low-grade appendiceal mucinous neoplasm' now encompasses a spectrum of benign tumours and malignant neoplasms in the appendix and peritoneum. Although using an umbrella term in this fashion simplifies the roles of pathologists, it provides essentially no actionable information beyond that which is already clinically apparent. Broad strokes nomenclature also ensures that many patients with no risk of recurrence will receive unnecessary surveillance while others will undergo inappropriate surgical procedures due to lapses in communication. Moreover, a surprising number of non-neoplastic mucinous lesions are misclassified as low-grade appendiceal mucinous neoplasms, which can result in unwarranted patient concern or even mismanagement. The purpose of this review is to critically evaluate the literature and describe an approach to appendiceal neoplasms that more clearly denotes their biologic risk.

High interobserver variability and frequent overdiagnosis of dysplasia in fundic gland polyps can be improved by detecting atypia on the surface epithelium and an abrupt transition to non-neoplastic cells

AIMS

Fundic gland polyps (FGPs) arise sporadically and in combination with familial adenomatous polyposis (FAP). Criteria for distinguishing low-grade dysplasia (LGD) from regenerative atypia in FGPs are not well established. The aims of study were to determine: (i) interobserver variability in diagnosing LGD in FGPs; (ii) bias in diagnosing LGD in FAP patients; and (iii) stringent criteria for LGD in FGPs.

METHODS AND RESULTS

Five senior pathologists who were blinded to the clinical history reviewed 72 FAP-associated FGPs and 34 sporadic FGPs. Cases were classified as negative (score = 0) or positive (score = 1) for LGD. Each case was assigned a 'combined dysplasia score' (CDS) ranging from 0 to 5 to reflect all five opinions. Fleiss' kappa showed only moderate interobserver agreement (κ = 0.46). Forty-one FGPs were classified as negative for dysplasia by consensus (CDS = 0-1), including 10 (24%) originally diagnosed as LGD. In contrast, all 37 cases classified as LGD by consensus (CDS = 4-5) were originally diagnosed as LGD, indicating that overdiagnosis of dysplasia is more common than underdiagnosis (P = 0.0012). Cytological atypia in the surface epithelium and an abrupt transition between atypical and normal-appearing epithelium were the most sensitive (97% and 100%, respectively) and specific (100% and 98%, respectively) features of dysplasia (P < 0.0001 for both comparisons). Very good agreement was achieved when a diagnosis of dysplasia was based on the presence of both features (κ = 0.85).

CONCLUSIONS

There is high interobserver variability and a tendency to overdiagnose LGD in FGPs. Strict criteria requiring both surface atypia and abrupt transition for LGD in FGPs result in low interobserver variability.

GLUT5 is a determinant of dietary fructose-mediated exacerbation of experimental colitis

The Western diet has been suggested to contribute to the rising incidence of inflammatory bowel diseases. This has led to the hypothesis that fructose, a component of the Western diet, could play a role in the pathogenesis of inflammatory bowel diseases. A high-fructose diet is known to exacerbate experimental colitis. This study tested whether the expression of GLUT5, the fructose transporter, is a determinant of the severity of experimental colitis during elevated fructose consumption and whether ileal inflammation is associated with altered GLUT5 expression in Crohn's disease. Studies in genetically engineered mice showed that in comparison to Glut5^+/+ mice, feeding a 15 kcal% fructose diet to Glut5^-/- mice led to worse dextran sodium sulfate (DSS)-induced colitis. This effect was associated with elevated levels of colonic fructose and a shift in the fecal microbiota in Glut5^-/- mice. Importantly, treatment with broad-spectrum antibiotics protected against the worsening of colitis mediated by dietary fructose in Glut5^-/- mice. Gene expression analysis revealed that GLUT5 levels are reduced in the intestines of patients with ileal Crohn's disease. Moreover, levels of GLUT5 negatively correlated with expression of proinflammatory mediators in these samples. Collectively, these results demonstrate that dietary constituent (fructose)-host gene (GLUT5) interactions can shape the colonic microbiota, thereby impacting the severity of colitis.NEW & NOTEWORTHY This study provides the first evidence that reduced levels of GLUT5, the fructose transporter, worsen experimental colitis upon fructose feeding, an effect mediated by changes in the gut microbiota. Moreover, GLUT5 expression is reduced in Crohn's ileitis. Overall, these findings demonstrate the importance of interactions between dietary fructose and host GLUT5 as determinants of both the composition of colonic microbiota and severity of experimental colitis.

Abstract 3182: Tumor immune microenvironment based molecular functional clustering reveals a prognostic signature that predicts overall survival in patients with gastric cancer

Gastric Cancer (GC) is the second leading cause of cancer-related mortality (9.7% of the total) and most patients with advanced disease will die within one year of diagnosis. GC is histologically classified into intestinal, diffuse and the mixed types, and into four molecular subtypes based on genetic profiling (i.e. microsatellite instable (MSI), EBV positive, chromosomal instable, and genomically stable). Although the molecular annotation is meaningful, the tumor immune microenvironment (TIME) has largely not been evaluated. Using an integrated collection of 11 public cohorts (n=2,270), we identified 5 unique GC TIME phenotypes by unsupervised clustering of gene expression signatures of RNA that describe the composition and biology of TIME and properties of malignant cells: two stromal-enriched subtypes - 1) Mesenchymal-wnt activated, high stroma activation and WNT signaling and 2) Fibrotic, only high stroma activation; two immune enriched subtypes 3) Inflamed non-fibrotic, high immune infiltration and low stromal compartment and 4) B-cell inflamed, high B cell activation; and 5) Immune Depleted, lowest immune and the highest malignant cell properties. The clusters were robust, being identified across all 11 datasets and across all stages of disease. Intestinal, diffuse, and mixed histologies were identified in each cluster. These clusters will be orthogonally validated using immunohistochemistry.

The current molecular subtypes were represented in each of our TIME clusters, with some enrichment. Specifically, we found enrichment of MSI molecular subtype, characterized by hypermutation and microsatellite instability, in “Inflamed, non-fibrotic” cluster whereas the MSS/EMT subtype, associated with poor overall survival, was enriched in “Mesenchymal, wnt activated” cluster. We also saw specific enrichment of EBV positive tumors, known to have good prognosis, in both immune-enriched clusters. These results show a high concordance with the current TCGA/ACRG molecular subtypes of GC.

These TIME clusters are prognostic in GC. The “Inflamed, non-fibrotic” cluster demonstrated a better overall and relapse free survival whereas stromal enriched clusters exhibited the worst (p&lt;0.001, HR=2.27). Interestingly, the most aggressive “Mesenchymal, wnt activated” subtype was also enriched of metastatic samples. These results were confirmed using an independent validation cohort (n=231) from four other datasets. Additionally, comparison of matching on-treatment vs baseline biopsies from 7 patients treated with cabazitaxel further suggested that TIME changed upon treatment and, in some cases, was indicative of poor response to taxanes.

We have defined and characterized the TIME for GC. The GC microenvironment is both prognostic for patient outcome and predictive of response to cytotoxic therapy.

Citation Format: Prashant V. Thakkar, Olga Kudryashova, Daria Melikhova, Naira Samarina, Sandrine Degryse, Alexander Bagaev, Felix Frenkel, Svetlana Podsvirova, Dmitry Tychinin, Sandipto Sarkar, Rhonda K. Yantiss, Nathan Fowler, Manish A. Shah. Tumor immune microenvironment based molecular functional clustering reveals a prognostic signature that predicts overall survival in patients with gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 3182.

Epithelial-Stromal Polyps of the Colon Are Not Perineuriomas

OBJECTIVES

Some colorectal polyps contain serrated or tubular crypts surrounded by whorls of spindle cells that expand the mucosa. These epithelial-stromal polyps have been termed benign fibroblastic polyps or, more commonly, perineuriomas. We hypothesized that these lesions are pathogenetically heterogeneous polyps that share in common exuberant fibroblastic proliferations derived from the pericryptal sheath.

METHODS

Forty-six epithelial-stromal polyps containing serrated crypts (n = 21) and nonserrated crypts (n = 25) were evaluated with epithelial membrane antigen and BRAF V600E immunohistochemical stains, and a subset was subjected to next-generation sequencing for BRAF mutations. Polyp morphology and immunohistochemical results were correlated with clinical information.

RESULTS

Epithelial-stromal polyps containing serrated crypts were significantly associated with other sessile serrated polyps (43%, P = .01) and hyperplastic polyps (29%, P = .006). They also showed BRAF V600E abnormalities (95%) and strong, patchy epithelial membrane antigen staining of spindle cells (95%). In contrast, polyps with nonserrated crypts lacked BRAF alterations and infrequently showed robust EMA staining of stromal cells (16%, P < .01).

CONCLUSIONS

Benign epithelial-stromal polyps with serrated epithelium are biologically similar to sessile serrated polyps and should be classified as such to ensure appropriate clinical surveillance. The nature of polyps without serrated crypts is less clear, but evidence that they are perineuriomas is circumstantial at best.

Dietary interventions to prevent high-fructose diet-associated worsening of colitis and colitis-associated tumorigenesis in mice

Diet is believed to be an important factor in the pathogenesis of inflammatory bowel disease. High consumption of dietary fructose has been shown to exacerbate experimental colitis, an effect mediated through the gut microbiota. This study evaluated whether dietary alterations could attenuate the detrimental effects of a high-fructose diet (HFrD) in experimental colitis. First, we determined whether the procolitic effects of a HFrD could be reversed by switching mice from a HFrD to a control diet. This diet change completely prevented HFrD-induced worsening of acute colitis, in association with a rapid normalization of the microbiota. Second, we tested the effects of dietary fiber, which demonstrated that psyllium was the most effective type of fiber for protecting against HFrD-induced worsening of acute colitis, compared with pectin, inulin, or cellulose. In fact, supplemental psyllium nearly completely prevented the detrimental effects of the HFrD, an effect associated with a shift in the gut microbiota. We next determined whether the protective effects of these interventions could be extended to chronic colitis and colitis-associated tumorigenesis. Using the azoxymethane/dextran sodium sulfate model, we first demonstrated that HFrD feeding exacerbated chronic colitis and increased colitis-associated tumorigenesis. Using the same dietary changes tested in the acute colitis setting, we also showed that mice were protected from HFrD-mediated enhanced chronic colitis and tumorigenesis, upon either diet switching or psyllium supplementation. Taken together, these findings suggest that high consumption of fructose may enhance colon tumorigenesis associated with long-standing colitis, an effect that could be reduced by dietary alterations.

The diagnosis of clinically significant oesophageal Candida infections: a reappraisal of clinicopathological findings

AIMS

Distinguishing true oesophageal Candida infections from oral contaminants is a common diagnostic issue. Historically, histological features believed to indicate true infection included epithelial invasion by pseudohyphae and intraepithelial neutrophils. Whether or not these features correlate with endoscopic lesions, symptoms and response to therapy has never been tested in a large cohort. The aim of this study was to determine whether specific histological features correlate with clinical and endoscopic findings when Candida is found in oesophageal biopsies.

METHODS AND RESULTS

We reviewed 271 biopsies in which Candida was detected. Cases were evaluated for the presence of desquamated epithelial cells, location/type of fungal forms, neutrophils, and ulceration. Medical records were reviewed for clinical history, endoscopic lesions, and response to antifungal therapy. Statistical analysis was used to determine whether any histological features significantly correlated with clinical variables. There were 120 males and 151 females with a mean age of 42 years. Fifty-nine per cent had symptoms referable to the oesophagus, particularly dysphagia (36%). Most (73%) patients had abnormal endoscopic findings, with plaques, ulcers, or macroscopic evidence of oesophagitis. Seventy-one per cent of patients with documented antifungal therapy showed symptomatic improvement. Overall, there was no statistically significant correlation between any histological feature and presenting symptoms, endoscopic findings, or response to therapy. Importantly, the lack of pseudohyphae, demonstrable invasion of intact epithelium or neutrophilic infiltrates did not exclude clinically significant infection.

CONCLUSIONS

We conclude that detection of Candida in oesophageal biopsies is always potentially clinically significant. Treatment decisions should be made on the basis of an integration of clinical, endoscopic and histological findings.

Exogenous and Endogenous Sources of Serine Contribute to Colon Cancer Metabolism, Growth, and Resistance to 5-Fluorouracil

Serine is a nonessential amino acid generated by the sequential actions of phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase (PSAT1), and phosphoserine phosphatase (PSPH). Increased serine biosynthesis occurs in several cancers and supports tumor growth. In addition, cancer cells can harness exogenous serine to enhance their metabolism and proliferation. Here we tested the relative contributions of exogenous and endogenous sources of serine on the biology of colorectal cancer. In murine tumors, Apc status was identified as a determinant of the expression of genes controlling serine synthesis. In patient samples, PSAT1 was overexpressed in both colorectal adenomas and adenocarcinomas. Combining genetic deletion of PSAT1 with exogenous serine deprivation maximally suppressed the proliferation of colorectal cancer cells and induced profound metabolic defects including diminished nucleotide production. Inhibition of serine synthesis enhanced the transcriptional changes following exogenous serine removal as well as alterations associated with DNA damage. Both loss of PSAT1 and removal of serine from the diet were necessary to suppress colorectal cancer xenograft growth and enhance the antitumor activity of 5-fluorouracil (5-FU). Restricting endogenous and exogenous serine in vitro augmented 5-FU-induced cell death, DNA damage, and metabolic perturbations, likely accounting for the observed antitumor effect. Collectively, our results suggest that both endogenous and exogenous sources of serine contribute to colorectal cancer growth and resistance to 5-FU. SIGNIFICANCE: These findings provide insights into the metabolic requirements of colorectal cancer and reveal a novel approach for its treatment. GRAPHICAL ABSTRACT: http://cancerres.aacrjournals.org/content/canres/81/9/2275/F1.large.jpg.

Tumor regression grading after neoadjuvant treatment of esophageal and gastroesophageal junction adenocarcinoma: results of an international Delphi consensus survey

Complete histopathologic tumor regression after neoadjuvant treatment is a well-known prognostic factor for survival among patients with adenocarcinomas of the esophagus and gastroesophageal junction. The aim of this international Delphi survey was to reach a consensus regarding the most useful tumor regression grading (TRG) system that could represent an international standard for histopathologic TRG grading of gastroesophageal carcinomas. Fifteen pathologists with special interest in esophageal and gastric pathology participated in the online survey. The initial questionnaire contained of 43 statements that addressed the following topics: (1) specimen processing, (2) gross examination, (3) cross sectioning, (4) staining, (5) Barrett's esophagus, (6) TRG systems, and (7) TRG in lymph node (LN). Participants rated the items using a 5-point Likert style scale and were encouraged to write comments for each statement. The expert panel recommended a 4-tiered TRG system for assessing the primary tumor: grade 1: No residual tumor (complete histopathologic tumor regression), grade 2: less than 10% residual tumor (near-complete regression), grade 3: 10%-50% residual tumor (partial regression), grade 4: greater than 50% residual tumor (minimal/no regression), combined with a 3-tiered system for grading therapeutic response in metastatic LNs: grade a: no residual tumor (complete histopathologic TRG), grade b: partial regression (tumor cells and regression), grade c: no regression (no sign of tumor response). This TRG grading system can be recommended as an international standard for histopathologic TRG grading in esophageal and gastroesophageal junction adenocarcinoma.

Autopsy Findings in 32 Patients with COVID-19: A Single-Institution Experience

Background

A novel coronavirus, SARS-CoV-2, was identified in Wuhan, China in late 2019. This virus rapidly spread around the world causing disease ranging from minimal symptoms to severe pneumonia, which was termed coronavirus disease (i.e., COVID). Postmortem examination is a valuable tool for studying the pathobiology of this new infection.

Methods

We report the clinicopathologic findings from 32 autopsy studies conducted on patients who died of COVID-19 including routine gross and microscopic examination with applicable special and immunohistochemical staining techniques.

Results

SARS-CoV-2 infection was confirmed by nasopharyngeal RT-PCR in 31 cases (97%) and by immunohistochemical staining for SARS-CoV-2 spike-protein in the lung in the remaining 1 case (3%). The ethnically diverse cohort consisted of 22 males and 10 females with a mean age of 68 years (range: 30–100). Patients most commonly presented with cough (17 [55%]), shortness of breath (26 [81%]), and a low-grade fever (17 [55%]). Thirty-one (97%) of the patients had at least 1 comorbidity (mean = 4). Twenty-eight patients (88%) had widespread thromboembolic disease, as well as diffuse alveolar damage (30 [94%]), diabetic nephropathy (17 [57%]) and acute tubular injury. Patterns of liver injury were heterogeneous, featuring 10 (36%) with frequent large basophilic structures in sinusoidal endothelium, and increased immunoblast-like cells in lymph nodes.

Conclusion

This series of autopsies from patients with COVID-19 confirms the observation that the majority of severely affected patients have significant pulmonary pathology. However, many patients also have widespread microscopic thromboses, as well as characteristic findings in the liver and lymph nodes.

Abstract 3745: Exogenous and endogenous sources of serine contribute to colon cancer metabolism and growth

Serine is a non-essential amino acid that is generated by the sequential actions of phosphoglycerate dehydrogenase (PHGDH), phosphoserine aminotransferase (PSAT1) and phosphoserine phosphatase (PSPH). Increased serine biosynthesis occurs in several cancers and supports tumor growth. In addition to serine synthesis, exogenous serine is taken up by cells and can also fuel tumor growth. Interestingly, colon cancer cells increase expression of serine biosynthesis enzymes in the absence of exogenous serine, suggesting a compensatory adaptive response to reduced availability of serine. This study explored the relative contributions of exogenous and synthesized serine to colon cancer cell growth, metabolism and response to anti-cancer therapy. We found that PSAT1 expression was markedly increased in human colonic adenomas and colorectal cancer (CRC) compared to normal adjacent tissue. Additionally, high levels of PSAT1 in CRC were associated with reduced patient survival. Deletion of PSAT1 only modestly reduced colon cancer cell proliferation in vitro. Removal of serine from the medium strongly suppressed cell proliferation whereas the combination of removing exogenous serine and deleting PSAT1 caused even greater inhibition of cell proliferation. Metabolite profiling revealed altered nucleotide levels upon exogenous serine depletion, an effect that was enhanced when PSAT1 was deleted. Global gene expression profiling showed approximately 3,000 differentially expressed genes when only exogenous serine was removed, with an additional ~800 changes in PSAT1 knockout (KO) cells grown in serine deficient medium. A marked DNA damage response was induced selectively in PSAT1KO cells in serine deficient medium, which was prevented by the addition of formate. Xenografts derived from PSAT1 sufficient and PSAT1KO cells showed that neither PSAT1 deletion alone nor removal of dietary serine alone affected tumor growth, but the combination resulted in profound growth suppression. Additionally, treatment with 5-fluorouracil (5-FU) in the xenograft model induced a strong regression of established tumors derived from mice carrying PSAT1KO cells fed a serine deficient diet. Complementary in vitro studies showed enhanced sensitivity of PSAT1KO cells grown in serine deficient medium to 5-FU induced death, which was preceded by specific metabolite changes including markedly reduced levels of TMP and TTP. Taken together, our results suggest that both exogenous and endogenous sources of serine are important contributors to colon cancer cell proliferation and metabolism. Limiting exogenously available and synthesized serine may be an effective strategy to limit colon cancer growth and enhance the efficacy of treatment.

Citation Format: David C. Montrose, Miguel Foronda, Suchandrima Saha, Erin M. McNally, Xi Kathy Zhou, Jan Krumsiek, Akanksha Verma, Olivier Elemento, Rhonda K. Yantiss, Qiuying Chen, Steven S. Gross, Lorenzo Galluzzi, Lukas E. Dow, Andrew J. Dannenberg. Exogenous and endogenous sources of serine contribute to colon cancer metabolism and growth [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3745.

Abstract 3461: Psyllium protects against high fructose diet induced exacerbation of colitis and colitis associated colorectal carcinogenesis

Patients with longstanding Inflammatory Bowel Disease, including ulcerative colitis and Crohn's disease, are at an increased risk of developing colorectal cancer (CRC). Over the past three decades, there has been a significant increase in the consumption of fructose, a monosaccharide that has been linked to increased growth of experimental intestinal tumors. Additionally, recent evidence shows that feeding a diet high in fructose worsens acute experimental colitis. The aims of the current study were to 1) determine if a high fructose diet (HFrD) exacerbated chronic colitis in mice and led to enhanced colorectal tumorigenesis and 2) evaluate the potential chemopreventive properties of dietary fiber in this context. To carry this out, the azoxymethane (AOM)/DSS model of colitis-associated colorectal neoplasia was utilized in male C57BL/6J mice. In comparison to control AIN93G diet, an isocaloric diet supplemented with fructose led to worse chronic colitis including weight suppression, worse diarrhea, colon shortening and a higher histologic score. Tumor incidence, number and size were all increased (Ps&lt;0.001) in the HFrD compared to control diet group. Because eliminating fructose from the diet is impractical, it is important to identify other potential dietary constituents that may minimize its harmful effects. Dietary fiber has been suggested to be beneficial for reducing the severity of colitis. Therefore, we next determined whether the severity of HFrD-associated acute colitis was altered by dietary psyllium, pectin, inulin or cellulose fibers. In comparison to the other three fibers, psyllium protected against acute DSS- induced colitis. It also led to a significant shift in the fecal microbiota. Finally, we tested whether psyllium would attenuate the worsening of chronic colitis and colitis-associated colorectal neoplasia mediated by HFrD. Using the AOM/DSS model, we found that psyllium fiber protected against the exacerbation of chronic colitis mediated by HFrD with improved diarrhea, bleeding and histologic score. Consistent with its ability to suppress HFrD-mediated exacerbation of chronic colitis, psyllium markedly suppressed the increase in colorectal tumor incidence, number and size in mice that received the HFrD. Taken together, these results indicate that feeding a HFrD exacerbated chronic colitis leading to increased colitis-associated colorectal tumorigenesis. Supplemental psyllium fiber attenuated these procarcinogenic effects of a HFrD.

Citation Format: Srijani Basu, Ryohei Nishiguchi, David C. Montrose, Hannah Staab, Xi Kathy Zhou, Hanhan Wang, Melanie Johncilla, Rhonda K. Yantiss, Andrew Dannenberg. Psyllium protects against high fructose diet induced exacerbation of colitis and colitis associated colorectal carcinogenesis [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3461.

Histology of Colorectal Carcinoma: Proven and Purported Prognostic Factors

Although tumor stage has a profound influence on prognosis, several histologic features are also important. These parameters predict biological behavior and can be used by clinicians to determine whether patients are at high risk for disease progression and, thus, are candidates for adjuvant therapy, particularly when they have localized (ie, stage II) disease. This article summarizes the evidence supporting the prognostic values of various histologic parameters evaluated by pathologists who assign pathologic stage to colorectal cancers. Criteria to be discussed include histologic subtype, tumor grade, lymphatic and perineural invasion, tumor budding, and host immune responses.

Smooth muscle tumors of the gastrointestinal tract: an analysis of prognostic features in 407 cases

Smooth muscle tumors represent the second most common mural mesenchymal neoplasm in the gastrointestinal tract, but established criteria for prognostic assessment of these tumors are lacking. A large cohort of surgically resected intramural gastrointestinal smooth muscle tumors from 31 institutions was analyzed to identify potential prognostic features. Pathologic features were assessed by expert gastrointestinal and/or soft tissue pathologists at each center. Immunohistochemical confirmation was required. A total of 407 cases from the esophagus (n = 97, 24%), stomach (n = 180, 44%), small bowel (n = 74, 18%), and colorectum (n = 56, 14%) were identified. Patients ranged in age from 19 to 92 years (mean 55 years), with a slight female predominance (57%). Mean tumor size was 5.4 cm, with the largest tumor measuring 29 cm. Disease progression following surgery, defined as local recurrence, metastasis, or disease-related death, occurred in 56 patients (14%). Colorectal tumors were most likely to progress, followed by small bowel and gastric tumors. None of the esophageal tumors in this series progressed. Receiver operator characteristic analysis identified optimal cutoffs of 9.8 cm and 3 mitoses/5 mm² for discriminating between progressive and non-progressive tumors. Histologic features strongly associated with progression by univariate analysis included moderate-to-severe atypia, high cellularity, abnormal differentiation (defined as differentiation not closely resembling that of normal smooth muscle), tumor necrosis, mucosal ulceration, lamina propria involvement, and serosal involvement (P < 0.0001 for all features). Age, sex, and margin status were not significantly associated with progression (P = 0.23, 0.82, and 0.07, respectively). A risk assessment table was created based on tumor site, size, and mitotic count, and Kaplan-Meier plots of progression-free survival for each subgroup revealed progression-based tiers. Based on our findings, it appears that nonesophageal gastrointestinal smooth muscle tumors measuring >10 cm and/or showing ≥3 mitoses/5 mm² may behave aggressively, and therefore close clinical follow-up is recommended in these cases.

Next-generation sequencing of residual cytologic fixative preserved DNA from pancreatic lesions: A pilot study

BACKGROUND

Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) is a sensitive and specific tool in the risk stratification of pancreatic lesions, including cysts. The sensitivity and specificity of EUS-FNA has been shown to improve when cytology is combined with next-generation sequencing (NGS). Ideally, fresh cyst fluid is used for NGS. In this pilot study, we explore the possibility of sequencing DNA derived from residual alcohol-fixed pancreatic aspirates.

METHODS

Residual cytologic fixatives (n = 42) from 39 patients who underwent EUS-FNA for pancreatic lesions were collected along with demographics, imaging, and laboratory studies. Samples were designated as nonneoplastic/nonmucinous benign (NB), mucinous cyst (MC), pancreatic ductal adenocarcinoma (PDAC), or well-differentiated neuroendocrine tumor (NET) on the basis of cytopathologic evaluation and sequenced on the Oncomine platform (ThermoFisher Scientific, Waltham, Massachusetts).

RESULTS

Ten of 14 (71.4%) MCs exhibited clinically significant variants, including KRAS, GNAS, and TP53. Ten of 15 (66.7%) PDACs had KRAS alterations, and 9 of 15 (60%) showed variants in TP53. No variants were detected in any NETs. Only 1 of 9 (11.1%) NB aspirates showed variants in KRAS and MAP2K. Sequencing of formalin-fixed, paraffin-embedded tissue revealed variants identical to those detected in fixative-derived DNA in 4 of 5 cases (80%).

CONCLUSION

Residual DNA from alcohol-fixed aspirates are an underutilized source for NGS. Sequencing residual fixative-derived DNA has the potential to be integrated into the workup of pancreatic aspirates, possibly impacting management.

Acellular mucin in pseudomyxoma peritonei of appendiceal origin: what is adequate sampling for histopathology?

INTRODUCTION

Acellular intra-abdominal mucin is associated with a favourable prognosis in pseudomyxoma peritonei. There are no current guidelines on how many blocks are needed to classify the mucin as acellular with confidence.

METHODS

Specimens from cytoreductive surgery for mucinous appendiceal neoplasia, in which acellular mucin was found on initial histopathological examination, were prospectively identified. Additional tissue blocks were then taken to include either all residual visible intra-abdominal mucin or a maximum of 30 blocks. We also sent a questionnaire to pathologists in other centres.

RESULTS

Twelve patients were identified. In two cases, neoplastic epithelial cells were found on taking additional blocks. The questionnaire results suggested considerable variation in block-taking practice.

CONCLUSION

Taking additional tissue identified neoplastic cells in 2 of 12 cases. We recommend that sampling additional material should be considered when only acellular mucin is found on initial histology. Further work to determine the optimum sampling protocol is indicated.

Cytomegalovirus reactivation in inflammatory bowel disease: an uncommon occurrence related to corticosteroid dependence

Cytomegalovirus promotes mucosal injury in patients with inflammatory bowel disease, historically affecting 10-25% of ulcerative colitis patients with refractory disease. Viral reactivation is likely related to long-term corticosteroid therapy, which is no longer central to maintenance of patients with inflammatory bowel disease. We hypothesize that viral detection rates have decreased in the modern era, reflecting widespread use of immunomodulatory agents to control inflammation. We performed this study to evaluate the relationships between medical regimens and cytomegalovirus detection rates among patients with inflammatory bowel disease. We searched our database for all patients with established inflammatory bowel disease and severe flares diagnosed from 2002 to 2017. Patients maintained with corticosteroid therapy were considered to be corticosteroid-dependent and those treated with other agents were classified as corticosteroid-independent, provided they had not received corticosteroids within 6 months of colonoscopy. Biopsy samples were reviewed for viral inclusions and subjected to cytomegalovirus immunohistochemistry, and rates of viral detection were compared between groups. There were 135 corticosteroid-dependent patients; most had ulcerative colitis flares occurring during the 2002-2009 period. Patients with ulcerative colitis and Crohn disease were equally represented in the corticosteroid-independent group (n = 133) and most were evaluated for disease flares during the 2010-2017 interval. Cytomegalovirus was detected in 13 (8%) cases; 9 (69%) were diagnosed from 2002 to 2009 and all were obtained from corticosteroid-dependent patients (p = < 0.001). We conclude that rates of cytomegalovirus-related enterocolitis are declining among inflammatory bowel disease patients, reflecting a shift away from corticosteroid-based maintenance therapy in favor of more effective agents that do not promote viral reactivation.

Portal Cavernoma Cholangiopathy: Histologic Features and Differential Diagnosis

Objectives

Portal cavernoma cholangiopathy (formerly portal biliopathy) is a type of biliary injury that occurs in association with a portal vein thrombus or cavernoma. Although the radiographic features of portal cavernoma cholangiopathy have been enumerated in the literature, its histologic features have not been described in detail.

Methods

We describe the histologic findings in liver specimens from three patients with radiologically confirmed portal cavernoma cholangiopathy.

Results

Of the three patients, one underwent surgical resection due to a clinical suspicion for cholangiocarcinoma, one had a liver biopsy sample obtained for evaluation of possible cirrhosis, and one had a clinically suspicious "hilar mass" at the time of orthotopic liver transplant. Histologic features common among the three liver specimens included portal venous abnormalities, where the portal veins were obliterated or small relative to the portal tract size, and obstructive biliary changes, such as ductular reaction and reactive epithelial atypia accompanied by a mixed inflammatory cell infiltrate with neutrophils.

Conclusions

This case series provides clinicopathologic characteristics of portal cavernoma cholangiopathy. Histologic changes are reminiscent of hepatoportal sclerosis and/or bile duct obstruction. Attention to portal veins can provide helpful diagnostic clues, especially when biopsy samples are obtained from patients with a known portal vein thrombus or cavernoma.

Malformations, choristomas, and hamartomas of the gastrointestinal tract and pancreas

Congenital and hamartomatous lesions of the gastrointestinal tract cause diagnostic challenges for surgical pathologists. Many of these are merely histologic curiosities, whereas others have substantial clinical implications because they herald cancer syndromes or associated anomalies. Although a comprehensive discussion of all developmental abnormalities that can occur in the gastrointestinal tract is beyond the scope of a single manuscript, some entities are more likely to be encountered by surgical pathologists, have important clinical consequences, or pose diagnostic difficulties. The purpose of this review is to discuss the more common malformations and choristomas, as well as hamartomatous lesions that may be clinically important due to their risk for cancer development, frequent associations with heritable cancer syndromes and other anomalies, or potential to simulate other entities.

Assessing colorectal cancer mismatch repair status in the modern era: a survey of current practices and re-evaluation of the role of microsatellite instability testing

Results of DNA mismatch repair testing are used to detect Lynch syndrome and have prognostic and therapeutic implications among patients with sporadic colorectal carcinomas. Immunohistochemistry for mismatch repair proteins (MLH1, PMS2, MSH2, MSH6) and PCR for microsatellite instability are two established methods for assessing mismatch repair function. Older literature suggested a discordance rate of approximately 5% between these assays, leading some institutions to perform dual testing on all cases. Although universal mismatch repair testing is now recommended by multiple professional organizations, none provide guidelines regarding preferred assays. We surveyed 96 academic and nonacademic institutions to assess Lynch syndrome screening practices and evaluated discordance rates between immunohistochemistry and PCR among 809 colorectal cancers tested in our own institution. Our survey demonstrated no significant differences between academic and nonacademic practices with respect to testing strategies. Eighty six percent performed universal screening, and usually (76%) employed immunohistochemistry on initial biopsy samples. Only 20% employed PCR; these were mostly academic practices that used both immunohistochemistry and PCR (p < 0.01 compared with the nonacademic groups). Loss of MLH1/PMS2 staining was often (90%) followed by either BRAF mutational analysis or MLH1 methylation assays. Only 24% adhered to WHO recommendations to assign histologic grade based on mismatch repair status. We found only 3 cases (0.4%) with discordant immunohistochemistry and PCR results in our own practice: 1 reflected decreased MSH-6 staining in a neoadjuvantly treated microsatellite stable tumor, 1 MLH1-deficient tumor showed diminished MLH1/PMS2 in the tumor compared with internal control, and 1 case reflected an error in the molecular laboratory. Overall, our results showed extremely low discordance between methods assessing mismatch repair status and would suggest immunohistochemistry as the preferred single screening test. PCR can be reserved for cases that show equivocal immunostaining patterns.

Persistent Problems in Colorectal Cancer Reporting

Tumor stage, as determined by the Tumor, Node, Metastasis (TNM) staging system, is the single most influential factor determining treatment decisions and outcome among patients with colorectal cancer. Several stage-related elements in pathology reports consistently pose diagnostic challenges: recognition of serosal penetration by tumor (ie, pT3 vs pT4a), evaluation of regional lymph nodes, distinction between tumor deposits and effaced lymph nodes, and assessment of tumor stage in the neoadjuvant setting. This article discusses each of these issues in detail and provides practical tips regarding colorectal cancer staging.

Inflammatory and infectious manifestations of immunodeficiency in the gastrointestinal tract

Immune compromise may result from genetic abnormalities, HIV/AIDS, or consequences of therapy for neoplastic and autoimmune diseases. Many immunocompromised patients develop severe gastrointestinal symptoms, particularly diarrhea, accompanied by non-specific or mild endoscopic abnormalities; mucosal biopsy with pathologic interpretation has a major role in the diagnosis and management of these patients. Immunocompromised individuals are at risk for all the diseases that affect those with a healthy immune system, but they are also prone to other illnesses that rarely affect immunocompetent patients. This review discusses the gastrointestinal manifestations of primary and acquired immunodeficiency, chemotherapy-related injury, and infections that show a predilection for immunocompromised patients. Key histologic features and relevant differential diagnoses are emphasized.

Lymphocytic esophagitis: an update on histologic diagnosis, endoscopic findings, and natural history

Lymphocytic esophagitis is a histologic pattern of injury characterized by increased intraepithelial lymphocytes (>20/high-power field) with rare, or absent granulocytes. Lymphocytes tend to be more numerous in the peripapillary epithelium, and are often associated with evidence of mucosal injury, edema, and scattered dyskeratotic cells. More than a decade following its original description, lymphocytic esophagitis remains an enigmatic entity with variable clinical presentations, associated disorders, etiologies, treatment, and natural history. Most of the confusion regarding the clinical significance of this disorder stems from its diagnostic criteria: lymphocytic esophagitis is currently defined based entirely on histologic criteria, despite the common occurrence of lymphocytosis in a variety of unrelated inflammatory conditions of the esophagus. The goal of this review is to summarize the literature regarding lymphocytic esophagitis and focus on key clinicopathologic features that distinguish it from other esophageal disorders that can show increased numbers of intraepithelial lymphocytes.

Frozen Sections of the Liver

Intraoperative consultation requires skills in gross examination and histologic diagnosis, as well as an ability to perform rapid interpretations under time constraints. The aim of this review is to provide surgical pathologists with a framework for dealing with hepatic specimens in the frozen section area by covering common clinical scenarios and histologic findings. Differential diagnoses are considered in relation to primary hepatic neoplasia and metastatic diseases. Benign mimics of malignancy and other pitfalls in frozen section diagnosis of lesional tissue are covered. Finally, assessment of donor liver biopsy for organ transplant evaluation is discussed.

Findings in exudates can help distinguish benign gastric ulcers from ulcerated adenocarcinomas

AIMS

Most gastric carcinomas develop in association with mucosal atrophy and hypochlorhydria, whereas benign peptic ulcers are acid-related. Given that acid sterilises the gastric contents, we hypothesised that ulcerated gastric cancers may be associated with increased numbers of luminal microorganisms as compared with peptic ulcers, and that this feature may represent a helpful diagnostic clue to the presence of malignancy. We performed this study to determine whether the features of luminal debris, including microorganisms, from ulcerated gastric cancers were significantly different from those of debris associated with benign ulcers.

METHODS AND RESULTS

We retrospectively identified 50 ulcerated adenocarcinomas and 50 site-matched peptic ulcers. Luminal debris was evaluated for the nature of inflammation, necrosis, and the presence of mixed bacterial colonies or yeasts. Non-lesional mucosa was assessed for chronic gastritis, Helicobacter pylori, chemical gastropathy, and intestinal metaplasia. Patients in both groups were adults (mean age: 69 years and 62 years, respectively) with similar amounts of inflammation and cellular necrosis in biopsy material. However, 76% of ulcerated cancers harboured non-H. pylori bacterial colonies, as compared with only 22% of peptic ulcers (P < 0.01). Filamentous bacteria and fungi were highly specific for carcinoma (98% and P = 0.02 for both comparisons). Background intestinal metaplasia was more common among gastric cancers than among peptic ulcers (50% versus 26%, P = 0.02), whereas chemical gastropathy was more commonly associated with the latter (50% versus 10%, P < 0.01).

CONCLUSION

Gastric cancers may be colonised by non-H. pylori microorganisms. Detection of numerous bacterial colonies, filamentous bacteria or fungi in biopsy material obtained from ulcerated gastric lesions should raise suspicion for underlying malignancy.