Extra-appendiceal mucinous neoplasms: A tumour with clinicopathologic similarities to low- and high-grade appendiceal counterpart

AIMS

Appendiceal mucinous neoplasms feature neoplastic mucinous epithelium with pushing borders and densely fibrotic walls. We have identified five examples of analogous colorectal tumours.

METHODS AND RESULTS

Slides, pathology reports, and clinical data were reviewed. Whole genome sequencing was performed in two cases. Three were women and the mean age was 70. Associated GI conditions included Crohn's disease [1], diverticulosis [2], and sarcoma of the terminal ileum [1]. Signs/symptoms included obstruction [2], nausea, vomiting, abdominal pain [1], and positive faecal immunohistochemical test [1]. Colonoscopic findings included narrowing [1], "fullness" [1], and caecal lesion concerning for GIST [1]. Tumours involved the rectosigmoid [2], sigmoid [1], transverse colon [1], and cecum [1] and ranged from 1.5 cm to 8.5 cm. All but one tumour arose in the setting of faecal stream abnormalities related to obstruction, diverticulosis, or bowel diversion. All cases showed columnar, variably mucinous epithelium associated with little-to-no lamina propria. All but one case showed fibrosis of the submucosa. Three cases had high-grade areas. Neoplastic glands and/or mucin dissected through the muscularis propria or subserosa in 3 examples. No extracolonic neoplastic cells/mucin, infiltrative invasion, or desmoplastic response were identified. Three patients with available follow-up [5.5-28 months] are alive. Whole genome sequencing identified pathogenic TP53 and ERBB2 variants, as well as ERBB2 copy number amplification in one high-grade example.

CONCLUSIONS

Though these tumours share clinicopathologic characteristics with their appendiceal counterparts, our cohort is too small to draw solid conclusions. We propose the term "extra-appendiceal mucinous neoplasm [EAMN]" for these rare lesions.

Liver transplant for primary biliary tract neuroendocrine tumor in a nine-year-old girl

BACKGROUND

Neuroendocrine tumors (NETs) are rare epithelial neoplasms that arise most commonly from the gastrointestinal tract. In pediatrics, the most common site of origin is in the appendix, with the liver being the most common site of metastasis. Neuroendocrine tumors arising from the biliary tract are extremely rare.

METHODS

We describe a case of a nine-year-old girl who presented with obstructive cholestasis and was found to have multiple liver masses identified on biopsy as well-differentiated neuroendocrine tumor with an unknown primary tumor site.

RESULT

The patient underwent extensive investigation to identify a primary tumor site, including endoscopy, endoscopic ultrasound, and capsule endoscopy. The patient ultimately underwent definitive management with liver transplant, and on explant was discovered to have multiple well-differentiated neuroendocrine tumors, WHO Grade 1, with extensive infiltration into the submucosa of bile duct, consistent with primary biliary tract neuroendocrine tumor.

CONCLUSION

Identifying the site of the primary tumor in NETs found within the liver can be challenging. To determine if an extrahepatic primary tumor exists, workup should include endoscopy, EUS, and capsule endoscopy. Children with well-differentiated hepatic NETs, with no identifiable primary tumor, and an unresectable tumor, are considered favorable candidates for liver transplantation.

Abstract B026: Implicating SATB2 loss in a metaplasia-dysplasia sequence in human inflammatory bowel disease

Epithelial metaplasia, or the histologically evident replacement of one differentiated somatic cell type with another, offers insights into mucosal homeostasis as an adaptation to diverse inflammatory pathogenic stimuli. The cellular framework for metaplasia can be created by coordination of tissue-specific transcription factors (TFs) with epigenetic regulators of chromatin remodeling, allowing altered TF binding of inflammation-associated exposed genomic loci. For example, intestinal metaplasia (aberrant goblet cell differentiation and CDX2 expression, a pan-intestinal TF) is a common metaplastic response to chronic injury in the upper gastrointestinal tract, associated with increased risk of epithelial dysplasia and cancer. Inflammatory bowel disease (IBD) is an etiologically complex chronic inflammatory disease characterized by relapsing cycles of intestinal injury and healing. IBD patients carry increased risk of colitis-associated dysplasia and colorectal cancer (CAC) proportional to disease duration, extent, and severity. SATB2, or special AT-rich binding protein 2, is a chromatin organizing protein with homeostatic roles in osteoblastic, neural, and colonic differentiation. Intriguingly, others have recently shown that SATB2 is uniquely lost in human IBD dysplasia and CAC, in contrast to sporadic CRC where its expression is typically retained. (By contrast, CDX2 shows retained expression in both CAC and CRC.) Other recent work has shown that colon-specific Satb2 knockout in mice results in conversion of colon to small intestine, including emergence of villi and Paneth cells. Colonic mucosal biopsies from chronic IBD patients show histologic features reminiscent of small intestine with so-called Paneth cell metaplasia (PCM) and villiform, distorted growth. The molecular mediators of this epithelial remodeling in IBD are unknown. We hypothesized that SATB2 loss could result in a form of “small intestinal metaplasia” in human IBD colon. To investigate this, we selected a cohort of 20 IBD distal colon mucosal biopsies with marked crypt architectural changes and PCM and performed SATB2 immunostaining (n=7 Crohn’s disease, n=13 ulcerative colitis). Indeed, 19 of 20 such samples showed striking evidence of SATB2 loss. The pattern of SATB2 loss was heterogeneous; some tissue fragments showed complete epithelial loss as expected in small intestine, whereas others showed patchy loss in alternating crypts, even some showing heterogeneous expression within the same crypt. As positive and negative controls, we included normal distal colon and terminal ileum samples, observing expected intact and negative SATB2 expression, respectively. Of note, CDX2 was strongly expressed across the entire cohort, even in IBD tissue with loss of SATB2 expression. We propose that SATB2 loss is a pre-neoplastic metaplastic response to chronic injury in human colon. Future work will investigate how SATB2 loss enables a plasticity state permissive for emergence of TP53 mutations, dysplasia, and CAC.

Citation Format: Maged Zeineldin, Reem Abu-Shamma, Tatianna Larman. Implicating SATB2 loss in a metaplasia-dysplasia sequence in human inflammatory bowel disease [abstract]. In: Proceedings of the AACR Special Conference on Colorectal Cancer; 2022 Oct 1-4; Portland, OR. Philadelphia (PA): AACR; Cancer Res 2022;82(23 Suppl_1):Abstract nr B026.

Centriole signaling restricts hepatocyte ploidy to maintain liver integrity

Hepatocyte polyploidization is a tightly controlled process that is initiated at weaning and increases with age. The proliferation of polyploid hepatocytes in vivo is restricted by the PIDDosome-P53 axis, but how this pathway is triggered remains unclear. Given that increased hepatocyte ploidy protects against malignant transformation, the evolutionary driver that sets the upper limit for hepatocyte ploidy remains unknown. Here we show that hepatocytes accumulate centrioles during cycles of polyploidization in vivo. The presence of excess mature centrioles containing ANKRD26 was required to activate the PIDDosome in polyploid cells. As a result, mice lacking centrioles in the liver or ANKRD26 exhibited increased hepatocyte ploidy. Under normal homeostatic conditions, this increase in liver ploidy did not impact organ function. However, in response to chronic liver injury, blocking centriole-mediated ploidy control leads to a massive increase in hepatocyte polyploidization, severe liver damage, and impaired liver function. These results show that hyperpolyploidization sensitizes the liver to injury, posing a trade-off for the cancer-protective effect of increased hepatocyte ploidy. Our results may have important implications for unscheduled polyploidization that frequently occurs in human patients with chronic liver disease.

Familial Adenomatous Polyposis-associated Traditional Serrated Adenoma of the Small Intestine: A Clinicopathologic and Molecular Analysis

Familial adenomatous polyposis (FAP) is an inherited cancer predisposition syndrome associated with numerous gastrointestinal tract adenomatous polyps, as well as gastric fundic gland polyps and pyloric gland adenomas in the upper gastrointestinal tract. While colonic FAP-associated traditional serrated adenomas (TSAs) have been reported in a few studies, small bowel FAP-associated adenomas with TSA morphology have not been characterized. This study describes the clinicopathologic and molecular findings of this type of adenoma in the small bowel of patients with FAP. We reviewed small bowel adenomas in 45 consecutive FAP patients to identify adenomas with zones showing slit-like serrations, cells with eosinophilic cytoplasm, ectopic crypt formation, and vesicular nuclei. Sporadic small bowel adenomas from 51 consecutive patients were also reviewed for adenomas with the same features. Of the 177 polyps from 45 FAP patients and 60 polyps from 51 nonsyndromic patients, 18 TSAs from 9 FAP patients (20%) and 10 TSAs from the sporadic group (19.6%) were identified. FAP patients presented at a younger age than nonsyndromic patients (median: 43 vs. 66; P=0.0048). FAP-associated TSAs were asymptomatic and smaller than sporadic TSAs (median size: 0.6 vs. 2.5 cm; P=0.00006). Immunostaining for β-catenin and testing for BRAF and KRAS mutations were performed in a subset of the cohort. Nuclear β-catenin was seen in 1 FAP-associated TSA and 3 nonsyndromic TSAs. All TSAs (FAP-associated and nonsyndromic) showed wild-type BRAF, while KRAS mutations were identified only in the nonsyndromic setting. In summary, small bowel FAP-associated and sporadic TSAs share a similar morphology, and the BRAF-serrated pathway does not contribute to their pathogenesis.

836 Murine fecal microbiota transfer models colonize human microbes selectively and reveal transcriptional pathways associated with response to neoadjuvant checkpoint inhibitors

Background

Human gut microbial species found to associate with clinical responses to immune checkpoint inhibitors (ICIs) are often tested in murine models using fecal microbiota transfer (FMT), wherein tumor responses in recipient mice may recapitulate human responses to ICI treatment. However, many FMT studies have reported only limited methodological description, including identification of colonizing species associated with murine outcomes, details of murine cohorts, and statistical methods. Thus, the reproducibility and robustness of ICI murine models remain uncertain.

Methods

To investigate gut microbial species that impact ICI responses, we performed human to germ-free (GF) mouse FMT using pre-treatment stools from a pathologic lung cancer responder (R) and a pathologic lung cancer non-responder (NR) after neoadjuvant anti-PD-1 and anti-CTLA4 treatment, followed by implantation of the mice with syngeneic tumors and anti-PD-L1 treatment. Cohorts of GF mice varied by sex, age and syngeneic cell line implanted. To identify relevant microbes, murine tumor progressors (MT-P) and non-progressors (MT-NP) to anti-PD-L1 were classified based on tumor growth curves, 16S rRNA sequencing of human and mouse stools was performed, and data was statistically corrected for mouse characteristics using a generalized linear model. RNA sequencing was performed to assess transcriptional changes in murine tumors.

Results

R-FMT mice yielded a greater anti-tumor response in combination with anti-PD-L1 treatment compared to NR-FMT, although the magnitude varied depending on the mouse cell line, sex, and individual experiment. Microbiota analysis revealed a shared presence of the most highly abundant taxa between the human inocula and mice, however low abundance human taxa colonized mice more variably after FMT. Multiple Clostridium species correlated with tumor outcome in individual anti-PD-L1-treated R-FMT mice. RNAseq analysis revealed differential expression of T cell and NK cell-related pathways in responding tumors, irrespective of FMT source, and enrichment of these cell types were confirmed by immunohistochemistry.

Conclusions

This study identifies several human intestinal microbial species that may play a role in clinical responses to ICIs and suggests attention to biological variables is needed to improve reproducibility and limit variability across experimental murine models.

Ethics Approval

All studies in this abstract have been approved by Johns Hopkins University Animal Care and Use and Johns Hopkins Medicine Institutional Review Board.

Gastrointestinal Malakoplakia: Clinicopathologic Analysis of 26 Cases

Malakoplakia is an inflammatory process related to defective macrophage response to bacterial infection. To further characterize the clinicopathologic manifestations of gastrointestinal malakoplakia, 26 cases were identified from 6 institutions. Hematoxylin and eosin-stained slides and available stains were reviewed, and pertinent clinicopathologic features analyzed. Sixteen patients were women (62%). Mean patient age was 64 (range: 24 to 83). Sites included the colorectum (n=23), appendix (n=1), and stomach (n=2). Clinical indications for tissue procurement included screening (n=14), tumor resection (n=5), diarrhea (n=1), adenoma surveillance (n=1), ulcerative colitis flare (n=1), abdominal pain (n=1), and appendicitis (1). All cases featured histiocytes with abundant, pale, eosinophilic cytoplasm focally containing Michaelis-Gutmann bodies. The process frequently involved the mucosa (n=19), with architectural distortion in 13 cases. Lymphoid aggregates were present in 18 cases, which were prominent or obscuring in 11 (all colon biopsies) and provoked concern for lymphoma in 2. Associated findings included adenocarcinoma (n=5), adenoma (n=2), gastric hyperplastic polyps (n=1), chemical gastritis (n=1), collagenous colitis (n=1), and active chronic colitis (n=2). In cases with available stains, Michaelis-Gutman bodies were highlighted by Periodic Acid-Schiff with diastase, Von Kossa, and iron stains. Although 2 cases were positive for Tropheryma whipplei antibody, no T. whipplei transcripts were detected on real-time polymerase chain reaction. All patients with available follow-up are alive and well with no additional instances of malakoplakia. Malakoplakia of the gastrointestinal tract is a benign, incidental finding. Although histologic features in the stomach and colon resections are similar to those at other sites, exuberant lymphocytic response in colon biopsies and immunoreactivity with T. whippleii antibody may provoke initial confusion and lead to unnecessary time and resource investment.

Gastric mucosal devitalization (GMD): translation to a novel endoscopic metabolic therapy

Background and study aims  The metabolic effects of bariatric surgery may partially result from removal of the gastric mucosa, an often underappreciated endocrine organ. Using argon plasma coagulation (APC), we may be able to selectively devitalize (ablate) the mucosa. The aim of this study was to identify the optimal tissue color that would correspond to selective gastric mucosal devitalization (GMD) using ex-vivo human stomach specimens. Patients and methods  Stomach specimens were obtained at sleeve gastrectomy. Prior to APC application, a submucosal fluid cushion was created. APC was then applied over a 2 × 2-cm area to the fundus and body, aiming for the three indicator colors (white, golden, brown). Pathological analysis was then performed independently and in a blinded fashion by two pathologists to determine the depth of mucosal and submucosal percent thermal injury and mucosal percent cell death. Results  Six patients were enrolled. There was a significant correlation between tissue color and mucosal percent thermal injury. The highest percent mucosal thermal injury was seen with brown (99.6 %, 95 % CI: 98.7, 100), followed by golden (92.5 %, 95 % CI: 85.5, 99.5), and then white (75.2 %, 95 % CI: 58.3, 92.1, P  < 0.01). Submucosal thermal injury was seen in 88.9 % of the slides. Greater than minimal submucosal injury (> 10 % depth) was found significantly more with brown tissue color (91.6 %) than golden (75 %) or white (33.3 %, P  < 0.05). However, 91.7 % of the entire sample set < 50 % injury. Conclusion  GMD is achievable using APC without thermal injury to muscularis propria. A golden color results in sufficient mucosal injury with only superficial injury to the submucosa.

Hypophysitis Secondary to Cytotoxic T-Lymphocyte-Associated Protein 4 Blockade: Insights into Pathogenesis from an Autopsy Series

Hypophysitis that develops in cancer patients treated with monoclonal antibodies blocking cytotoxic T-lymphocyte-associated protein 4 (CTLA-4; an inhibitory molecule classically expressed on T cells) is now reported at an incidence of approximately 10%. Its pathogenesis is unknown, in part because no pathologic examination of the pituitary gland has been reported to date. We analyzed at autopsy the pituitary glands of six cancer patients treated with CTLA-4 blockade, one with clinical and pathologic evidence of hypophysitis, one with mild lymphocytic infiltration in the pituitary gland but no clinical signs of hypophysitis, and four with normal pituitary structure and function. CTLA-4 antigen was expressed by pituitary endocrine cells in all patients but at different levels. The highest levels were found in the patient who had clinical and pathologic evidence of severe hypophysitis. This high pituitary CTLA-4 expression was associated with T-cell infiltration and IgG-dependent complement fixation and phagocytosis, immune reactions that induced an extensive destruction of the adenohypophyseal architecture. Pituitary CTLA-4 expression was confirmed in a validation group of 37 surgical pituitary adenomas and 11 normal pituitary glands. The study suggests that administration of CTLA-4 blocking antibodies to patients who express high levels of CTLA-4 antigen in the pituitary can cause an aggressive (necrotizing) form of hypophysitis through type IV (T-cell dependent) and type II (IgG dependent) immune mechanisms.

Epidural spinal compression as an initial presentation of Hodgkin lymphoma

Classical Hodgkin lymphoma (CHL) commonly arises in lymph nodes and initial presentation with extranodal disease is rare. We report a patient who presented with progressively worsening back pain, lower extremity weakness and numbness concerning for a myelopathic process of uncertain etiology. MRI revealed an epidural soft tissue mass with cord displacement, for which she underwent resection. Histological analysis of the surgical specimen demonstrated CHL. Further investigation revealed an anterior mediastinal mass, consistent with spread from a more typical location.