Testicular Rosai-Dorfman disease clonally related to CMML - Case report and literature review.

BACKGROUND: Rosai-Dorfman disease (RDD), a rare form of non-Langerhans cell histiocytosis with heterogenous clinical features, arises from precursor cells that give rise to cells of the histiocytic and monocytic lineages. An association with hematological neoplasms has been reported. Testicular RDD is rarely described, with only 9 reported cases in the literature. Genetic data to assess clonal relationships between RDD and other hematological neoplasms remain scarce. We describe an instance of testicular RDD against a background of chronic myelomonocytic leukemia (CMML), with genetic studies in both neoplasms. CASE PRESENTATION: A 72-year-old patient with a history of CMML sought evaluation of growing bilateral testicular nodules. Solitary testicular lymphoma was suspected; orchidectomy was performed. The diagnosis of testicular RDD was established morphologically and confirmed immunohistochemically. Molecular analysis of testicular lesions and of archived patient bone marrow revealed the KRAS variant c 0.35 G>A / p.G12D in both, suggesting a clonal relationship. CONCLUSION: These observations support classifying RDD as a neoplasm that can be clonally related to myeloid neoplasms.

Colorectal resection in endometriosis patients: correlation between histopathological findings and postoperative outcome.

INTRODUCTION: Endometriosis is associated with a high number of chronic pelvic pain and reduced quality of life. Colorectal resections in case of bowel involvement of endometriosis are associated with an unneglectable morbidity in young and healthy patients. There is no linear correlation established between the degree of symptoms and stage of endometriosis. The aim of this study was to correlate the histological findings to preoperative pain scores in colorectal resected patients with endometriosis. METHODS: Twenty-five patients who underwent laparoscopic colorectal resection for endometriosis between 2014 and 2019 were included in this retrospective study. Pain level was assessed preoperatively and postoperatively via phone call in May 2020. Histopathology was correlated to preoperative symptoms and postoperative outcome. RESULTS: Average follow-up time was 38.68 months (± 19.92). Preoperative VAS-score was 8.32 (± 1.70). We observed a significant reduction of pain level in all patients after surgery (p ≤ 0.005). Pain levels were equal regarding the presence of satellite spots and various degrees of infiltration depth. The resection margins were clear in all patients. Postoperative complications occurred in 6 cases (24%) and anastomotic leakage was observed in 3 patients (12%). Average VAS-score at time of follow-up was 1.70 (± 2.54). CONCLUSION: Our data demonstrate that adequate colorectal resection leads to reduction of pain and an increase of quality of life irrespective of histopathological findings. An experienced team is necessary to improve intraoperative outcome and to reduce postoperative morbidity in case of complication.

Clinically high-risk breast cancer displays markedly discordant molecular risk predictions between the MammaPrint and EndoPredict tests.

Inter-test concordance between the MammaPrint and the EndoPredict tests used to predict the risk of recurrence in breast cancer was evaluated in 94 oestrogen receptor-positive, HER2-negative breast cancers. We correlated histopathological data with clinical risk estimation as defined in the MINDACT trial. 42.6% (40/94) of cases were high-risk by MammaPrint, 44.7% (42/94) by EndoPredict (EPclin), and 45.7% (43/94) by clinical risk definition. Thirty-six percent of genomic risk predictions were discordant with a low inter-test correlation between EndoPredict and MammaPrint (p = 0.012; κ = 0.27, 95% CI [0.069, 0.46]). Clinical risk stratification did not correlate with MammaPrint (p = 0.476) but highly correlated with EndoPredict (p < 0.001). Consequently, clinically high-risk tumours (n = 43) were more frequently high-risk by EndoPredict than by MammaPrint (76.6% vs. 46.5%, p = 0.004), with 44% of cases discordantly classified and no significant association between genomic risk predictions (p = 0.294). Clinicians need to be aware that clinical pre-stratification can profoundly influence multigenomic test performance.

Primary intestinal lymphangiectasia in an adult patient: A case report and review of literature.

BACKGROUND: Primary intestinal lymphangiectasia (PIL), first described in 1961, is a rare disorder of unknown etiology resulting in protein-losing enteropathy. The disease is characterized by dilatation and leakage of intestinal lymph vessels leading to hypoalbuminemia, hypogammaglobulinemia, and lymphopenia. Since the severity and location of lymph vessels being affected can vary considerably, the range of associated symptoms is wide from mild lower-limb edema to generalized edema, abdominal and/or pleural effusion, and recurrent diarrhea, among others. Although usually developing in early childhood, we present the case of a 34-year-old woman with PIL. Moreover, we performed a literature review systematically assessing clinical presentation, and provide a practical approach to facilitate diagnosis and therapy of PIL in adults. CASE SUMMARY: Our patient presented with unspecific symptoms of abdominal discomfort, fatigue, nausea, and recurrent edema of the lower limbs. Interestingly, a striking collinearity of clinical symptoms with female hormone status was evident. Additionally, polyglobulia, hypoalbuminemia, hypogammaglobulinemia, and transient lymphocytopenia were evident. Due to suspicion of a bone marrow disease, an extensive diagnostic investigation was carried out excluding secondary causes of polyglobulinemia and hypoalbuminemia. The diagnosis of primary intestinal lymphangiectasia was established after 22 wk by histological analysis of biopsy samples obtained via enteroscopy. Consecutively, the patient was put on a high-protein and low-fat diet with medium-chain triglycerides supplementation leading to significant improvement of clinical symptoms until 2 years of follow-up. CONCLUSION: PIL can be the reason for cryptogenic hypoalbuminemia, hypogammaglobulinemia, and lymphopenia in adulthood. Due to difficulty in correct diagnosis, treatment initiation is often delayed despite being effective and well-tolerated. This leads to a significant disease burden in affected patients. PIL is increasingly been recognized in adults since the majority of case reports were published within the last 10 years, pointing towards an underestimation of the true prevalence. The association with female hormone status warrants further investigation.

Incidence of extramural venous invasion in colorectal carcinoma as determined at the invasive tumor front and its prognostic impact.

Extramural venous invasion (EMVI) is prognostic for colorectal cancer; however, veins are only detected partially by normal perpendicular preparation. Therefore, reported findings are conflicting and standardization is required. A total of 239 resection specimens were examined by tangential preparation of the extramural veins at the invasive tumor front. Average follow-up was 39 months. The relationship of EMVI to metachronous hematogenic metastasis (MHM) was evaluated. With this method, a high prevalence of EMVI beginning in stage II is apparent. In stage I, 66% of patients with EMVI developed MHM; in stage II, 25%; and in stage III, 49%. In stage III, the number of tumor-invaded veins is crucial. In the absence of detection of EMVI, MHM occurred in 1 of 29 patients in stage II and in 2 of 13 patients in early stage III. By tangential sectioning at the invasive tumor front, we found a high incidence of EMVI beginning in stage II, which increases with tumor stage. Especially in stages II and III, the correct determination of absent EMVI has a high negative predictive value for MHM. In stage I, EMVI defines a patient group with increased risk for MHM. The quantification of EMVI is an important issue for standardization.

Clinicopathologic Features and Prognostic Impact of Lymph Node Involvement in Patients With Breast Implant-associated Anaplastic Large Cell Lymphoma.

Breast implant-associated anaplastic large cell lymphoma (BI-ALCL) is a rare T-cell lymphoma that arises around breast implants. Most patients manifest with periprosthetic effusion, whereas a subset of patients develops a tumor mass or lymph node involvement (LNI). The aim of this study is to describe the pathologic features of lymph nodes from patients with BI-ALCL and assess the prognostic impact of LNI. Clinical findings and histopathologic features of lymph nodes were assessed in 70 patients with BI-ALCL. LNI was defined by the histologic demonstration of ALCL in lymph nodes. Fourteen (20%) patients with BI-ALCL had LNI, all lymph nodes involved were regional, the most frequent were axillary (93%). The pattern of involvement was sinusoidal in 13 (92.9%) cases, often associated with perifollicular, interfollicular, and diffuse patterns. Two cases had Hodgkin-like patterns. The 5-year overall survival was 75% for patients with LNI and 97.9% for patients without LNI at presentation (P=0.003). Six of 49 (12.2%) of patients with tumor confined by the capsule had LNI, compared with LNI in 8/21 (38%) patients with tumor beyond the capsule. Most patients with LNI achieved complete remission after various therapeutic approaches. Two of 14 (14.3%) patients with LNI died of disease compared with 0/56 (0%) patients without LNI. Twenty percent of patients with BI-ALCL had LNI by lymphoma, most often in a sinusoidal pattern. We conclude that BI-ALCL beyond capsule is associated with a higher risk of LNI. Involvement of lymph nodes was associated with decreased overall survival. Misdiagnosis as Hodgkin lymphoma is a pitfall.

Melanocytic naevi with perineurial differentiation: a distinctive variant of neurotised naevi and a diagnostic pitfall with desmoplastic melanoma.

AIMS: Spindle cell differentiation is not an uncommon finding in common acquired naevi, and may represent a form of neurotisation with Schwannian differentiation of melanocytes. Perineurial differentiation in this context appears to be very rare, and is only poorly documented in the literature. We therefore aimed to study this rare form of neurotisation in melanocytic naevi more comprehensively. METHODS AND RESULTS: We have identified six melanocytic tumours showing spindle cell morphology and perineurial differentiation from routine and referral material. Clinical data and follow-up were obtained, and the histological and immunohistochemical features were analysed. The tumours affected middle-aged adults (median, 48 years; range, 26-74 years), with a wide anatomical distribution and benign follow-up (median, 13 months; range, 6-48 months). All tumours were nodular and circumscribed but asymmetrical, with extension into the deep dermis and superficial subcutis. A characteristic finding was a biphasic growth pattern with a lentiginous compound naevus in the superficial aspect and abrupt transition to a prominent nodular spindle cell proliferation in the deeper reaches. Spindle cells were bland and uniform, and arranged singly and in short fascicles in a loose fibromyxoid stroma. In areas, a whorled arrangement of slender spindle cells with wavy nuclei was seen. Distinctive intratumoral hypocellular nodules and peripheral lymphoid aggregates were additional features. By immunohistochemistry, the spindle cells were mainly S100-positive melanocytes. In areas, S100-negative/epithelial membrane antigen-positive spindle cells showing coexpression of Glut-1 and claudin-1 were closely admixed. CONCLUSION: This perineurial differentiation probably represents a rare and unusual form of neurotisation. The tumours are benign but may be mistaken for desmoplastic melanoma. Awareness of and careful attention to the clinicopathological and immunohistochemical features allow reliable separation.

MammaPrint versus EndoPredict: Poor correlation in disease recurrence risk classification of hormone receptor positive breast cancer.

INTRODUCTION: Correct risk assessment of disease recurrence in patients with early breast cancer is critically important to detect patients who may be spared adjuvant chemotherapy. In clinical practice this is increasingly done based on the results of gene expression assays. In the present study we compared the concordance of the 70-gene signature MammaPrint (MP) with the 12 gene assay EndoPredict (EP). METHODS: Representative tissue of 48 primary tumours was analysed with the MP during routine diagnostic purposes. Corresponding formalin-fixed, paraffin-embedded tissue was thereafter analysed by the EP test. Risk categories of both tests were compared. RESULTS: 41 of 48 tumours could be directly compared by both tests. Of the 17 MP low risk cases, only 9 were considered low risk by EP (53% agreement) and of the 24 MP high risk cases, 18 were high risk by EP (75% agreement). Discrepancies occurred in 14 of 41 cases (34.1%). There was only a weak and non-significant correlation between the MP and EP test with an overall concordance of only 66%. The original therapeutic recommendation was based on the MP and would have been changed in 38% of the patients following EP test results. 4 patients developed distant metastases. The respective tumours of these patients were all classified as high risk by the EP, but only 3 were classified as high risk by the MP. CONCLUSION: Both tests resulted in different treatment recommendations for a significant proportion of patients and cannot be used interchangeably. The results underscore the urgent need for further comparative analyses of multi-genomic tests to avoid misclassification of disease recurrence risk in breast cancer patients.

Paternal chronic colitis causes epigenetic inheritance of susceptibility to colitis.

Inflammatory bowel disease (IBD) arises by unknown environmental triggers in genetically susceptible individuals. Epigenetic regulation of gene expression may integrate internal and external influences and may thereby modulate disease susceptibility. Epigenetic modification may also affect the germ-line and in certain contexts can be inherited to offspring. This study investigates epigenetic alterations consequent to experimental murine colitis induced by dextran sodium sulphate (DSS), and their paternal transmission to offspring. Genome-wide methylome- and transcriptome-profiling of intestinal epithelial cells (IECs) and sperm cells of males of the F0 generation, which received either DSS and consequently developed colitis (F0(DSS)), or non-supplemented tap water (F0(Ctrl)) and hence remained healthy, and of their F1 offspring was performed using reduced representation bisulfite sequencing (RRBS) and RNA-sequencing (RNA-Seq), respectively. Offspring of F0(DSS) males exhibited aberrant methylation and expression patterns of multiple genes, including Igf1r and Nr4a2, which are involved in energy metabolism. Importantly, DSS colitis in F0(DSS) mice was associated with decreased body weight at baseline of their F1 offspring, and these F1 mice exhibited increased susceptibility to DSS-induced colitis compared to offspring from F0(Ctrl) males. This study hence demonstrates epigenetic transmissibility of metabolic and inflammatory traits resulting from experimental colitis.

First clinical experiences using a new in-bag morcellation system during laparoscopic hysterectomy.

INTRODUCTION: Endoscopic techniques have successfully reduced the invasiveness of hysterectomy, when compared to open procedures. Power morcellation, as a part of the minimal invasive concept, carries the risk of disseminating cells from the tissue specimen. The present observational study reports on first experiences using a new system (More-Cell-Safe, A.M.I., Austria) for contained in-bag morcellation during laparoscopic hysterectomy. MATERIALS AND METHODS: The dual opening system allows two-port access without bag puncture. The optic is protected against spread cell contamination with a disposable sleeve. Application data were prospectively recorded on the first n = 7 consecutive patients and compared to n = 7 preceding patients undergoing uncontained morcellation. RESULTS: Bag system use was surgically successful in 6 of 7 cases (85.7 %). Morcellated specimen weight ranged from 205 to 638 g (mean 413.33 ± 176.85; median 413). In one patient, the uterine specimen (1050 g) proved too large to be placed into the bag. Average time associated to the bag use was 16.2 ± 7.65 min, ranging from 8.5 to 26.5 min (median 14 min). Removed bags contained bloody fluid with residual tissue fragments weighing overall between 21 and 85 g. Spread spindle cells were detected in two cases after uncontained morcellation, but not after in-bag morcellation. CONCLUSION: The experiences from our small pilot series prove technical feasibility in the clinical setting.

Enteric nervous system α-synuclein immunoreactivity in idiopathic REM sleep behavior disorder.

OBJECTIVE: To investigate the expression of α-synuclein in colonic biopsies of patients with idiopathic REM sleep behavior disorder (iRBD) and address if α-synuclein immunostaining of tissue obtained via colonic biopsies holds promise as a diagnostic biomarker for prodromal Parkinson disease (PD). METHODS: Patients with iRBD, patients with PD, and healthy controls were prospectively recruited to undergo colonic biopsies for comparison of α-synuclein immunoreactivity patterns between the groups by using 2 different antibodies. RESULTS: There was no difference in colonic mucosal and submucosal immunostaining between groups using the 15G7 α-synuclein antibody, which was found in almost all participants enrolled in this study. By contrast, immunostaining for serine 129-phosphorylated α-synuclein (pSyn) in submucosal nerve fibers or ganglia was found in none of 14 controls but was observed in 4 of 17 participants with iRBD and 1 out of 19 patients with PD. CONCLUSIONS: The present findings of pSyn immunostaining of colonic biopsies in a substantial proportion of iRBD participants raise the possibility that this tissue marker may be a suitable candidate to study further as a prodromal PD marker in at-risk cohorts.

A new in-bag system to reduce the risk of tissue morcellation: development and experimental evaluation during laparoscopic hysterectomy.

INTRODUCTION: Minimal invasive approaches have proven beneficial for patients undergoing myomectomy and hysterectomy, but necessary tissue morcellation carries the risk of cell dissemination in rare cases of inadvertent malignancy. Performing the morcellation process within a contained bag system may prevent spilling and therefore enhance safety of the laparoscopic procedures. MATERIAL AND METHODS: The present study describes the development and experimental evaluation of a new bag system in vitro and in vivo in a pig model of laparoscopic supracervical hysterectomies. RESULTS: The main results on n = 8 procedures with in-bag morcellation compared to n = 8 controls without bag indicate reproducible feasibility and protective effect of the new bag, which is the first published to our knowledge that does not require puncturing in a standard multiport laparoscopy setting. Overall surgery time was significantly prolonged in the bag group by 12.86 min (P = 0.0052; 95 % confidence interval 4.64-21.07), but peritoneal washings were negative for muscle cells in all cases with bag use, compared to positive cytology in 5/8 cases without bag (P = 0.0256). CONCLUSION: Clinical trials will now be necessary to investigate the reproducibility of these encouraging data in human application.

Tumor budding in colorectal cancer revisited: results of a multicenter interobserver study.

Tumor budding in colorectal cancer (CRC) is recognized as a valuable prognostic factor but its translation into daily histopathology practice has been delayed by lack of agreement on the optimal method of assessment. Within the context of the Swiss Association of Gastrointestinal Pathology (SAGIP), we performed a multicenter interobserver study on tumor budding, comparing hematoxylin and eosin (H&E) with pan-cytokeratin staining using a 10 high power field (10HPF) and hotspot (1HPF) method. Two serial sections of 50 TNM stage II-IV surgically treated CRC were stained for H&E and pan-cytokeratin. Tumor buds were scored by independent observers at six participating centers in Switzerland and Austria using the 10HPF and 1HPF method on a digital pathology platform. Pearson correlation (r) and intra-class correlation coefficients (ICC) comparing scores between centers were calculated. Three to four times more tumor buds were detected in pan-cytokeratin compared to H&E slides. Correlation coefficients for tumor budding counts between centers ranged from r = 0.46 to r = 0.91 for H&E and from r = 0.73 to r = 0.95 for pan-cytokeratin slides. Interobserver agreement across all centers was excellent for pan-cytokeratin [10HPF: ICC = 0.83 and 1HPF: ICC = 0.8]. In contrast, assessment of tumor budding on H&E slides reached only moderate agreement [10HPF: ICC = 0.58 and 1HPF: ICC = 0.49]. Based on previous literature and our findings, we recommend (1) pan-cytokeratin staining whenever possible, (2) 10HPF method for resection specimens, and (3) 1HPF method for limited material (preoperative biopsy or pT1). Since tumor budding counts can be used to determine probabilities of relevant outcomes and as such more optimally complement clinical decision making, we advocate the avoidance of cutoff scores.

Verrucous carcinoma of the endometrium: a rare and challenging diagnosis.

Verrucous carcinoma of the endometrium is an exceedingly rare disease with only a few cases reported in the literature. We describe the case of a 68-year-old postmenopausal patient who presented with vaginal discharge. PAP smears were repeatedly reported negative and an endometrial curettage 2 years prior to the diagnosis only showed fragments of benign squamous epithelium. Because of continuous symptoms a hysterectomy was performed and revealed extensive squamous metaplasia of the endometrium with focal transition to verrucous carcinoma. This case demonstrates that benign appearing squamous epithelium in curettage specimens, especially when abundant, is not necessarily ordinary portio epithelium. In this setting, the clinical presentation becomes paramount for considering a well differentiated squamous carcinoma of the endometrium and avoiding diagnostic delay.

Holes in gastric mucosa in upper gastrointestinal endoscopy.

Gastritis cystica profunda (GCP) is a rare disease that shows multiple cystic gastric glands dispersed within the submucosa of the stomach. GCP occurs most commonly in patients who have undergone previous gastric surgery and presents as subepithelial tumor or a polypoid lesion. Here, we report the case of GCP in a 79-year-old patient who had undergone Billroth II gastric resection. During upper gastrointestinal endoscopy multiple lesions like tiny holes in the mucosa were observed. Endoscopic ultrasound showed cystic structures in the gastric submucosa. Biopsies finally proved the dispersed mucosal glands in the submucosa, which are pathognomonic for GCP. So far, in all published cases, GCP presented as polypoid lesions with no mucosal damage in upper gastrointestinal endoscopy. It is for the first time that GCP has been diagnosed with cystic lesions connected to the gastric lumen with a porus in each of the cysts.

Type I interferon signalling in the intestinal epithelium affects Paneth cells, microbial ecology and epithelial regeneration.

OBJECTIVE: Intestinal epithelial cells (IECs) at the internal/external interface orchestrate the mucosal immune response. Paneth cells secrete antimicrobial peptides and inflammatory mediators, protect from pathogens and shape the commensal microbiota. Prompted by the genetic association of the locus harbouring the type I interferon (IFN) receptor (IFNAR1) with Crohn's disease, and a transcriptional signature for type I IFN signalling in Paneth cells, we studied the function of IFNAR1 in IECs. DESIGN: Type I IFN signalling was studied in mice with conditional deletion of Ifnar1 in IECs. Phenotype was characterised at baseline, and gut microbiota composition was assessed by 16S rDNA ribotyping. The role of IFNAR1 was also investigated in experimental colitis induced by dextran sodium sulfate (DSS) and colitis-associated cancer induced by DSS in conjunction with azoxymethane (AOM). RESULTS: Ifnar1(-/-(IEC)) mice displayed expansion of Paneth cell numbers and epithelial hyperproliferation compared with Ifnar1-sufficient littermates. While Ifnar1(-/-(IEC)) mice did not exhibit spontaneous inflammation or increased severity in DSS colitis compared with Ifnar1(+/+(IEC)) mice, they exhibited an increased tumour burden in the AOM/DSS model. Both hyperproliferation and tumour promotion were dependent on the microbial flora, as the differences between genotypes were marked upon separately housing mice, but disappeared when Ifnar1(-/-(IEC)) and Ifnar1(+/+(IEC)) mice were co-housed. Accordingly, ribotyping revealed marked differences between Ifnar1(-/-(IEC)) and Ifnar1(+/+(IEC)) mice that where diminished upon co-housing. CONCLUSIONS: IFNAR1 in IECs, and Paneth cells in particular, contributes to the regulation of the host-microbiota relationship, with consequences for intestinal regeneration and colitis-associated tumour formation.

Interactions of human peritoneal mesothelial cells with serous ovarian cancer cell spheroids--evidence for a mechanical and paracrine barrier function of the peritoneal mesothelium.

BACKGROUND: Ovarian carcinoma spreads by implantation of tumor cells onto the peritoneal mesothelium. We established a 3-dimensional coculture model to simulate the interactions of ovarian carcinoma cell aggregates with human peritoneal mesothelial cells (HPMC). METHODS: Multicellular tumor spheroids (MCTS) of the human ovarian cancer cell line SK-OV-3 were directly inoculated onto either confluent HPMC monolayers or their submesothelial matrix or were cocultured with mesothelium without direct cellular contact. RESULTS AND DISCUSSIONS: Inoculation of MCTS onto submesothelial matrix resulted in rapid attachment (within 30 minutes) of the tumor cell aggregates followed by rapid dissemination (within 12 hours) and growth of tumor cells. Intact mesothelium increased the time required for MCTS attachment (up to 180 minutes) and led to almost complete inhibition of tumor cell dissemination and to 47% tumor growth suppression. Bromodeoxyuridine incorporation into tumor cell nuclei was almost completely abolished in cocultured MCTS. Growth also was inhibited in MCTS treated with supernatants of HPMC. Analysis of coculture supernatants revealed that HPMC-derived transforming growth factor ß (TGF-ß) was almost completely bound by MCTS. Addition of a function-blocking anti-TGF-ß antibody (30 µg/mL) to the cocultures abrogated the growth inhibitory effect of the mesothelium by 50%. CONCLUSIONS: The present model provides a dynamic system to study the complex interactions of ovarian carcinoma cells with HPMC over extended periods and suggests that the mesothelium constitutes a mechanical and partly TGF-ß-mediated paracrine barrier to the progression of ovarian cancer.

ER stress transcription factor Xbp1 suppresses intestinal tumorigenesis and directs intestinal stem cells.

Unresolved endoplasmic reticulum (ER) stress in the epithelium can provoke intestinal inflammation. Hypomorphic variants of ER stress response mediators, such as X-box-binding protein 1 (XBP1), confer genetic risk for inflammatory bowel disease. We report here that hypomorphic Xbp1 function instructs a multilayered regenerative response in the intestinal epithelium. This is characterized by intestinal stem cell (ISC) expansion as shown by an inositol-requiring enzyme 1α (Ire1α)-mediated increase in Lgr5(+) and Olfm4(+) ISCs and a Stat3-dependent increase in the proliferative output of transit-amplifying cells. These consequences of hypomorphic Xbp1 function are associated with an increased propensity to develop colitis-associated and spontaneous adenomatous polyposis coli (APC)-related tumors of the intestinal epithelium, which in the latter case is shown to be dependent on Ire1α. This study reveals an unexpected role for Xbp1 in suppressing tumor formation through restraint of a pathway that involves an Ire1α- and Stat3-mediated regenerative response of the epithelium as a consequence of ER stress. As such, Xbp1 in the intestinal epithelium not only regulates local inflammation but at the same time also determines the propensity of the epithelium to develop tumors.