ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 an increased chromogranin expression was found in our series. Occasionally, neuroendocrine hyperplasia within the adenomas can be observed. Nevertheless, data does not suggest a higher probabil- ity of existence of neuroendocrine tumours in adenomas associated with FAP. PS-07-052 Spasmolytic polypeptide-expressing metaplasia as a marker for gastric cancer risk prediction S. Mozgovoi*, M. Stepanchenko, A. Gubanova, M. Parygina, J. Fedotova, M. Livzan *Omsk State Medical University, Russia Background & objectives: Assessment of chronic atrophic gastritis is the key factor in gastric cancer preventing strategy. Spasmolytic polypeptide-expressing metaplasia (SPEM) can be indicated as possible marker of extensive gastric atrophy with following association of gastric cancer development. Methods: Resection specimens (n=30) from patients who had gas- trectomy due to invasive gastric adenocarcinoma were obtained, processed routinely, stained with H&E. Pseudopyloric metaplasia (PPM) was recognised as antral-type glands in oxyntic mucosa. Microarray method was used to prepare specimens for IHC. Tissue specimens were stained with MUC6, TFF2 and pepsinogen-1 (PG- 1) antibodies to reveal either PPM or SPEM accordingly. Results: Widespread (involving 4-5 glands) PPM was detected in 14 cases. In 9 cases single (3-4 glands) areas were determined, in 7 cases pseudopyloric metaplasia wasn’t detected. Foci of metaplas- tic changes were distributed as follows: PMM sites were found at distance of 4-7 cm from the border of invasive tumour. In 3 cases, a combination of epithelial dysplasia, intestinal metaplasia, and PPM was determined. Expression of PG-1 was found in 12 cases, in 1 case expression was artificial. TFF2+ glands were determined in 21 cases, including sites nearest to dysplasia foci. SPEM foci were designated as a part of true pyloric metaplasia (PPG-1 - ) and pseudopyloric metaplasia (PPG-1 +) . Conclusion: Distribution of PPM wasn’t perifocal as expected, but found mostly at the distant zone of adenocarcinoma, although in some cases was nearby dysplasia foci. The expression of TFF2 and PG-1 didn’t always overlap and not all PPM glands could be considered a SPEM. The significance of these findings is yet to be understood, but recognising pseudopyloric/SPEM metaplasia in biopsy specimens could potentially help clinicians to reveal patients with considerably higher risk for gastric cancer. PS-07-053 Concurrent loss of MLH1, PMS2 and MSH6 immunoexpression in gastrointestinal cancer indicating a widespread dysregulation in DNA reparation processes N. Reitsam*, S. Dintner, A. Probst, D. Vlasenko, J. Enke, B. Märkl, B. Grosser *General Pathology and Molecular Diagnostics, University Hospi- tal of Augsburg, Germany Background & objectives: DNA mismatch repair proteins func- tion as heterodimers (MLH1/PMS2; MSH2/MSH6), usually result- ing in deficiency in one subsystem in microsatellite instable can- cers. As the involvement of both subsystems is unusual, we aim to shed light on the molecular basis of this phenomenon. Methods: We retrospectively analysed gastrointestinal can- cers that underwent immunohistochemical testing for deficient DNA mismatch repair proteins during the last four years in our hospital to identify cases with a simultaneous deficiency in MLH1/PMS2 and MSH2/MSH6. To understand this unusual phenomenon, we performed further molecular testing (MSI- PCR, MLH1 promotor and/or BRAF status) and next-generation sequencing focusing on genes related to DNA reparation. Results: In the cohort, we could identify 103 cases with defi- cient DNA mismatch repair proteins. In nearly all cases only one mismatch repair heterodimer - either MLH1/PMS2 or MSH2/MSH6 - was affected. However, five cases showed a con- current loss of MLH1/PMS2 and MSH6. Whereas some cases seem to be sporadic with a MLH1 promotor hypermethylation and/or BRAF V600E mutation, we also could detect potential germ line mutations. Importantly, next-generation sequencing indicates that the concurrent loss of MLH1/PMS2 and MSH6 expression is associated with a dysregulation in DNA reparation as all of these cases showed additional mutations in genes cod- ing for proteins like ATM, BRCA2, BARD1, CHEK1, FANCA, PALB2, RAD54L and RAD51D. Conclusion: Our study suggests that the simultaneous loss of MLH1, PMS2 and MSH6 immunoexpression among different gastrointesti- nal cancers is associated with and potentially even based on more widespread alterations in DNA repair processes. Next-generation sequencing could reveal further mutations in additional DNA repair- related genes in the present cases. With the advent of drugs targeting DNA repair in clinical practice, especially PARP-inhibitors, and their potential indication extension for mutations other than BRCA1/2 such as PALB2 our results are of immediate clinical significance. PS-07-054 Intestinal spirochetosis: clinicopathological features of 22 year experience in a single institution A. Pasco Peña*, M. Mercado, A. Larrea, C. Cerezo, C. Fuertes, I. Amat, A. Cordoba *Hospital Universitario de Navarra, Spain Background & objectives: Intestinal spirochetosis (IS) is an infre- quent infection and its clinical significance in individual cases has remained unclear as their association with other diseases. We report the clinicopathological features of the patients diagnosed in our hospital in a 22 years experience. Methods: Retrospective and descriptive study from the patients with a diagnosis of intestinal spirochetosis from 2000-2021 in We histologically reviewed paraffin-embedded section slides made from 2000 to 2021at Navarras University Hospital. Clinical records were reviewed for each one of the patients for epidemiological features, treatment and follow up. Results: We identified 29 cases of IS. Median age was 48 years old (25 - 76 years old). 79% were males. In 69% of the patients an endoscopic ultrasound was performed due to gastrointestinal symptoms. The most common symptom was diarrhoea (44, 8%). 27, 6% of the patients were asymptomatic. 17,2% were in the colorectal cancer screening program. 48,3% of the patients were treated with antibiotic (metronidazole). 24,1% of the patients were HIV positive. Transverse colon was the most common localisation (37,9%), 24,7% of the patients had more than one affected colonic segment. Six patients (20,7%) had an associated polyp (3 tubular adenomas, 2 hyperplastic polyps and one juvenile polyp). Conclusion: Intestinal spirochetosis is more frequent in young population and in male homosexuals. It presents as a symptomatic disease in immunosupresed patients and is very rare symptomatic in other the population except in children. The most common symp- tom is diarrhoea. Patients treated with antibiotics had a favourable outcome. The most common localisation was the transverse colon, but it can affect other colonic segments even in a discontinuous S105