ECP 2023 Abstracts

S193 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 analysed their association with clinicopathological data and survival rates. Results: The expressions of PD-L1, CD73, A2ar and CTLA-4 in CRC were all higher than those in adenoma and non-neoplastic specimens. In cancer cells, expression levels of PD-L1, CD73 and A2ar were positively correlated. High PD-L1 expression was associated with advanced tumour stage, and low density of tumour-infiltrating lympho- cytes (TILs). High CD73 expression was significantly correlated with high tumour grades, and lymph node metastasis. High A2ar expression was significantly correlated with high tumour grades. In TILs, low CTLA-4 expression was associated with advanced tumour stage and increased number of positive LNs. Multivariate Cox regression analy- sis showed that PD-L1 and CD73 expression were independent predic- tors for overall survival and recurrence-free survival, respectively. Conclusion: The findings of this study highlight the impact of these immune checkpoint molecules as mediators of tumour progression and their potential as predictors of prognosis in CRC. These biomark- ers may be used to better stratify patients with CRC with respect to prognosis and personalized treatment plans. The combination of two or more therapeutic options targeting these molecules may be a new breakthrough in CRC management. E-PS-06-002 Colonic tubular adenoma with clear cell changes: a case report and review of literature S. Al-Dandan*, O. Alzallal, H. Khushaim, W. AlShakweer *King Fahad Medical City/King Fahad Hospital Hofuf, Saudi Arabia Background & objectives: Clear cell change is rare in colorectal tubular adenomas and adenocarcinomas. To date, only eighteen cases have been reported in the English literature. We aimed to highlight this unique pathologic entity and review the previously published reports. Methods: A 67-year-old female with a history of breast cancer, mas- tectomy, and hormonal therapy had a sigmoid colon polyp during a screening colonoscopy. The polyp measured 0.8 cm in maximum dimension, located 30.0 cm proximal to the anus, and was removed with a cold snare. Results: Histopathological examination of the polyp demonstrated a tubular adenoma with low-grade dysplasia and prominent cytoplasmic clearing. The clear cytoplasm was negative for Periodic Acid-Schiff (PAS) and Mucicarmine stains. Immunohistochemically, the clear cells were positive for CK20 and CDX2 and negative for CK7, indicating their intestinal origin/lineage. The nuclear reactivity towards Beta- Catenin and p53 and the high Ki67 proliferative activity (70%) further confirmed the dysplastic nature of these clear cells. The adenomatous glands were mismatch repair (MMR) protein-proficient with a retained expression of MLH1, PMS2, MSH2, and MSH6. Conclusion: The aetiology of clear cell change in tubular adenomas of the colorectum is poorly understood, and the pathology remains incompletely characterized. Both CD10 and CEA (monoclonal and polyclonal) showed a pattern of reactivity similar to the previously described cases in the literature. The expression of CD10 may sug- gest small intestinal phenotype/differentiation. The higher prolifera- tive activity and cytoplasmic localization of CEA expression in the clear cell component of the adenoma may indicate a greater malignant potential. E-PS-06-003 Clear cell change in colonic adenomas: a rare histopathological finding F. Almarii*, A. Iorgescu, C. Stroescu, D. Pietrareanu, V. Herlea *Fundeni Clinical Institute, Centre of Excellence in Translational Med- icine, Fundeni, University of Medicine and Pharmacy "Carol Davila" Bucharest, Romania Background & objectives: Clear cell change in colonic polyps is a rare finding, characterized by the presence of clear cells within the adenoma- tous epithelium. This morphologic alteration has been reported in various other benign and malignant tumours, less frequently in colonic adenomas. Methods: We present the case of a 53 y.o. male diagnosed and treated in Fundeni Clinical Institute, Bucharest. The patient was previously treated for a colonic adenocarcinoma and during the control colo- noscopy, another polyp was discovered at 10 cm of the anal orifice, and polypectomy was performed. Gross examination revealed a semi- pedunculated 3 × 2.5 ×1.5-cm tan polyp with friable surface. Results: The H&E slides revealed an adenomatous polyp with tub- ulo-villous architecture and focal high-grade dysplasia. There were also areas with a distinct morphology, with frequent empty vacuoles, some of them subnuclear, reminiscent of the foetal variant of lung adenocarcinoma, and some areas with clarification of the whole cyto- plasm. The vacuoles were negative for PAS staining. On Immunohistochemistry the clear area showed diffuse positivity for CDX2, positive CK20 expression, intense cytoplasmic and membranous staining for CEAm and it was negative for CK7, Glypican 3 and AFP. The final diagnosis was of a rectal adenoma with tubular architec- ture and focal high-grade dysplasia and the clear cell change was only shortly described. Conclusion: Clear cell change in colonic adenomas is a rare histo- pathological finding that can pose diagnostic challenges. The precise clinical implications of clear cell change in colonic adenomas are not well-established, and its impact on the behaviour and malignant poten- tial of the adenomas remains unclear. Further studies are needed to determine whether clear cell change represents a distinct histopatho- logical subtype of colonic adenomas, with unique biological and clini- cal characteristics. E-PS-06-004 Increasing incidence of colorectal serrated lesions and polyps in the Danish population 2000 - 2021 M. Andrea*, R. Karlin Jepsen, T. Plato Kuhlmann *Department of Pathology, Herlev and Gentofte Hospital, Denmark Background & objectives: Colorectal serrated lesions and polyps (SP) include hyperplastic polyps (HP), sessile serrated lesions -/+ dysplasia (SSL/SSL-D), and traditional serrated adenomas (TSA). 20-30% of colorectal adenocarcinomas develop from SP. We present incidence and baseline characteristics of SP in a Danish cohort. Methods: We used The Danish Pathology Registry to include all SP in the Danish population from January 1st, 2000 to December 31st, 2021. Based on the unique Danish personal identification number and SNOMED-codes, combined with the age and sex of patients, and date of surgery, we determined the incidence of the SP subtypes, anatomical location, and changes over time. Results: In the period 2000-2021, a total of 292 761 SP were removed from 163 949 patients: SSL: 50 702, SSL-D: 5 959, HP: 224 860, TSA: 10 293. The median age was 64.1 years [55.2-71.6] and 53.3% were male. We found a general increase of SP from 2 804 in 2000 to 25 846 in 2021. The proportion of SSL increased from 1.1% (81) in 2006 to 38% (9 891) in 2021. HP and TSA were most frequent in the rectum and the sigmoid colon, while SSL and SSL-D occurred most often in the ascending colon and the sigmoid colon, followed by the remaining parts of the right colon. Conclusion: During the study period 2000-2021, we find an increasing number of SP, especially SSL. From 2019-2021 the number of SP seem to stabilize, while the proportion of SSL keeps rising. Essential factors most likely influencing the number of SP are the introduction of the Danish National Colorectal Cancer Screening Program in 2014 and the new WHO classification of SP in 2019. This study will form the basis for future studies on SP as an important precursor of colorectal cancer.