ECP 2023 Abstracts

S70 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 and non-recurrent (n=37) cases (based on evidence of early endoscopic POR, Rutgeerts score >i2 on colonoscopy <15 months after resec- tion) revealed differences in median adipocyte flattening (p=0.045) and median capacity fractal dimension (p=0.006). Conclusion: AI provides an objective and in-depth assessment of PIRMs. Based on our findings, elevated neutrophil density in stroma/ muscle might be a novel risk factor for time-to-POR. High count and small size of Paneth cell granules, less flattened adipocytes and low fractal dimension in submucosal fat were observed in digital slides from high-risk PIRMs. Our results suggest that digitized H&E PIRM slides can be used to predict early and time to POR. Validation of these findings, currently in progress, is warranted. Funding: A grant from The Leona M. and Harry B. Helmsley Charitable Trust. PS-03 | Poster Session Electron Microscopy PS-03-001 Understanding the quality of your electron microscopy provider in this era of outsourcing of services. T. de Haro* *UK NEQAS - CPT, United Kingdom Background & objectives: Electron Microscopy remains vital to the diagnostic repertoire for the diagnosis of pathologies. A large amount of EM is now outsourced to units away from the originating trust so how can you ensure your EM provider is fit for purpose? Methods: Methods of evaluating the following were considered. Results: To ensure that the EM service you are sending your samples to is ‘fit for purpose’ Conclusion: Access to EM services remains vital but is increasingly being outsourced to units remote from the originating trust. here, the pathologist is reliant on the images and ultrastructural report being accurate to inform diagnosis. To ensure accuracy, the EM unit should participate in a quality EQA scheme and the staff should be experienced and educated to a high level in ultrastructural pathology. Without this the referring trust cannot be guaranteed the service they are paying for is fit for purpose. PS-04 | Poster Session Head and Neck Pathology PS-04-001 Tumour-infiltrating lymphocytes in oral cavity squamous cell carcinoma and its association with clinicopathological parameters S. Ahuja*, A.A. Khan, S. Zaheer *Department of Pathology, Vardhman Mahavir Medical College and Safdarjung Hospital, New Delhi, India Background & objectives: Oral squamous cell carcinomas (SCC) is one of the most common cancers of the head and neck region. The aim of the present study is to evaluate the significance of tumour-infiltrating lymphocytes (TILs) in oral squamous cell carcinoma. Methods: All patients of oral cavity SCC who underwent resection were included in the study. Assessment of the stromal TILs was done on H&E-stained sections using the International Immuno-Oncology Biomarker Working Group scoring criteria. TILs were categorised as low TILs (<20%) and high TILs (>=20%). The association between TILs and clinicopathological parameters was evaluated using the Fis- cher exact test. Results: Among the 51 cases evaluated in the present study, major- ity (76.4%) were <60 years of age. 48 patients (94.1%) were males while the remaining (5.9%) were females. In the oral cavity, the most frequently involved sites included buccal mucosa and tongue. Moder- ately differentiated squamous cell carcinomas were the most prevalent according to grade. Low and high TILs were found in 25.5% and 74.5% cases respectively. TILs were found to show a significant association with tumour size and lymphovascular invasion. However, no significant association was found with age, gender, nodal status, grade, perineural invasion and site in the oral cavity. Conclusion: The evaluation of TILs as proposed by the International Immuno-Oncology Biomarker Working Group is an simple, inexpen- sive test. Morphological evaluation of TIL can provide valuable prog- nostic information in oral cavity squamous cell carcinoma cases and can be incorporated as a part of routine histopathological reporting. PS-04-004 ETV6::NTRK3 translocation- associated papillary adenocarci- noma: let’s play it by ear D. Bell*, E. Maghami, R. Bakkar, M. Afkhami *City of Hope National Cancer Center, Department of Pathology, USA Background & objectives: Ceruminous glands are modified apocrine glands, situated in the external auditory canal (EAC), that, together with sebaceous glands, produce cerumen. The neoplastic transforma- tion of these structures is very rare. We encounter 2 cases of EAC adenocarcinoma with ETV6::NTRK3 fusion. Methods: Index case 1 73 years old female with admitting diagnosis of cellulitis of external ear canal. Diagnostic excisional biopsy submitted for expert opinion. Index case 260 years old male with intermittent bloody otorrhea and ear pain. CT films EAC tumour invading TMJ and extending into parotid. Diagnostic biopsy submitted for expert opinion. Results: Histologically, a papillary glandular pattern was common to both biopsies. The neoplastic cells were diffusely positive for keratins AE1/AE3, Cam5.2 (#1), CK7 (#2),SOX10, scattered p63 (#1); both biopsies were negative for neuroendocrine markers and S100; DOG1, AR (#1); Ki-67 15% (#1) and 60% (#2). Molecular genetic testing using targeted next-generation sequencing (NGS) with solid tumour comprehensive platform targeting DNA (523 genes panel) to detect SNVs, CNV, MSI and TMB; and RNA sequencing platform (165 gene panel) to detect fusion with unknown gene partners was performed. A fusion ETV6::NTRK3 was detected in both cases. Despite this genetic overlap, the morphology and immunophenotype delineate its clear separation from secretory carcinoma. Conclusion: These cases demonstrate novel primary EAC adenocar- cinoma with papillary morphology, which expand the ever-increasing list of ETV6::NTRK3-positive malignancies and which we would like to term ETV6::NTRK3-translocation associated papillary adenocarcinoma. We also advocate the use of molecular techniques in rare tumours of uncertain type or differentiation, to increase understanding and pos- sibilities of reproducible classification of these rare neoplasms. Pathologists and oncologists should recognize this entity, which leads to a direct approach for detecting NTRK fusion for appropriate treatment. PS-04-005 Addition of tumour microenvironment immune cell composition to conventional prognostic factors improves the performance of a locoregional recurrence predictive model for oral squamous cell carcinoma S. Bisheshar*, M.F. van der Kamp, J. de Vries, L. Slagter-Menkema, E. Schuuring, G.A. Lunter, G.B. Halmos, B. van der Vegt *Department Pathology and Medical Biology, University Medical Center Groningen, The Netherlands