ECP 2023 Abstracts

S196 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 spindled cells with blunt-ended nuclei and eosinophilic cytoplasm. Although focal nuclear atypia was observed, necrosis and mitotic activ- ity were not detected. On immunohistochemical study, all five cases were positive for SMA and desmin. The main differential diagnosis is with GIST, which may exhibit similar morphological features. How- ever, KIT (CD117) was negative in all five cases. Conclusion: Digestive leiomyoma is an uncommon gastrointestinal mesenchymal tumour. Given their rarity and inherent complexity, accu- rate diagnosis can be challenging. The combination of morphologi- cal, immunophenotypic, and molecular findings is the best strategy to confirm the diagnosis and promote the most appropriate therapeutic approach. E-PS-06-012 Study of the associations between tumour budding in primary gas- tric cancer and clinico-pathological parameters E. Benammou*, D. Bacha, I. Mallek, S. Gharbi, M. Hajri, H. Mestiri, A. Lahmar, S. Ben Slama *Department of Pathology, Armand Trousseau Hospital-Sorbonne University, France Background & objectives: Tumour budding (TB) is the presence of a cluster of l<5 carcinoma cells at the tumour invasion front. We aim to investigate the prognostic value of TB in gastric adenocarcinoma (ADK), which remains controversial, and its association with the usual prognostic markers. Methods: This retrospective study, conducted at the Department of Pathology of Mongi-Slim University Hospital, includes 68 patients operated for gastric ADK over a period extending from January 2008 to December 2017. TB was classified into grade1 (0-4 buds); grade2 (5-9 buds) and grade3 (≥10 buds). Additionally, a two-grade classi- fication was applied with low-grade (<10 buds) and high-grade (≥10 buds) TB. Results: The sex ratio=2.57 with a mean age of 61.34 years. The ADK was papillary in 4 patients (6%), tubular in 27 patients (40%), mucinous in 6 patients (9%), poorly cohesive in 25 patients (36%) and mixed in 6 patients (9%). TB was grade 1 in 35 patients (51%), grade 2 in 12 patients (18%) and grade 3 in 21 patients (31%). It was low-grade in 69% of cases and high-grade in 31%. A significant cor- relation was noted between the presence of TB and poorly differenti- ated ADK (p=0.035), vascular emboli (p=0.006), perinervous invasion (p=0, 038), parietal infiltration (p=0.003), lymph node involvement (p=0.005), metastases (p=0.015), advanced tumour stage (p=0.014) and metastatic recurrence (p=0.033). High-grade TB was predictive of poor 5-year overall survival (p=0.007) and poor 5-year recurrence-free survival (p=0.02). Conclusion: In gastric ADK, the standardization of TB assessment is essential in routine practice for inclusion in standardized reports to assist in the therapeutic management of patients. E-PS-06-013 GATA3 positivity in oesophageal squamous cell carcinoma I. Blazquez*, J. Martínez, E. Dorca, M. Gómez, M. Guerrero, M.J. Paules Villar *Hospital Universitari de Bellvitge, Spain Background & objectives: GATA3 is an excellent diagnostic marker for breast and urothelial carcinoma. Our study aimed to investigate the incidence of GATA3 expression in oesophageal squamous cell carci- noma (SCC) and its significance with respect to histological features, clinical parameters and overall survival. Methods: Immunohistochemical expression of GATA3 was evaluated in 53 patients diagnosed with oesophageal SCC at our institution dur- ing 2015-2017. The percentage of GATA3-positive tumour nuclei was scored as well as staining intensity, which was rated as negative (0), weak (1+), moderate (2+) or strong. We collected clinical data and follow-up. Results: Mean age of diagnosis was 68 years (range 51-88 years). Male predominance (n=43). Most patients exhibited advanced disease at diagnosis (39/53 stage III-IV). Median survival of 12 months. 42/53 cases were moderately differentiated (Grade 2), 6/53 poorly differen- tiated (G3) and 5/53 well differentiated (G1). 16/53 cases (30.19%) showed GATA3 positivity, (weak positivity 11/16; moderate 5/16). When analysing OS using Kaplan-Meyer curves, a trend towards reduced survival was noticed in GATA3+ subgroup although statisti- cal significance was not reached (Logrank p=0.12, mean OS: 19.81 vs 20.6 months respectively). Moreover, GATA3 positivity was associated with a higher histological grade. Conclusion: We believe that GATA3 could be a prognostic factor for overall survival; however, our data were not statistically significant as the series is limited, and studies with larger numbers of cases are needed. E-PS-06-014 GLI-1 rearranged gastric tumour or gastroblastoma C. Bongrain*, N. Guedj, G. Pierron, A. Sauvanet, D. Cazals-Hatem *Beaujon Hospital, France Background & objectives: The gastroblastoma, first described by Miettinen et al. in 2009, has been individualized in the 2019 WHO Classification as a biphasic epithelial-mesenchymal gastric tumour with MALAT1::GLI1 fusion gene. Here, we report an observation and relate it with previous similar cases. Methods: A 28-years-old patient presented a 4 cm pyloric well-limited obstructive tumour developed in the submucosa. The resection showed an epithelioid proliferation made of regular ovoid cells arranged in nests or adenoid lobules without obvious spindle inflexion. Cytokera- tin, CD56, and focally CD10 were expressed; the Ki67 proliferation index was estimated at 2%. Results: Molecular analysis revealed an ACTB::GLI1 fusion transcript. The patient presented no recurrence after 40 months of follow-up. To date, 20 “gastroblastomas” have been reported in the literature, 7 of them with confirmed GLI fusion transcript (MALAT1::GLI1 in six, PTCH1::GLI2 in one). Three of them presented a local recur- rence and/or metastasis after a mean follow-up of 50 months [8-100], underlining the need for long-term surveillance. The novel GLI1 gene fusion partner described in our case was reported in similar tumours with predominant mesenchymal differentiation called “pericytoma with t[7;12]” or “plexiform fibromyxoma”, one of them located in the jeju- num, the others in soft tissue. Conclusion: Gastroblastoma is part of the new family of GLI1- rearranged enteric mural tumours which shares a peculiar histology (biphasic differentiation), a common phenotype (variable expression of cytokeratin and CD56) and probably an indolent course. Hence, we pro- pose that all novel tumours with GLI1 fusion gene should be collected and followed for defining the long-term behaviour of such neoplasms. E-PS-06-015 Appendiceal actinomycosis: a case series with clinical, radiologic and histopathologic correlation M. Bronte Anaut*, E. Carracedo Vega, J. Arredondo Montero, A.S. De Oliveira Gomes, I. Amat *Hospital Universitario Araba, Spain Background & objectives: Abdominal actinomycosis is an infrequent chronic infection caused by Actinomyces israelii. Appendiceal actino- mycosis is a highly uncommon pathology, with isolated reports in the literature to date. Methods: A search was made in our institution’s archives and 3 patients with a diagnosis of appendiceal actinomycosis were identified.