ECP 2023 Abstracts

S63 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Conclusion: BC Molecular subtypes from IHC and Prosigna show limited concordance in Luminal tumours, suggesting that Ki67 and especially PR used for IHC classification might be reconsidered when approaching LA and LB diagnosis. Precise Ki67 labelling remains an important biomarker in spite its lim- ited reproducibility. More research in these parameters is requested in order to better under- stand the correlation between both methods in breast pathology. PS-01-025 Atlas of ex vivo breast tissue and carcinomas images by ultra-fast large field-of-view fluorescence confocal microscopy of lumpectomy M. Mathieu*, M. Ragazzi, P. Van Diest, M. Ferchiou, O. Casiraghi, N. Labaied, A. Conversano, M. Abbaci *Gustave Roussy, Université Paris-Saclay, France Background & objectives: New generation ultra-fast fluorescence confocal microscopy (UFCM) allows ex-vivo intraoperative analysis of fresh breast tissue. Objective: To create an atlas of ex vivo UFCM images of breast tis- sues and carcinomas based on large field-of-view UFCM breast cancer images. Methods: One hundred sixty patients who underwent breast con- serving surgery were included. Their fresh surgical specimens were sectioned, stained with acridine orange and imaged with large-field- of-view UFCM. The resulting images were digitally false coloured in purple gradient. Each UFCM image was correlated with the cor- responding definitive histology. The images of normal tissue, inflam- mation, benign and cancer lesions have been collected. Results: UFCM images in a quality closely resembling frozen sec- tions were recorded from 103 invasive carcinoma (58 no special type, 44 lobular, 1 mucinous), 49 carcinomas in situ (47 ductal, 2 lobular) and 8 specimens without cancer. The UFCM image corresponds to a large-section histology and allows the evaluation of the global archi- tecture of the tissue at low and intermediate magnification and could then be zoomed in at higher magnifications to identify cellular fea- tures. With an axial resolution of 30 μm, UFCM images were richer in cells than histological sections. Representative images of the normal, non-tumoral and carcinomatous tissues were annotated to establish an UFCM atlas and will be available online. Conclusion: UFCM enables the fast imaging of fresh breast surgical specimens. Main morphological criteria defined in traditional histopa- thology such as tissue architecture and cell features can be applied to describe UFCM images content. However, the cell density is higher than in histological sections and needs training. The created atlas of the main normal or tumoral tissues could become a reference for the introduction of the technique for intraoperative UFCM examination of breast speci- mens. Further studies will introduce more rare breast lesions. Funding: Samantree Medical PS-01-026 Association of serum inflammatory profiles with breast cancer immunophenotypes and clinicopathological factors Y.G. Montoyo Pujol*, S. Pascual-García, P. Martínez-Peinado, A.B. López-Jaén, J. Ponce, I. Lozano, T. Martín-Bayón, H. Ballester, A. Ramos, S. Delgado, E. Castellón-Mollá, J.M. Sempere-Ortells, G. Peiró *Alicante Institute for Health and Biomedical Research (ISABIAL), Spain Background & objectives: Inflammation can inhibit tumorigenesis. However, maintaining serum cytokines (SC) in breast cancer (BC) is linked to immunosuppression, tumour growth, metastasis, and drug resistance. Therefore, our objective was to evaluate the relationship between clinicopathological factors and SC in BC. Methods: We collected serum from 229 pretreated BC patients (17.9% Luminal A, 17.9% Luminal B/HER2, 17.9% Luminal B/HER2+, 10.4% HER2-enriched, 17.9% Triple-Negative/Basal-like -TN/BL-) and 50 healthy donors (HD). Using LEGENDplex immunoassay, we measured 62 SC through flow cytometry. The results were correlated with clin- icopathological factors (age, tumour size and grade, vascular invasion, necrosis, immunophenotype, tumour-infiltrating lymphocytes (TILs), lymph-node status, and Ki67). Results: Compared to HD, BC patients had higher levels of SCF, MIP3α, VEGF, and EPO but lower levels of PDGF-AA, Galectin-9, PDGF-BB, and MCP-1, IL-2RA, IL-18, IL-8, B7.2, IL-27, MIP-1β, IL-11, IL-1β, and PD-1. Moreover, EPO correlated with younger age (p<0.001), in contrast to Galectin-9, MCP-1, IL-2RA, B7.2, MIP1β, and IL-8 (p≤0.013). IL-27 was elevated in tumours ≤20mm (p=0.043) and, along with B7.2 and IL-1β, in low Ki67 tumours (p≤0.044). Con- trary, MIP-3α was associated with a high Ki67% (p=0.022). Increased PDGF-BB, MIP3-α, and MIP-1β were detected in non-Luminal tumours (p≤0.049), but only EPO in Luminal ones (p=0.046). Conclusion: Our results showed that BC patients had a specific profile of SC compared to HD. This profile differs among BC immunophe- notypes, with IL-27, B7.2, and IL-1β on the one hand and MIP-3α on the other, being associated with favourable and unfavourable clinico- pathological features, respectively. Supported by Grant (SEAP-Proyecto Semilla; Expt. 200042); Biobank HGUA (21-154) and HUB-ICO-IDIBELL (PT17/0015/0024). PS-01-027 HER2-Low breast cancer: incidence and observer variability F. Ramalhosa*, G. Fontinha, S. Bárbara, C. Faria, R. Celestino, M.A. Cipriano, M.J. Martins *Centro Hospitalar e Universitário de Coimbra, Portugal Background & objectives: Human Epidermal Growth Factor Receptor 2 (HER2) status is a biomarker in breast cancer for therapeutic stratifica- tion and prognosis. Recent trials showed favourable results when using Trastuzumab Deruxtecan in previously treated HER2-low advanced breast cancers. Methods: HER2 status of diagnostic core biopsies of breast invasive carcinomas from 2020 and 2021 in a central university hospital was reviewed to estimate the incidence of HER2-low breast cancer. 20 ran- domly picked cases were blindly assessed by two breast expert patholo- gists and two residents to evaluate observer variability. Results: A total of 421 diagnostic core biopsies were observed. The HER2 status at the time of diagnosis was analysed: 150 negative 0 (35.7%), 132 low 1+ (31.3%), 66 equivocal (15.7%); 73 positive 3+ (17.3%). The blind assessment by two breast expert pathologists and two resi- dents showed a concordance of 50% in the HER2 status determination. When only the experts were considered the concordance rose to 65%. The lowest concordance - 22.2% and 40% - were found in low 1+ (9 cases) and negative 0 (5 cases), while the positive 3+ cases showed a higher concordance (75% in 4 cases). Conclusion: The results of HER2 status at the time of diagnosis in our institution are roughly equivalent to what is found in the literature. The HER2-low corresponds to one-third of the total cases that are, now, potentially treated by Trastuzumab Deruxtecan. The implementation of software support for HER2 status determination is essential since the interobserver variability is high, particularly in HER2 negative 0 and HER2-low cases. This work had the financial support of AstraZeneca Portugal. PS-01-028 Clinicopathological spectrum of adenomyoepithelioma: a tertiary care cancer centre experience of a rare entity A. Sahay*, M. Aziz, A. Patil, T. Shet, S. Desai *Tata Memorial Center, Mumbai, India