ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 mutation frequencies, with significant proportions occurring out- side of the known hotspot regions; analysis is ongoing for prognos- tic value combined with clinical data. Similar mutational profiles of primary and relapse tumours suggest invariability through treat- ment and may thus aid in utilizing diagnostic tools for therapeutic response prediction. Moreover, similar and alternating mutations of the tumours can be further investigated for incorporation of future mutation-targeted treatments. Funding: This trial is a non-interventional study set up as a research collaboration between Karolinska Institutet and Novartis Sweden AB. OFP-10-013 Breast carcinoma with apocrine differentiation: less indolent than expected? C. Rossi*, S. Fraticelli, E. Boveri, G. Di Giulio, M. Fanizza, B. Francesco, A. Sgarella, A. Ferrari, A. Della Valle, E. Ferraris, A. Lasagna, G. Rizzo, E. Bonzano, M. Paulli, M. Lucioni *Unit of Anatomic Pathology, Department of Molecular Medicine, Fondazione IRCCS Policlinico San Matteo, University of Pavia, Italy Background & objectives: Breast carcinoma with apocrine differentiation is a rare (1%) breast cancer histotype characterized by apocrine morphology in >90% of cells, that typically shows positivity for androgen receptor (AR) and it’s either triple-negative or HER2-positive, non luminal. Methods: At our Institution, 37 patients were diagnosed with breast carcinoma with apocrine differentiation between January 2010 and December 2020. Data about patient’s age, and tumour histological grade, ER, PR, Ki-67, AR and HER2 status and TNM staging was obtained from pathological report. Of note, no patient had undergone neoadjuvant therapy. Results: Of our 37 cases, 25 were classified as high grade, and 11 as low or intermediate grade according to the Nottingham His- tologic Score. The high grade group comprised slightly younger patients (median age: 69 vs 71,5) and showed a statistically sig- nificant prevalence of HER2-amplified tumours (14/25 vs 1/12, p=0.0106) and a higher Ki-67 average score (28% vs 13% in the low and intermediate grade tumours); no difference was observed in loco-regional stage of the tumour (average primary tumour dimension: 22,7 mm vs 18,1 mm; cases with positive lymph nodes: 11/25 vs 6/12). Conclusion: Despite being regarded as an histotype with a more indolent course, our data shows that even lower grade apocrine car- cinoma has a high propensity for loco-regional spread, and should be managed accordingly; the net difference in prevalence of HER2 amplification between low and high grade tumours suggests that different, unknown molecular events underlie disease progression in the two groups, and warrants further studies to define the biol- ogy of this histotype. OFP-10-014 Claudin-1 expression in triple-negative breast cancers (TNBCs) and its clinical significance A. Ouban* *Alfaisal University College of Med, Saudi Arabia Background & objectives: TNBC is an aggressive disease, lacking therapeutic and prognostic markers. Claudin-1, a biomarker with a prognostic value in several tumours, reportedly has conflicting results in TNBCs. The authors shed some light on claudin-1 expres- sion in TNBC and its value. Methods: We analysed the expression of claudin-1, a tight-junction protein that has a promising prognostic value in several cancers, by immunohistochemistry, in TNBC cases from the King Khaled university hospital. This expression was cross-checked against clinical-pathological criteria of TNBC patients, and against beta- Catenin expression in the same patients’ sample. Results: Claudin-1 was significantly expressed in the majority of TNBC cases. This expression was significantly correlated with lymph node metastases, tumour invasion, higher tumour nuclear grade, higher clinical and TNM staging, adverse survival outcome and failure to achieve remission following neoadjuvant chemotherapy (NAC). TNBCs’ claudin-1 expression was also correlated with grade-2 abnormal expression of beta-Catenin (AEB) in the same patients’ sample. Conclusion: Most cases of TNBCs in our institution expressed the claudin-1. This expression is strongly linked to parameters of poor prognosis. The above may shed some light on the possible role of claudin-1 in TNBC; and may present an opportunity for the use of this biomarker in the management of TNBC patients. OFP-10-015 Filamin-A expression in triple negative breast cancer (TNBC) and its clinical significance A. Ouban* *Alfaisal University College of Med, Saudi Arabia Background & objectives: TNBC presents a clinical dilemma with early recurrence, metastases and poor survival outcome. Filamin-A is recently discovered protein which plays a dual role as oncogene and tumour-suppressor gene in many cancers. This study analyzes the expression of Filamin-A in TNBCs. Methods: This study analysed the expression of Filamin-A, using immunohistochemistry, in a tissue microarray of 50 cases of triple-negative, invasive ductal breast carcinomas. Filamin-A expression was cross-checked against clinic-pathological attributes of the TNBC cases including age, grade, clinical stage and TNM staging. Filamin-A expression within the cell was analysed. The TNBC cases were further categorized by the intensity of Filamin- A expression. Results: A significant majority of this study’s TNBCs exhibited positive expression of Filamin-A. All Filamin-A positive TNBC cases expressed the protein in the cytoplasm of the tumour cells. Filamin-A expression was significantly correlated with TNBC grade, clinical stage, and TNM staging. A significant majority of TNBC cases had the highest intensity of Filamin-A expression (35/45, IRS=12). This study is the first to analyse expression of Filamin-A only in TNBC cases. When compared with other studies which analysed this expression in breast cancer sets (mixed sets); it was noted that the number of Filamin-A positive cases were much higher in this study’s TNBC set. Conclusion: Given the versatile role of Filamin-A, with its numer- ous interactions with cytoskeleton components of tumour cells and with signalling proteins, in addition to its role in modulating sen- sitivity to the chemotherapeutic agent Docetaxel, make the results of this study particularly important in TNBC patients, who have few management options. This study provides evidence of the clini- cal significance of Filamin-A in TNBCs, and proposes additional studies to pinpoint the exact function of this protein in this subset of breast cancer patients. OFP-10-016 Nullisomy of chromosome 17 in invasive breast cancer: charac- terisation of a rare and puzzling genomic event S43