ECP 2023 Abstracts

S163 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 and hormone receptor-positive Her2-positive subtypes of the primary tumour (PT). Methods: Surgical specimens of the PT and local metastases of 36 patients with breast cancer were studied. Immunohistochemistry (ER, PR, Her2/neu, Ki67) and SISH (HER2 gene) were used to assign the tumour to one of the surrogate biological subtypes. The frequencies of subtype changes of regional metastasis compared with PT were evalu- ated and then compared using Fisher exact probability test. Results: Subtypes of PT and metastasis were concordant in 29 cases (80.6%, 95% CI 63.4-91.2%), discordance of the subtypes was observed in 7 cases (19.4%, 95% CI 8.8-36.6%) (p<0.05). Among 20 cases with a triple negative subtype of PT, in 1 case metastasis had another (luminal B) subtype (5%, 95% CI 0.3-26.9%). Of the 9 cases with hormone receptor-negative Her2-positive subtype of PT, in 4 cases metastasis had other (2 triple negative, 1 luminal A, 1 Luminal B) subtypes (44.4%, 59% CI 15.3-77.3%). Among 7 cases with hormone receptor-positive Her2-positive subtype of PT, in 2 cases metastasis had other (1 luminal A, 1 luminal B) subtypes (28.6%, 95% CI 5.1-69.7%). Conclusion: The biological subtype of breast cancer with regional metas- tasis in most cases remains stable among the cases of the entire sample. Discordance of the subtype is most often observed in cases with a hor- mone receptor-negative Her2-positive subtype of the primary tumour. E-PS-02-041 Evaluation of tonsil as tissue control for immunohistochemical demonstration of oestrogen receptor H.L. Kristoffersen*, R. Røge, S. Nielsen *NordiQC, Aalborg Universityhospital, Denmark Background & objectives: The purpose of this feasibility-study was to evaluate the applicability of normal tonsillar tissue as positive tis- sue control in immunohistochemical staining for Oestrogen Receptor (ER). This was accomplished by comparing the analytical sensitivity in validated and selected suboptimal staining protocols. Methods: Ten tonsils and eleven breast carcinomas (BC) with vary- ing ER intensity were included. In addition to the validated reference immunohistochemical protocol, materials were stained using modified protocols with both reduced analytical sensitivity and with increased analytical sensitivity. The ER expression was quantified using H-scores, and for diagnostic evaluation a cut-off at ≥10% positive neoplastic cells was used in the BCs. Results: Using the validated reference protocol, 8/11 BCs were ER positive with a mean H-score of 81 whereas tonsillar germinal centre lymphocytes and squamous epithelial cells showed a mean H-score of 6 and 56, respec- tively. The protocol with increased analytical sensitivity also characterized 8/11 BCs as ER positive, mean H-score 130 and H-score of 16 and 103 in tonsillar lymphocytes and epithelial cells, respectively. The protocol with most reduced analytical sensitivity characterized 6/11 BCs as positive, mean H-score of 31 while tonsillar germinal centre lymphocytes and epithelial cells showed H-scores of 2 and 21. Conclusion: Tonsil was found applicable as critical positive tissue control for immunohistochemical demonstration of ER including low level ER expressing BCs. Protocols providing reduced levels of H-score in germinal centre lymphocytes and epithelial cells was associated with false negative BCs. Increased analytical sensitivity and associated increased H-scores in tonsil did not induce false positive BCs. More studies with increased number of BCs must be performed to validate the observation and potentially combined with image analysis to elucidate H-score read-out consistency. The project was supported by The Biomedical Laboratory Scientist Education and Research Fund in Denmark. E-PS-02-042 Clinicopathological features of male breast cancer: a single institu- tion experience H. Lee*, O. Lee, S. Son, C.G. Woo *Chungbuk National University, Republic of Korea Background & objectives: Male breast cancer (MBC) is a rare malig- nancy while female breast cancer is one of the most common malignan- cies in Korea. Clinical and pathological characteristics of MBCs were investigated and described. Methods: Patients of MBC were collected who visited Chungbuk National University from January 2011 to December 2022. Pathologic data were obtained including TNM stage, presence of ductal carcinoma in situ, lymphovascular or perineural invasion. Immunohistochemistry (IHC) results such as oestrogen and progesterone receptors, HER2, p53, and ki-67 index were assessed. Results: The average age of patients was 64.5 years (range 41-89). Ten out of 13 patients underwent mastectomy, including one with distant metastasis at the time of surgery. Lymph node metastasis was found in four out of 9 who underwent axillary lymph node assessment. IHC showed that every case was positive for hormone receptors and nega- tive for HER2. When ki-67 index was set at 14%, five (38.5%) and 8 (61.5%) were classified as luminal A- and B-like, respectively. No TP53 gene mutation was found according to p53 IHC pattern. Clinical follow-up data revealed that three (33.3%) out of 9 who had underwent curative mastectomy had recurrence and/or distant metastasis. Conclusion: MBCs occur in elderly men and almost all have luminal A- or B- subtypes. Therefore, if an MBC showed HER-positive or triple-negative type by IHC, further studies were probably required including radiologic and genetic assessments. E-PS-02-043 Clinicopathological characteristics and prognostic analysis of fibrotic focus in HER2-negative breast cancer Y. Liu*, M. Yue, S. Wu *The Fourth Hospital of Hebei Medical University, China Background & objectives: The aim of this study is to assess the fibrotic focus (FF) with clinicopathological features and prognosis in patients with HER2-negative breast cancer, especially with HER2-low breast cancer. Methods: We retrospectively reviewed the data of 293 patients with HER2-negative, stage I-II, invasive breast cancer of non-specific types from September 2017 to December 2018. The clinicopathological data of the patients were collected and followed up. The FF with clinico- pathological features and prognosis in patients with HER2-low and with HER2 0 breast cancer was analysed. Results: The study cohort included 178 cases (60.8%) with HER2 low and 115 cases (39.2%) with HER2 0. FF were correlated with older age, intermediate and low NHG, vascular invasion, HR positivity, HER2 low status, high Ki67 expression and low TILs. Univariate sur- vival analysis showed that FF was significantly associated with shorter progression-free survival (PFS). Stratified analysis indicated that DFS was longer in patients without FF compared to those with FF in the HR- negative (HR=0.313, p=0.012) and HER2 low (HR=0.272, p=0.043) groups. DFS was also significantly longer in patients without FF com- pared to those with FF in the HR-positive (HR=0.069, p=0.002) and HER2 0 groups (HR=0.129, p<0.001). Conclusion: The results indicated that patients with FF exhibited distinct biological characteristics and prognostic significance, par- ticularly in the HR-negative and HER2 0 groups. To our knowledge, this was the first study to report this finding. This provides a ration- ale for accurate diagnosis and treatment of HER2-negative breast cancer. E-PS-02-044 Tumour mutation burden and infiltrating immune cell subtypes influenced the breast cancer prognosis Y. Liu*, J. Li, H. Liu