ECP 2023 Abstracts

S157 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Conclusion: Reported to be the 0.5% of all invasive breast carcinomas, which was consistent with the incidence we found in our series, IPC is a rare type of carcinoma. The immunophenotype was similar in all our cases except for Progesterone and Ki67, which showed high variability. Only one of the cases had lymph-node metastasis in a single lymph- node out of 30 examined, although further studies are mandatory for a better understanding of the prognosis of this histotype. E-PS-02-018 The prognostic and predictive values of androgen receptor expression in breast cancer patients who undergone neoadjuvant chemotherapy M.Y. Çelik*, A. Umit, H.E. Pestereli, A.M. Tatlı *Akdeniz University Department of Pathology, Turkey Background & objectives: The aim of this study is to determine the prevalence of androgen receptor (AR) expression status in breast cancer patients who undergo neoadjuvant chemotherapy, including all molecu- lar subtypes of breast cancer, and to investigate its relationship with known prognostic factors. Methods: Neoadjuvant chemotherapy (NACT) given 176 patients with luminal A (n:12), luminal B HER2 negative (n:57), luminal B HER2 positive (n:49), HER 2 positive (non-luminal) (n:25) and triple nega- tive breast carcinoma (n:33) diagnosed at Akdeniz University Hospital were included. Histopathological parameters, NACT response and AR expression status were documented. AR expression was detected by immunohistochemically, using antibody clone AR 441. Results: In the pre-NACT biopsies, 104 cases were AR(-) (59,1%) and 72 cases were AR(+) (40,9 %). The number cases with pathological complete response after NACT were 74 (42%). There was no statistically significant difference between the pre-NACT AR status and pathological complete response(p=0.480). When we compared the pre-NACT and post-NACT cases, there were statistically significant difference in oestrogen receptor (p=0,001), and Ki67 proliferation index (p=<0,001). In between pre-NACT AR(-) and AR(+) cases, we observed statistically significant differences in tumour size (p=0,024), histological grade (p=0,022).The mean Ki67 score of the pre-NACT AR-negative group was 50%, while the mean Ki67 score of the AR-positive group was 40% (p=0.004). Conclusion: Although there was no statistically significant relationship between AR expression and clinicopathological parameters and sur- vival in breast carcinoma cases with neoadjuvant chemotherapy in our study, to get more detailed information, multicentred larger series with longer observation are needed in future studies. Furthermore, given the current knowledge and literature, the relevance of AR expression in relation to clinical and pathological parameters is particularly promis- ing in terms of new therapies to be developed. E-PS-02-019 Axillary nodal involvement of post-radiation angiosarcoma of the breast: case report and discussion A. Cernat-Stefan*, D. Raduta, T.G. Jaswal, A. Ro ș ulescu, T. Georgescu *Colentina University Hospital, Romania Background & objectives: Post-irradiation mammary angiosarcoma (PIMA) is a high-grade vascular proliferation that develops in patients who received radiotherapy for a prior epithelial tumour of the breast. Axillary nodal involvement is exceptionally rare, with only few isolated case reports in the scientific literature. Methods: We reviewed the case of a 67 years old female patient who presented with skin lesions and breast tumours. A history of invasive ductal carcinoma is noted. In December 2022 the patient underwent a breast biopsy, and in February 2023 a left mastectomy with lym- phadenopathy was performed. All Hematoxylin and Eosin (H&E) and immunohistochemical (IHC) stained slides were reviewed. Results: The patient had a prior history of lumpectomy with lym- phadenopathy for invasive ductal carcinoma in 2007 and received polychemotherapy, hormonal therapy, and radiation. Mammography showed thickening of the left breast tegument in all quadrants and the presence of multiple nodules and an intensely opaque left axillary lymph node. IHC performed on the breast biopsy showed positivity for CD31, confirming the diagnosis of vascular proliferation. In the lymphadenectomy specimen, a nodular structure with an appearance of atypical vascular proliferation was identified, which presented lym- phoid tissue in the periphery, suggestive of nodal metastasis. IHC for ERG, MYC, FLI1, CD31 and D2-40 was performed, confirming the diagnosis of PIMA with nodal involvement. Conclusion: The particularity of the case resides in the presence of PIMA nodal metastasis. The differential diagnosis, in this case, is that of an atypical vascular lesion, also secondary to irradiation. Strong intralesional expression of MYC and peripherally located lymphatic tissue points to lymph node metastasis. However, nodal involvement is a rare event in the natural history of angiosarcomas and is not a firm indication of lymphadenectomy at this time. E-PS-02-020 Diagnostic shift in triple negative breast cancer originating from detailed subtyping and definition of receptor status - a retrospec- tive analysis L. Christe*, E. Werner Rönnerman, A. Kovács, B. Linderholm, A. Valachis, T. Rau *Institute for Tissue Medicine and Pathology, University Bern, Switzerland Background & objectives: TNBC is a heterogenous group of tumours. Novel breast cancer subtypes as well as the thresholds for receptor status impact the definition of TNBC directly. In a retrospective cohort, the extent of this diagnostic shift was assessed quantitatively. Methods: A previously published cohort of 366 patients diagnosed with TNBC between 2007 and 2015 and predominantly no neoadjuvant treatment was reclassified according to the WHO 2019 classification using morphology, a panel of immunohistochemistry and Her2-CISH. Tumours were evaluated for stromal tumour infiltrating lymphocytes (sTILs), tumour budding and survival analysis. Diagnostic consensus was achieved between four experienced pathologists. Results: According to receptor status, 55 carcinomas (15.0%) were re-classified as ER positive (53) or even Her2 positive (2). Subtyping according to the current WHO classification revealed 56 apocrine carci- noma (15.3%), 9 lobular (2.5%) and 17 rare special types (4.6%). Proto- typical TNBC of no special type remained in only 221 cases (60.4%). In multivariate analysis higher grading and advanced nodal status showed the expected worse prognosis. Regarding subtyping, apocrine like lobular carcinomas showed significantly better outcomes in comparison to NST subtypes, whereas rare special subtypes consisting mainly of metaplastic carcinomas appeared as unfavourable. sTILs and tumour budding dem- onstrated the expected outcome but did not reach statistical significance. Conclusion: A tremendous morphology-driven diagnostic shift in TNBC was introduced with the current WHO-classification. Differences in ER assessment and the subtype of apocrine carcinoma contribute the most to this effect. The survival analysis underpins the different biologi- cal behaviour in the distinct subtypes. Interpretation and conceptualiza- tion of clinical trials and digital pathology algorithms should encounter diagnostic shift as a substantial phenomenon. Documentation according to SPIRITpath guidelines and access to digital image repositories might prepare for future adaptations with upcoming classifications. E-PS-02-021 Outline of the implementation of a national consensus regarding the translation from guidelines to clinical practice evaluation of the Breast Cancer Biomarker HER2 N. Coimbra*, F. Schmitt, J. Magalhães, M.J. Brito, P. Borralho, S. André, R. Celestino, F. Duarte-Ramos