ECP 2023 Abstracts

S162 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Results: Partial CAIX expression was found in 56.2% of BC cases with heterogenous HER2-expression. The pattern of expression was dynami- cally alternating with CAIX+ areas becoming virtually HER2-negative. Highest HER2-positivity was seen in the proximity of CD31+ microves- sels. Gradual Her2-loss could be observed from a mean vessel distance of 85.08±15.37 μm (range 42.75 – 157.31 μm) turning in a complete HER2- negative and CAIX-positive phenotype. The transition zone appeared as double HER2+/CAIX+. CD31+ vessel-to-vessel distance was significantly higher in CAIX+ samples (mean values 80.2±22.6 vs 311.4±77.0). High intensity CAIX+ zones surrounded foci of ischemic necrosis in 4/60 cases. Conclusion: HER2-low status is becoming important for targeted HER2-therapy. We demonstrate that intratumoral target distribution is related to tissue perfusion and adapation to hypoxia. The upregulation of CAIX highlights hypoxic tumour regions also featured by dynamic loss of HER2. The relation to the microvessel network could also be clearly established. The occurrence of CAIX indicates to a clinically significant resistance mechanism interfering with the specific effect of new-genera- tion HER2 based therapies. E-PS-02-037 Not all breast adenoid cystic carcinomas are created equal M. Khmou* *National Institute of Oncology, Morocco Background & objectives: Breast adenoid cystic carcinoma (AdCC) is a rare salivary gland-like tumour. The solid-basaloid AdCC is rare subtype (less than 100 published cases). In opposition to classic AdCC, the solid-basaloid subtype has an aggressive clinical course, with local recurrences and metastases. Methods: We report the case of a 78-year-old woman with a right breast mass, evolving for 2 months. Examination revealed a painless mass in the upper outer quadrant. No axillary lymphadenopathy was detected. Mammogram and ultrasound revealed a 2 cm spiculated mass with scattered microcalcifications. The lesion was excised after a nega- tive biopsy, by lumpectomy with sentinel node dissection. Results: Microscopically, the tumour was exclusively composed of solid nests of basaloid cells with infiltrative margins. Trabecular, tubular, or cribriform patterns were not identified. The tumour cells had a medium to large size and displayed a high nuclear to cytoplasmic ratio with scanty cytoplasm and large, round to oval nuclei. The intervening stroma was densely hyalinized. The typical biphasic pattern of myoepithelial-ductal differentiation as seen in the classic AdCC was not seen in this case. Immunohistochemistry showed diffuse positivity for CD117, SOX10 and CK7 in all neoplastic cells. They lacked oestrogen receptor, proges- terone receptor, human epidermal growth factor receptor-2 expression. They were also negative for Synaptophysin, chromogranin, GCDFP15 and Mammaglobin. Conclusion: The aim of this report is to describe and to draw attention to this rare and aggressive variant of AdCC, characterized by a higher incidence of distant metastases compared with the classic AdCC. Mor- phological differential diagnosis of this entity is often challenging, it include solid ductal carcinoma in situ, solid papillary carcinoma, neu- roendocrine tumours and invasive breast carcinoma of no special type. While minimal standardized data on therapeutic management is avail- able, large-scale studies with long-term follow-up for patients are necessary. E-PS-02-038 Unexpected finding in a long lasting sclerosed fibroadenoma - mul- tiple foci of high grade invasive ductal carcinoma: a case report A. Klevišar Ivančič*, R. Eržen Jakšič, R. Petrič, G. Gasljevic *Institute of oncology, Slovenia Background & objectives: Breast carcinoma (BC) arising in fibroad- enoma (FA) is extremely rare; it occurs in < 0.1 % of FA specimens. High-quality ultrasonosonography (US) has a high negative predictive value. However, in the presence of suspicious US findings, histopatho- logical correlation is mandatory. Methods: A 53-year-old woman presented with 20-years lasting tumour, increasing in size, previously diagnosed as FA on US. Family history was BC-negative. Mammographically, it was 7cm large, well- defined. US showed small foci suggestive of necrosis. Axillary lymph nodes were unsuspicious. Two core needle biopsies showed only abun- dant hypocellular hyalinized stroma. Because of the tumour size and radiological-pathological discrepancy, tumourectomy was performed. Results: Macroscopically, the excised tumour was well-defined, elastic. It weighted 95 g, measured 7x6x4 cm, was focally surrounded by a small amount of breast parenchyma. On cut surface, it was pale white with focal small softer areas. Histology showed multiple foci (at least 30) of high-grade invasive ductal carcinoma (IDC) measuring from 1-20 mm and ductal carcinoma in situ scattered within sclerosed FA. They represented approximately 70% of FA volume, mainly being lim- ited to FA (two of them minimally infiltrated breast parenchyma). Sur- gical margins were tumour-free. IDC was ER/PR positive and HER-2 negative. Later on, a sentinel node was excised being negative. Patient is currently waiting for decision about further treatment. Conclusion: In conclusion, we describe a very rare case of invasive BC arising in long lasting FA. Although clinically unsuspicious, therapeutic decision was guided by FA-size and radiologic-pathologic discrepancy. Excision of FA with histopathological examination should be performed in any of the following clinical scenario: increase in size during US fol- low-up, presence of suspicious findings on US examination, immobile and poorly circumscribed lesion, advanced age (> 35 years), a family history of cancer and FA greater than 2.5 cm in diameter. E-PS-02-039 Study of CD 163 expression in breast cancer tissue O. Kolomiiets*, R. Moskalenko *Department of Pathology Sumy State University, Ukraine Background & objectives: Macrophages are one leading the repre- sentatives of the tumour microenvironment is crucial in developing metastasis, prognosis, recurrence of breast cancer (BCa). The aim. To investigate the expression of CD 163 receptors in the tissue of BCa with and without calcifications. Methods: In the work, 60 BCa tissue samples were studied and divided into two groups. The first group included tissues of breast BCa with calcifications (30 samples), and the second group - BCa tissue without microcalcifications (30 samples). The work used an immunohistochem- ical study (IHC) of CD 163 expression and statistical processing of the results (Student’s test). Results: When examining a group of BCa tissue samples with calcifi- cations, it was established that the average value of CD 163 expression was 53.21 ± 3.05. In the control group of BCa tissue without calcifica- tion, CD 163 expression was 65.57 ± 3.75 (р˂0.05). Conclusion: Our study shows that the expression of CD 163 receptors is higher in the tissue of BCa without calcifications compared to the tumour tissue samples of the first group. These results may indicate different mechanisms of metastasis development in the tumour tissue of BCa in the presence of calcifications. E-PS-02-040 Heterogeneity of Her2-positive and triple negative breast cancer subtypes in primary tumour and local metastasis K. Konyshev*, S. Sazonov *Institute of medical cell technologies, Ural state medical university, Russia Background & objectives: The aim of the study was to assess the sta- bility of the biological subtype of breast cancer in regional metastasis in cases with triple negative, hormone receptor-negative Her2-positive