ECP 2023 Abstracts

S154 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 lymphovascular invasion, ER positivity, and PR positivity. Furthermore, HER2-low BCs had a smaller tumour size, lower histologic grade, positive ER and PR status, and low Ki-67 status than HER2-positive BCs. When we stratified the patients based on ER status, there was no difference in overall survival (OS) and disease-free survival (DFS) between the HER2- negative and HER2-lowBC groups. However, patients with HER2-lowBC had better DFS in ER-positive group and worse OS in ER-negative group than those with HER2-positive BC. Conclusion: The incidence of HER2-low BCs was lower than expected. They showed higher ER and PR expression than HER2- negative and HER2-positive BCs. There was no survival difference between HER2-low and HER2-negative BC patients regardless of ER status. However, prognosis between HER2-low and HER2-positive BCs depended on ER status. ER status needs to be considered in the therapeutic strategies for the treatment of patients with HER2-low BC. E-PS-02-008 Two rare cases of adenosis tumour (nodular adenosis) R. Balan*, I.D. Căruntu, R. Socolov, I. Păvăleanu, L. Toma, L. Lozne- anu, A. Grigora ș , T.A. Balan, C. Amalinei *"Grigore T. Popa" University of Med, Romania Background & objectives: Adenosis tumour or nodular adenosis (NA) represents a rare entity, in which a benign lobulocentric proliferation of glands compressed by fibrosis, called sclerosing adenosis forms a firm, homogenous, nodular mass. Sometimes clinical and histopathological aspects of NA can mimic carcinoma. Methods: We report two cases of NA, in two patients, aged 18 and 41 years, respectively, admitted in the Clinical Hospital of Obstetrics and Gynaecology „Elena Doamna” from Iasi, Romania. In both cases lumpec- tomy was performed. The specimens were referred to Pathology Service and histopathologically examined by routine staining (H&E) and immu- nohistochemical techniques (SMA, p63, CK5/6) to exclude a carcinoma. Results: The clinical and ultrasound examination revealed a solid hypoechogenic nodule in both cases, one with central areas of liquefac- tion. Macroscopically, one case presented a multinodular aspect, with microcystic areas, while the other was a less circumscribed nodular mass. The histopathological diagnosis revealed a well circumscribed nodular proliferation of slightly dilated glandular structures, with predominantly tubular pattern, slightly lined by simple epithelium, with partial preservation of myoepithelial cells, surrounded by collagenous stroma. The other case revealed nodular areas with sclerosing adenosis and florid tubular prolif- eration, with different growth patterns. The presence of myoepithelial cells was confirmed through immunohistochemical evaluation of p63, SMA, and CK5/6, all markers presenting diffuse positive expression. Conclusion: Adenosis tumour is a rare entity, which is characterized by a variety of growth patterns, aspects that, along with clinical and imaging characteristics, differentiate NA from other benign entities or carcinomas. The two presented cases, which are notable for the extreme ages of the patients, as well as for the heterogeneous morphological aspects, sometimes requiring immunohistochemical confirmation, provide additional data that can complete the clinical-pathological picture of nodular adenosis. E-PS-02-009 Vein invasion in breast cancer – a single centre experience A. Baltan*, S. Costache, A. Gont, A. Chefani, C. D’Arrigo *Poundbury Cancer Institute, Romania Background & objectives: There is wide recognition of vein invasion in certain tumours (colorectal, pancreatic, or renal). This has not been adequately distinguished from lymphatic invasion in breast cancer. Nevertheless, vein invasion appears to be a distinct event of uncertain clinical significance. Methods: We have routinely screened and reported the presence of vein invasion in breast carcinoma in our practice. All positive or suspicious cases on morphological grounds are confirmed with IHC for desmin. To establish prevalence, we reviewed 173 surgical excisions (screening and symptomatic patients) from a single institution between June 2022 and March 2023. Results: A total of 16 cases with vein invasion were identified (9.24% of all cases). These were mostly present in elderly women (>80 years old), in higher-grade carcinoma and higher tumour burden (size> 20mm). We have observed vein invasion within the primary tumour bed, in perinodal tissue, or in both. Out of the 16 cases, 11 had vein invasion only at the primary site, 3 within the perinodal tissues only and 3 in both sites. In addition, there was no significant association with lymphatic invasion. Conclusion: Vein invasion is underrecognized in breast cancer. Desmin greatly facilitates its identification since in breast tissue it stains only blood vessels. Lack of correlation with lymphatic invasion points towards these being distinct events of tumour progression. Vein invasion at other tumour sites is associated with worse prognosis and higher rates of systemic metastases. In breast cancer, anecdotal associa- tion with brain metastases warrants further studies to assess potential link with systemic disease. E-PS-02-010 Simultaneous presentation of a giant malignant phyllodes tumour of the breast and high-grade renal cell carcinoma – a rare presen- tation: a case report Y. Belogrivtseva*, A. Israh, A. Arriola, M. Mollaee *Temple University Hospital, USA Background & objectives: Phyllodes tumours (PTs) are rare, account- ing for less than 1% of breast tumours. It is classified into benign, borderline, and malignant based on cellularity, stromal overgrowth, stromal cell atypia, infiltrative borders, and the presence of heterolo- gous component(s). Methods: We report a case of a 59-year-old female, presenting with a rapidly enlarging 31 cm mass of the right breast with focal skin ulcera- tion and purulent discharge. Results: Follow-up imaging studies for staging revealed mediasti- nal adenopathy, and an incidental 9.7 cm exophytic renal mass along with bilateral enlarged inguinal lymph nodes. The patient underwent a mastectomy and subsequent partial nephrectomy within a few weeks apart. Histopathologic examination of the breast mass biopsy showed a fibroepithelial tumour and a phyllodes tumour was favoured. Sub- sequent mastectomy specimen revealed malignant phyllodes tumour with marked necrosis and positive margins. A partial nephrectomy performed for the renal tumour showed a high-grade papillary renal cell carcinoma with perinephric extension and three positive lymph nodes. Conclusion: The genomic landscape of PT from sequencing could provide more insight into its molecular pathogenesis, help improve diagnostic accuracy, and identify potential drug targets for malignant PT, however, there are limited published studies with this informa- tion. Reporting the simultaneous presentation of these two high-grade tumours would help to better our understanding of potential molecular associations driving these two distinct high-grade processes. E-PS-02-011 Interobserver agreement between pathologists assessing tumour- infiltrating lymphocytes in breast cancer by applying International TILs Working Group recommendations E. Benammou*, D. Bacha, I. Mallek, S. Gharbi, M. Hajri, H. Mestiri, A. Lahmar, S. Ben Slama *Department of Pathology, Armand Trousseau Hospital-Sorbonne University, France Background & objectives: Several studies highlighted the prognos- tic and predictive values of tumour-infiltrating lymphocytes (TILs) in