ECP 2023 Abstracts

S153 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Conclusion: The management and prognosis ACC of breast, remains uncertain and novel grading systems and immunohistochemical mark- ers do not improve accuracy in aggressive cases detection. Tumour size over 5 cm seems to be the best prognostic factor in our series. E-PS-02-004 Upgrading of high-risk breast lesions in patients with multiple biopsies: is surgery essential? N. Arı*, S.E. Horoz, K. Kolçak, H. Kaya *Marmara University School of Medicine, Department of Pathology, Turkey Background & objectives: High risk breast lesions are associated with increased risk of malignancy. Upgrading of these lesions to higher grade lesions is commonly encountered in subsequent biopsies. In this study, upgrading status of these lesions is investigated in patients with multiple biopsies. Methods: Biopsy reports with initial diagnosis of high-risk breast lesions (atypical ductal hyperplasia (ADH), atypical lobular hyperpla- sia (ALH), lobular carcinoma in-situ (LCIS), intraductal papilloma and sclerosing adenosis) between the years of 2018-2022 were retrieved from the hospital records. Among these patients, 40 patients who underwent more than one biopsy (either multiple core needle biopsies or subsequent surgical excision) were included. Results: Core needle biopsy results of 40 patients were compared with their subsequent (mainly excisional) biopsies. Upgrading to a higher- grade lesion was seen in 45% (n=18) of the patients. 43,7% (n=14) of the patients who were initially diagnosed as intraductal papilloma (n=32) were found to have a higher-grade lesion in subsequent biopsies, 9,3% (n=3) of them diagnosed as carcinoma and 21,8% (n=7) of them as DCIS. All patients who were initially diagnosed as ALH (n=2) dis- played upgrading in their excision specimens. 2 of 3 patients with ADH were upgraded to DCIS whereas no patients with sclerosing adenosis were observed to have an upgraded lesion in subsequent biopsies. Conclusion: Management of high-risk breast lesions remains as a matter of debate since both surgical excision and patient follow-up constitute the options. Overtreatment with unnecessary surgical inter- ventions should be avoided. However, inadequate sampling with core needle biopsy is a major concern for underdiagnosis of high-grade lesions, especially if radiological-pathological correlation cannot be accomplished. In this study, high upgrade rates in subsequent biopsies highlight the possibility of underdiagnosis of high-risk lesions, includ- ing carcinoma, if excisional biopsy is not performed. E-PS-02-005 Synchronous bilateral breast carcinoma and axillary non-Hodgkin lymphoma: two case reports and literature review R. Ayadi*, E. Braham, H. Ichrak, F. Loued, O. Ismail, A. Ayadi *Hôpital Abderrahmane Mami, Tunisia Background & objectives: Breast cancer is the most prevalent tumour for women worldwide. Synchronous breast carcinoma and lymphoma are rare. It is of high rate of misdiagnosis in clinical practice. The aim is to describe a clinicopathological data of patients with both diagnoses. Methods: We report two patients who developed simultaneous breast lymphoma and breast carcinoma aged 74 and 85 years. Results: Two women presented with a palpable mass in the left breast and a right axillary adenopathy. A CT of the chest showed multiple right axil- lary nodes and mass in the left breast. They underwent excisional biopsy of a right axillary node which demonstrated diffuse large B-cell lymphoma. IHC showed CD3(–), CD20(+), CD10(–), BCL-6(–), MUM-1(strong+) and CK(–).Ultrasound-guided needle core biopsy of the breast lesions showed infiltrating ductal carcinoma in the left breast, and oestrogen and progesterone receptor (+), HER2 receptor (-).Thoracic CT scan, ultrasound scan of abdominal, pelvic and superficial lymph nodes and bone marrow were performed. No metastasis was found. They received R-CHOP to cover the breast cancer and lymphoma. Conclusion: These two patients remind us of the coexistence of breast can- cer and breast lymphoma. The diagnosis of synchronous malignancies poses challenges for both the diagnosing pathologist and the treating clinician. E-PS-02-006 Pathologic characteristics and response of invasive lobular carci- noma of the breast after neoadjuvant chemotherapy J. Azevedo*, M. Alzamora, A. Coutada, A. Lapa, L. Gonçalves, N. Coimbra, C. Leal *Pathology Department, IPO-Porto, Portugal Background& objectives: Invasive lobular carcinoma (ILC) is considered a distinct clinical and biological type of breast cancer, being less responsive to neoadjuvant chemotherapy (NAC) compared to ductal invasive carci- noma. We aim to characterize our population with ILC that received NAC. Methods: Retrospective analysis of all patients diagnosed with ILC treated with NAC followed with surgery in our institution between 2011 and 2021. We evaluated clinical and pathologic features including age, surgery type, histological grade and immunohistochemical profile on biopsy, tumour size with magnetic resonance, before and after NAC, and pathological response. Time of follow-up, recurrence, metastasis and overall survival were recorded. Results: 115 cases were included, the majority presenting in biopsy with G1/G2 tumours (n=95, 90.87%). Most cases were positive for hor- mone receptors (HR) and HER2 negative (n=96, 83.5%) with smaller subgroups HR-/HER2+ (n=5, 4.3%), HR+/HER2+ (n=11, 9.6%) and triple negative (n=3, 2.6%). Complete pathological response (pCR) was achieved in 4 (3.5%) cases; all pleomorphic and HER2+ (3 were HR-). All these patients are disease-free. In cases with partial pathological response (n=111, 96.5%), median of tumour size before and after NAC was 3.6cm [0.6-11cm] and 4cm [0.2-12cm], respectively. Additionally, in 13 of pathology partial responders small foci (<0,1cm) with low cellularity were observed throughout the tumour bed. Conclusion: The vast majority of ILC are low-grade with low prolif- erative index, oestrogen receptor-positive with poor response to NAC. The few cases of pCR were associated with HER2 positivity, indicating that this relative resistance to NAC may be more related to molecular characteristics than histologic subtype. We believe that assessment of partial response by AJCC ypT can be affected by interobserver hetero- geneity, as evaluation of the largest contiguous focus can be difficult due to scattered foci over the tumour bed. E-PS-02-007 Incidence and clinicopathologic features of human epidermal growth factor receptor 2 (HER2)-low breast cancer Y.K. Bae*, M.C. Kim *Department of Pathology, Yeungnam University College of Medicine, Daegu, Republic of Korea Background & objectives: HER2-low breast cancer (BC), which is defined as immunohistochemistry (IHC) 1+ or 2+ without gene ampli- fication, is a recently proposed HER2 category for new HER2-targeting drugs. We investigated the incidence, clinicopathologic characteristics, and prognosis by comparing HER2-negative and HER2-positive BCs. Methods: We obtained clinicopathologic information [age at diagnosis, tumour size, histologic type, histologic grade, lymphovascular invasion, lymph node status, IHC results for oestrogen receptor (ER), progesterone receptor (PR), HER2, and Ki-67, and clinical outcomes] from 2,309 patients with primary invasive BC who underwent curative surgery at Yeungnam University Hospital between November 2007 and December 2014. Results: Of the 2309 cases, 1497 (64.8%) were HER2-negative, 348 (15.1%) were HER2-low, and 464 (20.1%) were HER2-positive. Com- pared with HER2-negative BCs, HER2-low BCs were associated with