ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Conclusion: -SLN involvement is very low in our series of EPC (5.5%). -The frequences of EPC without infiltration and invasive carcinoma are 0% and 11%, respectively. -The presence of invasive carcinoma is only confirmed in the surgi- cal specimen. -Therefore, we suggest assessing the indication for SLN in those cases where invasive carcinoma is confirmed. PS-01-006 Applicability of One Step Nucleic Acid in cytokeratin 19 nega- tive tumours, based on a series of cases A. Córdoba*, M. Bronte, I. Fernandez, I. Amat, R. Beloqui, A. Larrea *Complejo Hospitalario de Navarra, Spain Background & objectives: The One Step Nucleic Acid (OSNA)is a molecular technique for the study of sentinel lymph node (SLN) in breast carcinomas. There is no general agreement on the low- est limit of detection of CK19 expression. A cut-off of 30% is proposed. Methods: We analysed the expression of CK19 in BC diagnosed in our institution since May 2018 and selected those cases with negative or partial expression of CK19. A total of 1189 cases of BC biopsied in our hospital were reviewed, taking the cut-off value of 30%. In the selected cases, tumour type, grade and phenotype were included. Results: 23 cases out of 1189 biopsies (1.93%) showed negative or partial CK19 expression. 19 cases (82.6%) showed less than 30% expression and four cases showed focal positivity >than 30%. 21 cases (91.3%) were invasive carcinoma-NOS with 15 (65.2%) being grade 1 and 2, one metaplastic carcinoma and one solid papillary carcinoma. The most frequent phenotype was luminal A (52.1%). In all cases with minimal and/ or moderate expression (<30%), SLN study by traditional histological examination was recommended. Axillary lymph node metastasis was observed in 6 cases, in which no CK19 expression was verified by immunohistochemistry (IHC). In the 4 cases studied by OSNA, micrometastases was found in 1, CK19 negative. Conclusion: The assessment of CK19 in tumour cells can be challenging in cases with partial positivity. The majority of CK19-negative cases in our series are low-grade tumours, in contrast to previous evidence describing this finding in more aggressive tumours (intermediate-high grade and/or triple negative tumours). A cut-off point of 30% in the assessment of CK19 IHC expression is considered an appropriate value in tumours with partial positivity to perform the OSNA technique, as evidenced in our series. PS-01-007 Gross examination of post neoadjuvant chemotherapy (NACT) breast resections in resource constraint setting – how much is enough? P. Shah*, S. Desai, T. Shet *Tata Memorial Hospital, India Background & objectives: Post-NACT breast carcinoma gross examination poses a challenge when primary tumour is not localized with a radio-opaque wire/clip – a situation common in resource-constrained settings. We undertook a blinded study on two grossing approaches demonstrating how much sampling is adequate. Methods: Fifty breast carcinoma cases were grossed prospec- tively by a single pathologist (n=50). Tumour bed was localized by clinico-radiological and visual correlation only. Tumour bed was submitted entirely in grids of multiple slices (Method 1) and one slice was marked as the one with maximum tumour bed area (Method 2). Kappa values were calculated to evaluate agreement between the two methods. Results: Twenty patients underwent breast conservation surgery; whereas 30 patients underwent mastectomy. Mean of 8 blocks per case were prepared for a single slice (Method 2); whereas 26 blocks were prepared from sampling of entire tumour bed (Method 1). Pathological complete response (pCR) by both methods was calculated to analyse non-pCR cases missed by Method 2. Method 2 documented 23 cases with pCR of which 21 were picked up in Method 1.The two cases missed by Method 2 had minimal residual disease with <2 mm residual tumour (RCB I).The concordance of the two methods was 91.3%. Kappa value for Method 2 was 0.919 thus demonstrating very good correlation with Method 1. Conclusion: Submitting slice of largest visible tumour bed captures 90% of pCR and RCB accurately. In resource-constrained settings, this would be a viable substitute option for primary tumour not localized prior to NACT by radio-opaque wire/clip. The average cost of 1 Hematoxylin and Eosin stained slide is INR.100 (equivalent to approximately 1$). The method 2 was shown to curtail the expenditure to 33%. RCB class could also be assigned using this technique. PS-01-008 Clinicopathological features and response to neoadjuvant chemotherapy in triple positive breast cancer A. Dhaoui*, Y. Houcine, K. Hamza, S. Kammoun, G. Sahraoui, S. Ayadi, R. Chargui, M. Driss *Forces de Securité Interieure, Tunisia Background & objectives: Breast cancers with positive expression of hormone receptor and overexpression of HER2/neu, are called “triple positive breast cancers TPBC”.Data is relatively limited on TPBC. We aim to characterize the clinical and pathological features associated with TPBC and study their responses to neo- adjuvant chemotherapy. Methods: Clinicopathologic data associated with TPBC from 2015 to 2021 were retrieved from our pathology database. A variety of clinicopathologic parameters, including patient age, tumour Nottingham grade, HER2 IHC status, tumour necrosis, and frequency of pathologically-determined complete response to neoadjuvant treatment (PCR). Results: Of 123 consecutive TPBC, all cases were invasive ductal carcinomas. The mean age was 52 years with extremities of 26 and 102 years. TPBCs were more often of Nottingham grade II in 78 cases (63%). TPBC were node-positive in 63 cases (52%) and were less often IHC 3+ in 80 cases (65%). Tumoural necrosis was observed in 78% (n=96). Among the patients that underwent neoadjuvant chemotherapy, PCR was achieved in 3 of 20 (15%) TPBC. Conclusion: In our study, TPBC are associated with Nottingham grade and higher rate of node-positivity. Notably, these tumours show lower rate of complete pathologic response to neoadjuvant chemotherapy. PS-01-009 MMP-2 expression in BC and its association with clinicopatho- logical features and lymph nodes status S62