ECP 2023 Abstracts

S156 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 fulfilled the inclusion criteria. Survival analysis used the Kaplan-Meier method. Results: All 23 patients were women, with a median age of 56 years- old (38-88), the majority postmenopausal (n=15, 65%). Regarding tumours’ characteristics, 20 patients (87%) had G3 tumours and the remaining G2. All had Ki67% > 20%. Most patients were initially treated with a curative intent (n=19, 82%) and only 4 were stage IV at diagnosis. Twelve patients (52%) had neoadjuvant chemotherapy, with pCR in 2 patients. Adjuvant chemotherapy was done in 10 patients. AR were positive in 5 patients (21%). Median OS was 6.8 months, with a median follow up time of 5.8 months. As there were only 5 patients positive for AR, the positive and negative populations weren’t compared. Conclusion: AR expression was rare in our population of metastatic patients. The low number of positive patients didn’t allow for comparison of OS. This low prevalence is in line with previously reported values (approximately 30%). Patients without other treatment options should be tested for AR expression in cases where the attending oncologist con- sidered using off-label anti-androgen medications. In this old dataset, survival of TNBC patients was dismal, with a median OS of <7 months, while recent studies show much higher survival. J. Boavida and I. Pinho have both contributed equally to this study. E-PS-02-015 Lymph node involvement in pure ductal carcinoma in situ is rare (DCIS): a study of 575 breast resections with pure DCIS and quan- tification of sampling M. Bonert*, F. Mrair, P. Williams *McMaster University / St. Joseph’s Healthcare Hamilton, Canada Background & objectives: Lymph node positivity with pure DCIS is noted to be 0-4.9%; however, many of these studies are older. We performed a retrospective analysis of in-house breast excisions focused on reported pure DCIS cases and quantified the tissue sampling. Methods: All in-house breast cancer cases (2011–2020) at two institu- tions with a synoptic report were extracted along with the total block count per case. DCIS cases were reviewed, and "pure DCIS" cases excluded all post-neoadjuvant, and encapsulated/solid papillary car- cinomas. Lymph node (LN) status was determined in the selected (DCIS) cases, based on the pN stage as reported in the synoptic. Results: The study period included 4,292 cases with an invasive breast cancer synoptic (IBCS) and 622 with a DCIS synoptic. 575 of 622 cases remained after the exclusions. 70% (400/575) did not have any axillary LN sampling. DCIS cases that had axillary LN sampling were larger (Mean: 41.2mm, vs 23.6mm), higher grade (43% Grade 3 vs 30%), associated with comedonecrosis (69% vs 55%) and more fre- quently mastectomies (56% vs 15%). Only one case (of the 175 that had LN sampling) had a LN metastasis on excision. The 25%, 50% and 75% block counts were: 29, 41 and 55 for IBCS, and 26, 40 and 57 for the 575 included DCIS cases. Conclusion: Lymph node metastases in the pure DCIS cohort exam- ined are exceedingly rare with the local sampling practices. Sampling of breast specimens is likely a significant determinant of the diagnostic classification and should be examined in the context of resource use. The ratio between DCIS only cases to invasive breast cancer cases in conjunction with sampling metrics may be useful to compare insti- tutional practices, assess the reproducibility of diagnostic classifica- tions, optimize resource expenditures and improve our understanding of breast cancer. E-PS-02-016 Primary melanoma of the breast parenchyma versus cutaneous mammary melanoma. How to diagnose to improve outcomes – case series L. Bosoteanu*, M. Aschie, M. Bo ș oteanu *Department of Dermatology, “Elias” Emergency University Hospital, Bucharest, Romania, Institute of Doctoral Studies, Doctoral School of Medicine, “Ovidius” University of Constanţa, Romania Background & objectives: Cutaneous mammary melanoma accounts for <5% of all melanomas, while primary melanoma of the breast parenchyma (PMBP) is exceptionally rare, with <20 cases reported. This study aims to highlight the pathologist’s arsenal essential to cor- rectly distinguish between these two conditions. Methods: In this case series, we present two patients with mammary melanoma of different tissue origins who were treated at our institu- tion. Patient 1 was a 36-year-old female with cutaneous right mammary melanoma, while patient 2 was a 60-year-old female with melanoma of the left breast parenchyma. Results: Patient 1 underwent surgical excision of the non-ulcerated superficial spreading melanoma with a Breslow index of 1.6 mm. Sen- tinel lymph node biopsy identified a tumoral deposit, thus integration in stage IIIA imposed the combined Dabrafenib-Trametinib treatment. Dermoscopy highlighted the presence of 100 typical and atypical nevi; dermatological follow-up is currently practiced quarterly. The left upper-outer quadrantectomy sample of patient 2 microscopi- cally displayed clusters of atypical melanocytes between the mammary glandular structures, without junctional activity. S100 and Melan-A were positive, with a Ki-67 rate of 70%. Comprehensive full-body muco-cutaneous examination unveiled no melanocytic lesions, authenticating the melanocytic lesion’s primary breast origin. BRAF V600mut status imposed administration of Vemurafenib, with note- worthy efficacy. Conclusion: In conclusion, our 2 cases highlight the challenges and polymorphism implied by the histopathological differential diagno- sis between cutaneous melanoma of the breast and PMBP, as well as the importance of immunohistochemistry. Careful diagnostic consid- eration is pivotal in regard to therapeutic methods. Surgical excision remains the mainstay of treatment in both contexts, but the aggres- sive and unforeseeable biological behaviour of PMBP commonly requires the use of adjuvant treatments (immunotherapy or anti-BRAF medications). E-PS-02-017 Invasive papillary carcinoma of the breast. A report of four cases A. Canino*, A. Ravarino, C. Gerosa, R. Murru, J. Caschili, P. Baldussu, D. Fanni *Department of Medical Sciences and Public Health, University of Cagliari, Italy Background & objectives: Invasive Papillary Carcinoma (IPC) is an exceedingly rare type of breast cancer since no specific data are avail- able. Within the last ten years, we have observed IPCs only in 4 out of 1004 invasive breast cancers in routine diagnosis. Methods: The ages of those patients ranged between 67 and 86 years old. Samples taken from the surgical specimen were formalin-fixed, paraffin-embedded, and stained for H&E stain and the following immu- nohistochemistry analysis: p63, Cytokeratin 5, Cytokeratin 7, GATA-3, Oestrogen and Progesterone receptors, Her2/Neu, Ki-67 (MIB-1). Results: Histologically, the tumours presented an invasive pattern characterized by papillae supported by fibrovascular cores, covered by epithelial cells with moderate atypia. Immunohistochemistry showed positivity for GATA 3 and Cytokeratin 7, confirming the mammary origin of the tumours. Cytokeratin 5 and p63 were negative in the pap- illary fronds and at the periphery of the lesion, excluding other papil- lary neoplasms and leading to the diagnosis of IPC. The positivity for oestrogen receptors was between 90% and 100%, while the positivity for progesterone receptors was between 95% and 5%. Her2/Neu Score was 0 in 3 cases since only one was 2+. The ki-67 index was between 15% and 35%.