ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 and nuclei. Macrometastases, up to 13x8 mm, were present in 3 of 15 dissected axillary nodes. Immunohistochemically, primar y and metastatic carcinoma cells were diffusely positive for chromogranin A and the oestrogen receptor. HER2 was negative, and the MIB-1 index was 36.2%. Band-like expressions of MUC1 and EMA were noted on the stroma- facing surface of the carcinoma cell clusters. Conclusion: Some investigators recently reported that NEN is a distinctive type of aggressive IBC. Multivariate analyses have revealed that, in patients with mammary NENs, overall survival can be predicted by tumour size, nodal status, and the MIB-1 proliferation rate. Our present patient with an unusual breast cancer showing both invasive micropapillary and neuroendocrine features developed plural lymphoglandular metastases as well as having a tumour with a large diameter and luminal B-like immuno-profile. Accordingly, meticulous clinical follow ‐ up is essential for this case. Funding: Tomonori Kawasaki is supported by Grants-in-Aid for Scientific Research (No. 21K06910 and No. 20K08131) from the Japanese Ministry of Education, Culture, Sports, Science and Technology and the National Hospital Organization (NHO) Grant (H29-NHO-01). E-PS-02-003 Morphologic and immunohistochemical features of triple nega- tive breast cancers: a tissue – microarray study R. Lobrano, P. Paliogiannis*, M.A. Piras, V. Marras, M.A. Fedeli, A. Fara, A. Cossu *Unit of Anatomic Pathology, Italy Background & objectives: Triple negative breast cancers (TNBC) are the most aggressive breast cancer subtypes according to the Sain Gallen classification. The aim of the present study was to evaluate the immunohistochemical features of TNBC in relation with their histo- pathological characteristics. Methods: Consecutive invasive breast cancer cases diagnosed from 2005 through 2013 were included. All tumours were re-examined and classified in accordance with the Saint Gallen classification criteria. Immunostaining with tissue micro-array was performed in all TNBC with Ventana BenchMark Ultra system with antibodies for E-cadherin, Ki67, Cytokeratin 17, Cytokeratin 14, Cytokeratin 5/6, MUC1, Androgen receptors, IgF1R, p53, Claudin, VEGF, and PD-L1. Results: Globally, 2572 cases with a mean age of 59 years were examined, and among them 199 (8%) were identified as TNBC; 4 were excluded because they were not Sardinians. Therefore, 195 TNBC patients were analysed. At t he time of diagnosis, most of them had a ductal NOS breast carcinoma (DBC, 109, 55.8%), 112 (57.4%) had a T2 or greater disease stage, but 108 (52.8%) had no axillary lymph node involvement. The grade of the disease was G3 in 146 (74.8%) cases. Considering the expression of the biomarkers analysed, seven TNBC subtypes were identified: cytokeratin negative DBC, basal-like DBC, apocrine cancers, medullary cancers, pleomorphic lobular cancers, anaplastic cancers, and metaplastic tumours. Conclusion: TNBC show a wide range of specific morphological and immunohistochemical features, which characterize subgroups with different biological and clinical behaviour. Knowledge of these features are essential for correct diagnosis and treatment of patients with TNBC. E-PS-02-004 Mammary Paget’s disease mimicking in-situ melanoma – a case report and review of literature L. Bosoteanu*, M. Aschie, M. Bosoteanu *Department of Dermatology, “Elias" Emergency University Hos- pital, Bucharest, Romania Background & objectives: Mammary Paget’s disease (MPD), in-situ breast carcinoma, a scarce histological condition, accounting for 1-4% of female breast cancers, may appear either independently, or in conjunction with an invasive carcinoma (~90%). The immunophenotype generally comprises, among others, positivity for HER2. Methods: We report the case of a 44-year-old female patient, presented with a rash of the nipple accompanied by a right mammary mass, previously identified on digital mammography. The microscopical examination and immunohistochemical profile were consistent with MPD associated with invasive breast carcinoma (NST), the former particularized by an infrequent negative reaction for HER2, while oestrogen receptor was positive. Results: Herein, the histopathological and immunohistochemical approach derived from the exigency of excluding the possibility of synchronous tumours: a mammary invasive carcinoma, accompanied by another component with MPD phenotypic mimicry. The unexpected negative HER2 reaction conducted to a primary focus on excluding a malignant melanoma in situ. The absence of MelanA and S100 expression, lack of pigmentation and clinical aspects infirmed it. Bowen’s disease was invalidated by its rare presentation in the breast cutaneous tissue and the absence of individual risk factors suggestive of a pre- existent immunosuppressive status. In case of similar morpho- immunohistochemical aspects, high expression of Ki-67 signals MPD, an immunoreactivity that helped distinguish the cellular population from Toker cells. Conclusion: MPD’s global pattern may provoke to diagnostic pitfalls, due to the occasionally polymorphic immunoreac- tions and its ambiguous clinical presentation. The current case highlights an unusual biomarker profile of MPD – overexpres- sion of oestrogen receptor and HER2 negativity, an associa- tion only encountered in 6% of the cases. Thus, the utmost importance of immunohistochemistry is reflected in its abil- ity to segregate between different lesional entities and in its prognostic significance, being geared towards extending the therapeutic arsenal. E-PS-02-005 Malignant solitary fibrous tumour of the breast: a rare tumour in a rare location S. Reis*, N. Castelo-Branco, L. Rei, C. Abrantes, A. Coelho, P. Figueiredo *Department of Pathology, Instituto Português de Oncologia de Coimbra Francisco Gentil EPE, Portugal Background & objectives: Solitary fibrous tumour (SFT) is an uncommon mesenchymal neoplasm most often found in the pleura. Breast malignant SFTs are extremely rare, being this case the third reported so far. Methods: We present a case of a 79 year-old woman with a 2 cm tumour on the upper quadrants of the left breast (BI-RADS-4C). The core biopsy revealed a CD34+ mesenchymal tumour of low malignant potential (EWGBP-B3). The patient refused surgery. After four years, the size of the breast mass was 8 cm and was adherent to deep soft tissue. S191