ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 PS-10-009 Does MYC-amplification help distinguishing primary from radiation-induced angiosarcomas? B. Raposo Pulido*, J.M. Rodríguez Barbero, F.I. Camacho Castañeda, A.E. Ballén Barragán, M. Granados Almillo, J.P. Morillo Morillo, R. Granados Carreño *Hospital Universitario de Getafe, Spain Background & objectives: Angiosarcomas (AS) can be primary (PAS) or secondary (SAS) to radiation therapy or chronic lymphedema. Both share histological findings, but genetic and molecular differences have been reported. We compared these features in 8 cases of AS. Methods: We retrospectively reviewed 8 cases of AS (4 males and 4 females) diagnosed at our hospital between 1996 and 2022. Clinicopathological, immunohistochemical (IHC) and molecular studies were performed in 5 cases of PAS and 3 of SAS. Results: Eight patients with an age range of 18-79. Three had SAS 3-30 years after irradiation for breast carcinoma (2 cases) or brain astroblastoma. Five PAS were from the skin, breast, pleura, popliteal artery and penis. Histopathological study revealed a high-grade malignant mesenchymal tumour with pro- liferating endothelial cells and varying degrees of atypia and growth patterns (epithelioid, spindled, or vasoformative) in all cases, not distinguishing PAS from SAS. p53 overexpression was seen in all 5 PAS, but it was absent in the 3 SAS cases. While c-myc overexpression was demonstrated by IHC in all but the penile AS, only 3 PAS and 1 SAS showed low-level MYC amplification (3-5 copies). Conclusion: In our study, c-myc immunohistochemical overex- pression did not correlate with MYC gene amplification in all the cases. Low-level MYC amplification was found in 50% of our cases. Interestingly we couldn’t demonstrate high-level MYC amplification (>10 copies) in any case. In our series, MYC and/ or p53 alterations may play an important role to induce oncogen- esis in AS, independently of prior radiation therapy, by increas- ing genomic instability. PS-10-010 Usefulness of novel SS18-SSX and SSX c-terminus antibodies for identification of specific fusion oncoprotein in sarcomas T.M. Godschachner*, J. Igrec, S. Scheipl, A. Leithner, B. Liegl- Atzwanger, I. Brcic *Medical University of Graz, Austria Background & objectives: Chromosomal rearrangement can be iden- tified by direct methods or immunohistochemical staining for a compo- nent of the fusion oncoprotein as a surrogate marker. We aim to gain insights into the staining profile of sarcomas using novel SS18-SSX and SSX c-terminus antibodies. Methods: Retrospective analysis of 303 soft tissue sarcomas diagnosed at our Institution between 1999 and 2019 was per- formed, and tissue microarrays were constructed. Immunohisto- chemistry was conducted on the Benchmark Ultra platform with iVIEW DAB Detection Kit. Two different antibodies for SSX locus were used: SS18-SSX and SSX c-terminus. Ten whole- tissue sections of genetically confirmed synovial sarcomas were used as a control. Results: In total, 19/303 (6.3%) and 23/303 (7.6%) sarcomas showed in most of the cases strong nuclear staining with SS18- SSX and SSX, respectively. In detail, from 21 synovial sar- comas, 19 (90.5%) stained positive for both antibodies. In 5 cases, nuclear staining for SSX antibody was weak. 9/10 (90%) control cases showed strong nuclear staining for SS18-SSX, and 3/10 (70%) were negative for SSX. Furthermore, SSX nuclear expression was also found in 4/56 (7.1%) myxofibro- sarcomas. All other sarcomas, including various liposarcomas, angiosarcomas, undifferentiated pleomorphic sarcomas, leio- myosarcomas, and epithelioid sarcomas, were negative for both antibodies. Conclusion: Novel SS18-SSX and SSX c-terminus antibodies are reliable diagnostic markers and can be used as surrogate markers to identify a specific fusion. The former antibody is more specific and shows strong nuclear staining in synovial sarcomas, whereas SSX can present with weak staining and is less specific. RNA-based NGS analysis should be performed in equivocal cases to confirm the specific rearrangement. PS-10-011 Chordoma: significance and correlation of the localisation, vascular density and Ki67 for the occurrence of chordoma recurrence L. Simic*, J. Jevtic, M. Radojevic, D. Ribic, S. Rajkovic, G. Dju- ricic, D. Ristic, J. Sopta *University of Belgrade, Faculty of Medicine, Institute of Pathol- ogy, Belgrade, Serbia Background & objectives: Chordomas are malignant slow-growing, locally invasive tumours, usually localized in sacrum, vertebra and scull base, characterized by frequent relapses. The aim of the study is to examine the correlation between localization, blood vessels density and Ki67 value and disease recurrence. Methods: All chordoma biopsies, taken in Institute for Orthopaedic Surgery Banjica in the period of five years (2017-2021), were analysed at the Institute of Pathology, in Belgrade. A total number of 21 cases were divided into two groups: patients with and without relapses. Ki67 value was counted on 100 cells in hot spot. Vascular density was estimated using CD34 immunostaining in 1mm2. Results: Out of total 21 patients with chordoma only 9 had a relapse. The most affected bone was sacral bone, but without a statistically significant difference in the frequency of recurrence at different chordoma localizations. The average number of blood vessels in 1mm2 and value of Ki67 was statistically significantly higher in group of tumours with recurrence (p=0,015, p=0.033 respectively). Ki67 proliferative index values greater than 10% show a statistically significant difference in the frequency of relapses. The value of the proliferative index higher than 15% has a moderately high correlation with the occurrence of relapse. Conclusion: Chordoma is a rare, but locally aggressive tumour, with high recurrence rate (35-40%). Based on our results, determination of the immunohistochemical expression of CD34 antigen in evaluation of vascular density, together with proliferative index Ki67 can be helpful to predict tumour recurrence. PS-11 | Poster Session Cytopathology PS-11-001 Pancreatobiliary cytopathology: the use of the Papanicolaou Society system in the transition towards a new era of stand- ardised reporting M. Hanks*, G.P. Aithal, A.M. Zaitoun *Nottingham University Hospitals NHS Trust, United Kingdom Background & objectives: Modern diagnostic techniques have allowed for a less invasive approach to pancreatic cytopathology S121