ECP 2023 Abstracts

S29 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Results: 431 patients were discussed at MDTs over the 12-month period, including melanocytic (47%), non-melanocytic neoplasia (27%) and inflammatory lesions (26%). After 2nd review/MDT dis- cussion, 155 (36%) of these required further investigation including 102 requiring additional immunohistochemistry/special stains, 5 molecular analysis and 7 external opinions. Of the 155 requiring investigation, this did not change the final conclu- sion in 67 (43%), but half these reports required supplementary clarifi- cations. In the remaining 88 (57%) where discrepancies were identified, this included measurement of margins (28%), a change in grade of atypia/depth of invasion (24%), including upgrading from benign to malignant or vice versa (10%). The final diagnosis was altered in 9% of inflammatory lesions. Conclusion: This study confirms the value of 2nd review and MDT discussion in improving the diagnostic accuracy of Dermatopathology reporting. In particular, melanocytic lesions required more additional work (59%) in comparison to non-melanocytic neoplasia or inflamma- tory pathology. Further studies are required to assess how the changes identified reflect the overall clinical management of these patients. OFP-07-010 Collagen V mediates the fibrillar organisation in the time course of skin fibrosis in experimental systemic sclerosis Z.A. de Jesus Queiroz, A.P. Pereira Velosa, J. Sampaio Silva, S. Cata- nozi, A. dos Santos Filho, S. de Morais Fernezlian, V. Elias Contini, L.K. Ramos da Silveira, S. Carrasco, V. Berton Liguori Zacchi*, D. Levy, V.L. Capelozzi, W. Rosolia Teodoro *Division of Rheumatology, Faculdade de Medicina da Universidade de São Paulo, Brazil Background & objectives: The formation of cutaneous fibrosis in the Systemic Sclerosis (SSc) model induced by collagen V (Col V) remains unknown. Our objective was to characterize skin fibrosis in this model and to evaluate the effect of Col V in fibroblast culture. Methods: SSc model was induced in C57BL/6 mice by Col V immu- nization. The animals were euthanized on 15-, 30-, 45-, and 120-days post-immunization. Histology, immunofluorescence, and histomorpho- metry were employed to evaluate cutaneous fibrosis. The synthesis of fibrillar collagens I, III, V, and α-SMA in healthy mouse skin fibro- blasts stimulated with 25,50, 100μg/mL of Col V was evaluated by immunofluorescence. Results: The temporal analysis showed an increase of collagen I expression in the 45- and 120-days groups in comparison with the 15 and 30 (P<0.01) days groups. Furthermore, we observed a significantly increased expression of collagen III in the skin from 120 days group compared to the 15, 30, and 45 (P<0.01) days groups. Additionally, 45 and 120 days, showed a significant increase in collagen V (P<0.01). Fibroblasts stimulated with Col V showed increased expression of col- lagen I and α-SMA (P<0.05), collagen III, and collagen V (P<0.01). Conclusion: Our study indicates that the increase in Col V alters skin fibrillogenesis, contributing to the onset of the cutaneous fibrosis pro- cess in the SSc model, after 45 and 120 days of immunization. In addition, Col V in vitro stimulates fibroblast differentiation and col- lagen production. These data suggest that Col V stimulates a signalling pathway that could result in fibrosis. This work was supported by the Sao Paulo Research Foundation - FAPESP [Process numbers: 2018/20403-6, 2018/00415-0, and 2021/13220-5] and Foundation Faculty of Medicine. OFP-07-011 Immunohistochemistry of NTRK in atypical fibroxanthoma and pleomorphic dermal sarcoma: a five-year study N. Cadavid-Fernández*, A. Tenelanda-Santillán, M.R. Meléndez Gispert, C. Ariño-Palao, A. Veliz Dominguez, S. Foncueva-Casado, D. Bueno-Sacristán, A. Navarro-Cantero, C. Perna-Monroy, M.E. Reguero-Callejas, C. Moreno-Garcia-del-Real *Ramón y Cajal University Hospital, Spain Background & objectives: Atypical fibroxanthoma (AFX) and pleo- morphic dermal sarcoma (PDS) are spindle-shaped malignant cutaneous neoplasms (clinicopathological spectrum) of mesenchymal origin. We propose that they may present NTRK fusions as the new emerging group of soft tissue tumours called NTRK-rearranged spindle cell neoplasms. Methods: All AFX/PDS diagnosed at our institution (January 2018- March 2023) were collected, reviewed and stained with pan-TRK anti- body (clone EPR17341). We evaluated the presence or absence of stain- ing and the percentage of positive tumour cells. Positive staining was defined as staining above background in at least 1% of tumour cells in any pattern including membranous, cytoplasmic, perinuclear or nuclear. Results: We studied a total of 21 cases diagnosed as AFX/PDS [16 (76%)/ 5 (24%)]. Four (19%) were punch biopsies and 17 (81%) were complete excisions. Pan-TRK (+) was positive in 4 (19%) cases, with medium intensity cytoplasmatic and focal expression pattern in spin- dle-shaped cells; 3 (14%) cases were considered to have borderline positivity for pan-TRK defined as mild cytoplasmatic positivity not clearly in spindle-shaped cells and the remaining cases were negative. The 4 positive cases were FXA and among the borderline cases 2 were diagnosed as PDS and 1 as FXA. In positive/borderline cases we will perform molecular techniques (FISH) to support our results. Conclusion: AFX/PDS tumours develop in sun-damaged skin of the elderly. They both are diagnosis of exclusion and their treatment is sur- gical tumour extirpation except in high-risk cases in which multidisci- plinary treatment is considered. After reviewing the literature, possible NTRK fusions justified by their spindle-shaped morphology have not been studied. We carried out this study not for diagnostic purposes but to analyse possible new molecular associations and treatment targets. OFP-07-012 SATB2, CKAE1/AE3, and synaptophysin as a sensitive immuno- histochemical panel for the detection of lymph node metastases of Merkel cell carcinoma – a multicentre study P. Donizy*, D. Massi, A. Cassisa, M. Krzyzinski, M. Dudzisz- Sledz, P. Biecek, P. Rutkowski, A. Marszalek, M.P. Hoang, A. Szumera-Cieckiewicz *Department of Clinical and Experimental Pathology, Wroclaw Medi- cal University, Poland; Department of Pathology and Clinical Cytol- ogy, Jan Mikulicz-Radecki University Hospital, Wroclaw, Poland Background & objectives: This study was undertaken to determine the most sensitive immunohistochemical panel for the detection of nodal metastases in Merkel cell carcinoma (MCC) patients. Methods: 102 metastatic MCC lymph nodes were tested with 7 anti- bodies, including cytokeratin (CKAE1/AE3), CK20, chromogranin A, synaptophysin, INSM1, SATB2, and neurofilament (NF). The 5-tier scoring system was used for analysed markers (0: 0% of positive MCC cells; 1: <25%; 2: 25-74% ; 3: 75-99%; 4: 100% of MCC cells with moderate to strong reactivity). Results: SATB2, CKAE1/AE3, and synaptophysin are the top three markers with the highest cumulative percentage of positive reaction. 91/102 (89.2%) of metastatic nodes were characterized by a moderate to strong expression of SATB2 in ≥75% tumoral cells; 85/102 (83.3%) and 80/102 (78.4%) for CKAE1/AE3 and synaptophysin, respectively. There were no entirely nega- tive cases for these markers. SATB2 and CKAE1/AE3 were the stains with the highest rate of 100% positivity. SATB2 and CKAE1/AE3 presented a significant additive effect on detecting MCC metastases. 10/11 (91%) of SATB2-lowmetastatic lymph nodes revealed high CKAE1/AE3 expression. Fisher’s exact test showed the similar distribution of SATB2, CKAE1/AE3 and synaptophysin among MCPyV-negative and MCPyV-positive cases.