ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Background & objectives: Melanoma accounts for the vast majority of death related to skin cancer. Its incidence increased during the last few decades. The underlying pathogenetic mecha- nisms have to be further elucidated, but several oncogenic muta- tion have been reported to be involved. Methods: This is a retrospective study on 220 melanoma samples (primary or metastatic) from equal patient number. A NGS-DNA Oncomine Focus Assay was performed in all cases. The results are correlated with different clinico-pathological parameters, among which metastatic status and response to therapy. We pre- sent the preliminary results on 114 patients; the study is ongoing. The final results follow upon presentation. Results: The median age at the time of diagnosis was 62,3 years. Less than half of the patients underwent a sentinel node (SN) procedure and 60,87% of the SNs showed metastatic deposits. Distant metastasis was seen in 46,5% of the cases. The metastatic locations ranged from one up to six. Among the mutations, BRAF and NRAS comprised the majority. Patients with a BRAF but no TERTp mutation had more metastatic locations than those with both a BRAF and TERTp mutation (p=0.044). However, the latter had higher rates of brain metastasis than those with BRAF but no TERTp(p=0.037). Patients with NRAS and TERTp mutations displayed a higher Breslow thickness than NRAS alone(p=0.045). Conclusion: We present the preliminary results of our retro- spective study on 114 melanoma samples. We correlated their molecular status with different clinico-pathological parameters. BRAF mutated melanomas seem to can give rise to multifocal metastatic disease, even in the absence of TERTp mutation. How- ever, TERTp mutations are responsible for the more aggressive, brain metastasis. TERTp in combination with NRAS mutation correlates with higher Breslow thickness of the primary tumours. The study is ongoing and final results are about to be completed. OFP-07-002 The utility of PRAME in the diagnostic approach of cutane- ous melanocytic lesions K. De Corte, K. Zwaenepoel, A. Pouliakis, S. Koljenovic, V. Siozopoulou* *Department of Pathology, Antwerp University Hospital, Ede- gem, Belgium Background & objectives: The PReferentially expressed Anti- gen in Melanoma(PRAME) has been extensively researched for its expression in cutaneous melanomas. Yet, little is known about its expression in non-malignant melanocytic lesions. Here we investigate PRAME expression in a large series of cutaneous melanocytic lesions. Methods: We performed a retrospective study on the immunohisto- chemical expression of PRAME in 296 melanocytic lesions. These were classified according to a modified MAPTH-Dx classification in group 1:benign, group 2:moderate atypical, group 3:severe atypi- cal and group 4:malignant. PRAME expression was analysed based on the percentage of cells with expression (< 1%, 1-25%, 26-50%, 51-75%, 76-100%) and on intensity (none/light, moderate, intense). Results: PRAME percentage of 76-100% was seen in 2%, 4%, 11 % and 52% for groups 1 to 4 respectively (p<0.05). Strong intensity was seen in 10%, 9%, 27% and 62% for groups 1 to 4 respectively (p<0.05). The AUC for percentage of PRAME expression in dis- criminating between groups 1 and 4 was 85.09%, between groups 2 and 4 84.90% and between groups 3 and 4 74.61%. The AUC was 64.07% for discrimination between groups 2 and 3, 51.02% between groups 1 and 2 and 63.57% between groups 1 and 3. Comparison of the AUC for percentage, intensity and their combination had no significant difference (p>0.05 in all cases). Conclusion: These results suggest that immunohistochemical analysis for PRAME expression is a useful adjunct for distinguish melanoma from non-malignant cutaneous melanocytic lesions. In the non-malignant category it may play a role in discriminating moderate from severe atypia. The significance of these findings need to be further determined in a larger cohort including the fol- low up clinical data. OFP-07-003 PRAME immunoexpression in 275 cutaneous melanocytic lesions: a single institutional experience G. Cazzato*, A. Colagrande, D. Di Nanni, G. Ingravallo, E. Maio- rano, L. Resta *University of Bari "Aldo Moro", Italy Background & objectives: In recent years PReferentially expressed Antigen in MElanoma (PRAME) has been used in the histopathological diagnosis of melanocytic lesions. We performed a single-centre study to evaluate the data on the usefulness of PRAME could also be confirmed by our group. Methods: From 1 December 2021 to 29/03/2022 we collected 275 cases of melanocytic lesions that were immunostained with PRAME. We categorized PRAME tumour cells percentage positiv- ity and intensity of immunostaining in a cumulative score obtained by adding the quartile of positive tumour cells (0,1 +, 2 +, 3 +, 4 +) to PRAME expression intensity in tumour cells. Results: Of these 275 lesions, 136 were benign, 12 were of uncer- tain potential for malignancy, and 127 were malignant. The immu- noexpression of PRAME was totally negative in 125/136 benign lesions with only a few positive melanocytes, with intensity 1+ in the remaining 11 cases (8.1%). Of the 127 cases of melanoma, PRAME was strongly positive in 104/127 cases with intensity 4+ and 3+. In 17 cases PRAME was positive in percentage 2+ and with intensity ranging from 2+ to 3+. In 6 cases of desmoplastic melanoma, PRAME was 1+ positive or completely negative. Of the 12 cases of spitzoid lesions, PRAME was much more hetero- geneous and irregularly distributed throughout the lesion. Conclusion: These data are perfectly in agreement with the current literature, they demonstrate that the reliability of PRAME is quite high, but its use cannot disregard the morphological information and the execution of other ancillary immunohistochemical stains such as Melan-A, HMB-45, MiTF and SOX-10. OFP-07-004 Cutaneous histopathological findings in systemic amyloidosis B. Yaman, C.A. Gomez Gonzalez*, A. Acar, T. Akalın, B. Sarsık Kumbaracı, A. Çeltik, S. Şen *Department of Pathology, Medical Faculty, Ege University, Izmir, Turkey Background & objectives: Amyloidosis comprehends a group of diseases characterized by the deposition of amyloid fibres within tissues and organs. Skin biopsy is a simple and safe procedure with a high yield and might be used to support the diagnosis of systemic amyloidosis. Methods: We analysed 59 skin biopsies from 47 patients with sys- temic amyloidosis (SA) (26 males, 21 females), including 18 amy- loid light chain (AL); 19 serum amyloid A (AA), and 10 non-AL/ non-AA amyloid types. We evaluated the distribution of amyloid deposits within the tissue. Results: For each group of systemic amyloidosis, AL, AA, and non-AL/non-AA type, secondary cutaneous amyloidosis was con- firmed in 15 (83,3%), 6 (31,5%), and 6 (60%) cases respectively. S28