ECP 2023 Abstracts

S28 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 failed to demonstrate the presence of MelSCs due to their decreased expression. Hence, role of alternative markers like DCT, TRP1, and TYR needs to be explored in order to identify MelSCs. OFP-07-006 Clinicopathological evaluation of nail lesions: a single-centre experience S.K. Dursun*, B. Çalım Gürbüz, O. Erdem, F. Kuşku Çabuk *Basaksehir Cam and Sakura City Hospital, Turkey Background & objectives: The nail region consists of a complex anatomy with surrounding structures. Trauma-induced lesions of this region are frequently confronted in childhood and adulthood. Besides this, infections, systemic disease involvement, and neoplastic lesions are also conditions that can be encountered. Methods: This study aimed to assess the clinicopathological findings in the materials of the patients who had a complaint in the nail area and underwent a biopsy. Biopsy materials of 116 patients diagnosed in our department between June 2020 and December 2022 were retrospec- tively analysed. Clinical presentation type, localization, lesion diame- ter, age, gender, and pathological diagnosis were evaluated statistically. Results: 66% were female and the median age was 30.9 years old (range 6-71). 67%were adults, and 64%were localized to the foot. The most com- mon clinical presentations were; granulation tissue development (58%), keratotic papules (14%), melanonychia (11%). Pathological diagnoses were; vascular lesions (54%), epithelial lesions (22%), infections (12%), stromal lesions (9%), systemic disease involvement (2%). The vascular lesions were seen statistically significantly more frequent in adulthood&toenail region (p<0.001). Among the epithelial lesions, the most common ones were mel- anocytic hyperplasia (n=9) and keratoacanthoma/squamous cell carcinoma (n=6). They were seen significantly higher in adulthood (p=0.01). The sys- temic disease involvement was in adults, while their diagnoses were lichen planus and psoriasis vulgaris. Conclusion: Nail lesions are frequently seen in clinics, but the role of pathology in this process is still unclear. The development of traumatic lesions is the most remarkable condition in the nail region. It is stated that the more frequent occurrence of these lesions is associated with the long-term use of the wrong shoes. Especially in adulthood, hyper- keratotic papules and melanonychia on the nails should be carefully examined clinicopathologically. Systemic disease involvement should also be kept in mind in nail lesions. OFP-07-007 Diagnostic utility of PRAME in melanocytic lesions, particularly in spitzoid ones Z. Gahramanli*, A. Okcu Heper, B.A. Kirmizi *Ankara University School of Medicine, Turkey Background & objectives: Distinguishing between melanoma and nevi is usually straightforward, whereas differential diagnosis can sometimes be problematic. Therefore, additional reliable methods to help differentiate benign from malignant are crucial. We aimed to investigate the role of PRAME in challenging melanocytic lesions. Methods: Our study included 119 cases; 27 atypical Spitz tumours (AST), 12 spitzoid melanoma, 20 conventional melanoma, and 60 nevi (Spitz, melanocytic, dysplastic). All tissue sections were analysed for PRAME, BRAF, BAP1, p16, and MelanA/Ki67. Staining above 75% was accepted as a threshold for PRAME. We also investigated the use- fulness of PRAME together with BRAF(VE1) positivity, Ki67 prolif- eration, p16, and BAP1 loss. Results: PRAME showed diffuse positivity in twelve conventional and three spitzoid melanoma cases. Benign nevi showed no staining at all. However, we detected PRAME expression in one AST, three Spitz nevi, and two dysplastic nevi. For melanoma, sensitivity was 60%, specificity was 100%; for spitzoid melanoma, sensitivity was 25%, and specificity was 100%. When we lowered the threshold to 50%, sensitiv- ity increased to 70% for melanoma and 33.3% for spitzoid melanoma, with no change in specificity. There was no statistically significant correlation between PRAME expression and the degree of dysplasia. However, as the degree of dysplasia increased, the percentage and severity of PRAME expression correspondingly increased. Conclusion: The absence of PRAME staining in melanocytic nevi and its characteristic staining pattern in melanomas demonstrated that PRAME is useful in distinguishing malignant from benign/borderline melanocytic lesions. Furthermore, decreasing the previously reported PRAME cut-off from 76% to 70% in conventional melanoma and 50% in spitzoid melanoma would enhance the sensitivity of PRAME as an ancillary tool. However, a diagnosis based solely on PRAME expres- sion should be avoided, and any expression pattern must be evaluated in light of histologic findings. OFP-07-008 Large-scale dermatopathology dataset for AI: construction, anno- tation, and segmentation of cutaneous neoplastic lesions Y. Chong*, M. Alam, B. Kim, G. Park *The Catholic University of Korea, Republic of Korea Background & objectives: Artificial intelligence (AI) has shown great potential in dermatology and dermatopathology, particularly in seg- menting various cutaneous malignant lesions. However, AI application in dermatopathology mainly focused on malignant melanoma and the dataset was limited without enough external validation. Methods: This study aimed to address previous limitations by con- structing a large-scale, multi-institutional dermatopathology dataset and exploring the potential of AI in segmenting six types of skin lesions. We collected 34,376 whole slide images from multiple medi- cal institutions, including Seoul National University Hospital, Catholic Medical Center, National Cancer Center, and Samsung Medical Center. Multiple segmentation models were employed and compared. Results: Included skin lesions were epidermal inclusion cyst (EIC), seborrheic keratosis, Bowen disease/squamous cell carcinoma (BWN/ SqCC), basal cell carcinoma, melanocytic nevus (MN), malignant mela- noma, normal skin tissue. The model achieved relatively high perfor- mance in segmenting skin lesions, with the highest patch-level perfor- mance of 90.08% in EIC and the lowest of 81.98% in BWN/SqCC, and the highest slide-level performance of 90.78% in MN and the lowest of 81.31% in BWN/SqCC, as measured by dice coefficient score. Conclusion: Our study demonstrates the potential of AI in segment- ing cutaneous malignant lesions using a large-scale, multi-institutional dataset. However, further research is needed to address limitations such as racial diversity and external validation. OFP-07-009 Do multidisciplinary team meetings make a difference in the reporting of dermatopathology? M. Craughwell*, A. Dorman, E. Kay, K. Sheehan *Blackrock Clinic, Ireland Background & objectives: There is increasing evidence around the benefits of multi-disciplinary teams (MDT) in the practice of Histopa- thology. The objectives of this study were to evaluate the impact that dis- cussion at a Dermatopathology MDT had on the final pathology report. Methods: All patients who were listed for discussion at an MDT attended by Dermatologists, Plastic surgeons and Pathologists, between January and December 2022 were analysed retrospectively. The nature of pathology was divided into 3 categories. Any additional work that was performed as part of the 2nd review or MDT discussion was docu- mented, including any changes to the final diagnostic report.