ECP 2023 Abstracts

S187 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 A Marjolin’s ulcer is a rare and aggressive cutaneous malignancy developing within sites of previously-injured skin, scars, and chronic wounds. (French surgeon/pathologist Jean-Nicholas Marjolin). The most common malignancy is SCC. Burn scars are the most common underlying aetiology. Tumours have also been reported to arise in; trau- matic wounds, osteomyelitis, venous ulcers, pressure ulcers, radiation dermatitis, stings, hidradenitis suppurativa, and inflammatory disor- ders. The lower extremity is most frequently affected. Conclusion: We have described the rare case of an acute extensive 21cm Marjolin’s ulcer (SCC) unusual in its development within one year of injury. In the chronic form ( >1 year from injury) the average duration to malignant transformation is more than 30 years. Presenta- tion within five years of injury, and with an exophytic formation as in this case are regarded as positive prognostic indicators. Aggressive management and close clinical follow-up is required due to the high- risk of recurrence and metastasis. E-PS-05-030 A case report: balloon cell malignant melanoma K. Kurt*, A. Orgen Calli *Izmir Katip Celebi University, Ataturk Training and Research Hospi- tal, Department of Pathology, Turkey Background & objectives: Balloon-cell malignant melanoma (BCMM) is rare variant composed of foamy cells with abundant cyto- plasm causing ballooning of cells. These features can also be seen in balloon cell nevus. Nevertheless, nuclear pleomorphism, mitoses, and lack of melanocyte maturation help differentiate BCMM. Methods: Histomorphological features were assessed with hematoxy- lin-eosin sections in view of macroscopic and clinical features. Addi- tionally, immunohistochemical stains were used during the process. Results: A tumour excision was planned for a 49-year-old female patient who presented with 1.3 cm diameter pigmented lesion on the back, which has been present for one year. Macroscopically, a 1.3 cm diameter slightly elevated lesion with hyperpigmented was observed on the skin. Histopathologically, in the dermis, an asymmetric tumour area that forms nesting structures and also spreads as a single atypical mel- anocytes was observed. Tumour cells had nuclear pleomorphism and abundant clear/eosinophilic granular cytoplasm. The foamy cells in the superficial dermis extend to fatty tissue. In the intradermal component, there was mitosis and a lack of maturation of melanocytes. Immuno- histochemically, HMB-45 and melan-a were positive in balloon cells. Conclusion: BCMM is a very rare histopathological subtype of malig- nant melanoma challenging for pathologists. Balloon cell changes can be seen in many neoplasms, including malignant melanoma. Although there are many compelling entities in the differential diagnosis, know- ing the characteristic features of BCMM will reduce the risk of misdiagnosis. E-PS-05-031 Lymphangioma-like Kaposi sarcoma: a clinicopathological study of 2 cases E. Kuzucular*, F. Özden *Istanbul Medipol University, Turkey Background & objectives: Lymphangioma-like Kaposi sarcoma (LLKS) is a rare histologic presentation of Kaposi sarcoma (KS). We report two cases with clinical and histopathological features. Methods: In our hospital, there were 41 cases diagnosed with Kaposi Sarcoma (KS) between 2014 and 2022, two of which were in LLKS morphology. Immunohistochemically anti-human herpesvirus-8 (HHV- 8), anti-CD34, and D2-40 antibodies were tested. Results: Of the total of 41 cases of KS in skin biopsy specimens, only 2 cases showed LLKS. Both patients were male and in the advanced age group (75 and 81). Clinically, each patient presented with violaceous patches, papules, or plaques. One patient also had an actinic keratosis. All of the LLKS biopsy specimens revealed areas with characteristic light microscopic features of KS. Lymphangioma-like areas comprised ectatic, irregularly shaped vascular spaces lined by mildly atypical endothelial cells. All tumour cells showed strong and diffuse reactiv- ity for anti-HHV-8, anti-CD34, and D2-40. KS progressed slowly in two patients with adequate follow-up. Conclusion: Lymphangioma-like Kaposi sarcoma may cause diffi- culties in differential diagnosis with other vascular tumours. In these cases, definitive diagnosis relies on recognition of the distinctive clini- cal and histological features of KS, including a strong immunohisto- chemical expression of HHV-8 in lesional cells. E-PS-05-032 BRAF mutation in primary and metastatic melanomas L. Lozneanu*, I.D. Căruntu, C. Amalinei, R. Balan, S.E. Giu ș că, A. Rusu, E.R. Avadanei *U.M.F. "Grigore T. Popa" Iasi, Romania Background & objectives: Our study aims to evaluate the correlation between the BRAF mutation and the stages of melanoma progression, highlighting the difference between the BRAF mutation frequency in primary versus metastatic melanomas. Methods: 38 and 24 cases with primary melanomas and metastatic melanomas, respectively, were analysed. Tumour biopsy samples from melanoma patients were analysed, in order to determine the BRAF mutation frequency, using fully automated IdyllaTM BRAF Mutation Test (Biocartis, Mechelen, Belgium). All analyses were performed using the MedCalc statistical package. Results: We evaluated biopsies from a number of 62 patients diagnosed with malignant melanoma, 38 of primary tumours located in the skin (35 cases - 92.10%) and in the oral mucosa (3 cases - 2.63%), and 24 presented secondary tumours with lymph node location (20 cases - 83.33%) liver (1 case - 4.16%), lung (1 case - 4.16%), parotid (1 case - 4.16%), and intestinal (1 case - 4.16%) location. BRAF mutation was present in 21 of 38 (57.89%) patients with primary melanoma and in 10 of 24 (54.16%) patients with metastatic melanoma. Conclusion: Our results demonstrate the relationship between mela- nomas and BRAF mutation without differences between primary and metastatic melanomas. This feature suggests that BRAF mutation in melanoma occurs, most likely prior to metastatic disease and supports a characteristic of the initial pathological process. E-PS-05-033 Artificial intelligence shows pathologist-level detection of sentinel node metastases of malignant melanoma N. Neittaanmäki*, J. Siarov, D. Kumar, J. Paoli, J. Mölne *Department of Laboratory Medicine, Institute of Biomedicine, Sahl- grenska Academy, University of Gothenburg, Gothenburg, Sweden Background & objectives: Detection of nodal metastases (NM) in sen- tinel node biopsies (SNB) is a crucial part of melanoma staging. Benign intra-nodal nevus (INN) may be misclassified as NM. We assessed the capability of artificial intelligence (AI) in detection of these two entities. Methods: In total 495 hematoxylin and eosin whole-slide images (WSIs) including NM and INN from 233 SNBs were collected and divided into training (288 WSIs), validation (89 WSIs) and test sets (118 WSIs). The deep learning algorithm was trained with 5956 pixelwise annotations. The test set was assessed by the AI and three blinded dermatopatholo- gists. Immunohistochemistry served as the reference standard. Results: The AI model showed excellent pathologist-level performance with the area under the receiver operating characteristic (AUC) of 0.965 for detection of NM. For comparison, AUC for the pathologists for NM detection varied between 0.944-0.978. For detection of INN, AUC was lower for both AI (0.781) and the pathologists (range 0.627-0.790).