ECP 2023 Abstracts

S185 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Background & objectives: CRTC1::TRIMM11 cutaneous tumour is a new entity in the 5th edition of WHO classification. It commonly occurs in the extremities of patients of various ages. Although they are expected to behave indolently, the scarcity of cases makes this uncertain. Methods: We present the case of a 14-year-old girl with a 1 cm exo- phytic nodular lesion on the shoulder that was clinically suspected to be a sweat gland tumour. The lesion was excised for pathological examination. In addition to light microscopy, immunohistochemical analysis (IHC-a), fluorescence in situ hybridization (FISH) and Next- generation sequencing (NGS) were performed. Results: Histopathological analysis revealed a spindle-cell tumour in the dermis with a well-circumscribed border. The tumour cells had large cytoplasm without pigment, and some of them had conspicuous nucleoli. They were arranged in intersecting fascicles, with striking fibrous bundles weaving in between them. The mitotic rate was very low and atypical forms were not observed. The differential diagnoses included melanocytic tumours and dermal clear cell sarcoma. IHC-a demonstrated focal S100 and diffuse SOX10 positivity. Melan-A, HMB45, PRAME, PANTRK, and BRAF-VE1 were negative. EWSR rearrangement was investigated using a break-apart FISH probe and the results were negative. RNA sequencing using NGS revealed a CRTC1::TRIMM11 translocation. Conclusion: Dermal tumours with a differential diagnosis of clear cell sarcoma or metastatic melanoma with SOX10 expression and negative EWSR rearrangement, should raise suspicion for CRTC1::TRIMM11 cutaneous tumour. We believe that with increased awareness of this entity, more cases will be identified, leading to the accumulation of demographic, histopathological, and clinical data. E-PS-05-024 Bullous dermatitis artefacta secondary to aerosolized spray abuse in a child. Case report and review of histomorphological changes in factitious dermatitis K. Kamarádová*, L. Krbal, J. Bartoňová *Fingerland Department of Pathology University Hospital Hradec Králové, Czech Republic Background & objectives: Dermatitis artefacta is a psychocutaneous condition with self-inflicted skin injuries addressing a psychological need. The disorder is often underdiagnosed focusing on search for an underlying somatic cause. Even in cases with clinicopathological sus- picion the subsequent confirmation is often impossible. Methods: Here we report a case of 12-year-old girl with a confirmed diagnosis of cryothermic bullous dermatitis artefacta caused by an aerolised spray abuse. The patient was examined in our institution after a three-year history of bullous lesions appearing on various areas of the body. Results: Clinically, the lesions were nearly circular blisters filled with serous fluid, raising a suspicion of a bullous disease followed by a com- plex examination. Despite the initial treatment by prednisone the patient developed new lesions, some with progression to an ulcer or eschar. Punch biopsy was performed twice with negative direct immuno- fluorescence. First biopsy revealed lichenoid type of dermatitis with necrotic keratinocytes. Second biopsy contained a blister with necrotic epidermis with suspicion of bullous erythema multiforme. Persistent formation of lesions without any support for a somatic cause led to a suspicion of possible self-harm which was later admitted by the patient after repeated psychiatric evaluation. Conclusion: Although dermatitis artefacta is primarily a psychiatric disease, it can mimic true dermatosis and thus may be first seen by a dermatologist and possibly by a pathologist. Self-inflicted skin lesions have various mechanisms of injury upon which the histopathologi- cal picture is dependent often resulting in descriptive diagnosis. Main types of injury mechanisms and microscopic patterns are therefore reviewed emphasizing that dermatitis artefacta is a challenging diag- nosis, but it should be considered in uncommon cases of recurrent skin lesions. Funding: Supported by the project BBMRI-CZ LM2023033. E-PS-05-025 Malignant blue naevus as (undiscovered) primary site of recurrent melanoma metastases?: a case report L. Kovac*, G. Zamolo, T. Vučković, M. Belušić *KBC Rijeka, Croatia Background & objectives: Our aim is to present a case of a potentially malignant alteration of a blue naevus lesion and draw attention to the importance of researching this lesion, which, without proper diagnosis and therapy, can have life-threatening consequences. Methods: A 36 year-old male presented himself to a Clinic for Maxil- lofacial surgery with a sudden, painless swelling in the right preauricu- lar region, measuring 3x2 cm. A tumour mass in the right parotid gland was found. Cytology showed that it was a metastasis of melanoma. Superficial parotidectomy of the affected gland was indicated and then performed, with an orderly postoperative course. Results: Pathohistological analysis of the removed gland confirmed the diagnosis of metastatic melanoma. A search began for the primary melanoma site, which was never found. From the anamnesis, it was learned that the patient earlier underwent surgical excision of a mole on the right side of the temporal region. The pathohistological diagnosis of the excised mole showed that it was a benign blue naevus lesion. In the following years, the patient had regular controls and examina- tions which revealed multiple melanoma metastases throughout his body, for which he underwent more than 20 surgical procedures. The latest findings show two melanoma metastases that were found in the patient’s brain. Conclusion: Although the blue naevus lesion is a frequent diagnosis new findings point out the potential for malignant alteration, based on the increasing number of described cases. It is necessary to deepen the research on this potentially dangerous lesion, until it is determined when, in what way and if at all blue naevus can turn malignant, which will allow diagnostics and treatment to be reevaluated and performed more precisely, bettering the survival and quality of patients’ lives. E-PS-05-026 Fibro-osseous pseudotumour of the digit, arising in the distal pha- lanx of the thumb in a middle aged woman, a rare dermal and soft tissue tumour, a case report and review of literature F. Kubba*, S. Hughes, A. Owen *Department of Histopathology, Ealing Hospital, London North West University Healthcare NHS Trust, Middlesex, United Kingdom Background & objectives: A 56-year-old female presented with a slowly growing 13 mm ulcerated painful nodule on the pad of the right thumb, clinically thought to be a ruptured cyst It was locally excised. No recurrence was reported. No imaging was available. Methods: Microscopy showed a dermal tumour not connected to epi- dermis, expressing an irregular nodular growth pattern and composed of fascicles of variably cellular, spindle-shaped cells with minimal to mild cytological atypia, focally increased mitosis, dispersed in a pale myxoid stroma and focally reminiscent of nodular fasciitis. Widespread areas of cartilage, trabeculae of osteoid formation and osteoblastic rim- ming were seen. Results: Diagnosis: Fibro-osseous pseudotumour of the digit (FOPD). 21 cases were first described by Dupree et al in 1986; micro- scopically resembling myositis ossificans (MO) but lacking zon- ing. The presence of hypercellularity, mild cytological atypia and increased mitosis may be confused with parosteal or extraskeletal osteosarcoma.