ECP 2023 Abstracts

S183 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 pathologists should be aware to include it in the differential diagnosis of fibromyxoid tumours of acral sites. There has been no report of malig- nant transformation, however incompletely excised SAF has a tendency to recur. An early diagnosis, along with complete resection and follow up can prevent recurrence. E-PS-05-014 Prevalence and patterns of NTRK immunohistochemistry in Spitz lesions: a single-centre study C. Dahlstedt-Ferreira*, F. Nogueira, I. Leskiv, M. Dias, J. Nogueira, D. Gomes Pinto *Hospital Garcia de Orta, EPE, Portugal Background & objectives: Diagnosing melanocytic proliferations can be challenging, which is particularly true for Spitz lesions. Vari- ous genetic alterations have been described in these, namely NTRK- fusions. This study aims to describe the prevalence of NTRK immuno- histochemistry positivity and staining patterns in Spitz lesions. Methods: We collected 48 Spitz lesions from our institution over the past five years. All cases of histologically confirmed Spitz lesions were included. NTRK immunohistochemistry was performed using the VENTANA pan- TRK(EPR17341) assay, divided into positive (threshold of ≥1% stained cells) and negative. The study is ongoing, with molecular correlation and confirmation using the IdyllaTM-Gene Fusion Assay(Biocartis) planned for the next stage. Results: Our sample included 32 Spitz Nevi, 8 Reed Nevi, 3 AST, and 5 Spitzoid Melanomas. Five cases demonstrated pan-TRK positivity (1 Reed Nevi, 4 Spitz Nevi), with varying intensity and staining pattern. Cyto- plasmic and/or membrane staining were considered positive. No AST or Spitzoid Melanoma cases showed pan-TRK positivity. The observed prevalence of NTRK immunohistochemistry positivity is consistent with published literature for Spitz lesions, 2 of the Reed Nevi showed a weaker staining pattern, with an added difficulty due to the high deposition of melanin pigment, being considered negative on immunohistochemistry and waiting for molecular studies. Conclusion: Our study provides insight into the prevalence of NTRK immunohistochemistry positivity and staining patterns in Spitz lesions. This seems to be in line with the literature for more expensive molecu- lar tests, supporting the role of immunohistochemistry as a surrogate marker. We identified different staining patterns in different patholo- gies, which could be a path of future research. Validation in larger, multicenter cohorts is warranted to confirm our findings and refine diagnostic approaches for NTRK testing in Spitz lesions. E-PS-05-015 Subcutaneous and pulmonary nodules in a patient with systemic lupus erythematosus F. Dolkiras*, N. Stavrinou, P. Vlachou, A. Therapontos, C. Vourlakou *Evangelismos General Hospital, Pathology Department, Greece Background & objectives: A 75-year-old patient with a history of systemic lupus erythematosus presented with subcutaneous nodules in the left thigh. Upon imaging, bilateral pulmonary nodules were found. Biopsies were taken from both the lung and the subcutaneous nodules. Methods: Histopathological examination of the subcutaneous nodule revealed ischemic necrosis of the subcutaneous fat. Closer examination revealed an angiocentric processes with fibrinoid necrosis of the vessel wall. The infiltrate was transmural and polymorphous with occasional clusters of large cells. The nodule of the lung was completely necrotic with no viable cells. Results: The large cells were positive with various B cells markers and in situ hydrization for EBV associated RNAs (EBER) was positive. A differential diagnosis between EBV-positive DLBCL, NOS, lym- phomatoid granulomatosis grade 3, diffuse large B-cell lymphoma, lymphomatoid granulomatosis-type, EBV+ in the setting of immune deficiency/dysregulation (systemic lupus erythematosus under treat- ment with azathioprine) was raised. The EBV viral load was low, the systemic lupus erythematosus was managed with azathioprine which was halted 6 months prior to the presentation. Upon clinicopathologi- cal correlation the overall picture and the sites involved were more consistent with a diagnosis of lymphomatoid granulomatosis grade 3. Conclusion: Lymphomatoid granulomatosis is a rare disease easily overlooked by the clinicians and the pathologists and should be in the differential diagnosis of patients presenting with pulmonary-cutaneous nodules E-PS-05-016 Evaluating the diagnosis of mycosis fungoides: a uni-centre, multi- year approach D. Egong*, C. Brodie, H. Ingoldsby, A. Shalaby, S. Phelan *University of Galway, Ireland Background & objectives: The International Society for Cutaneous Lymphomas (ISCL) describes a set of criteria for diagnosing early mycosis fungoides (MF), which is not in routine use. This study evalu- ates the MF diagnostic reports in University Hospital Galway (UHG) against the ISCL criteria. Methods: Cases of cutaneous haematopoietic cell malignancies diag- nosed in UHG from January 2011 to December 2022 were retrieved from the electronic health record system using the search terms: ‘skin’, ‘lymphoma’, and ‘mycosis fungoides’. Clearly diagnosed MF cases were identified. The clinical, histopathological, molecular, and immu- nopathological features reported for these cases were compared against the ISCL diagnostic criteria and scored. Results: 19 of the 109 retrieved cases were reported as cutaneous T-cell lymphomas. 18 were classified as MF. One case was reported as lym- phomatoid papulosis; one of the MF cases was diagnosed as pagetoid reticulosis. These two reports were not scored. Within the twelve-year period, MF diagnosis ranged from 0 to 4 cases per year. 17 cases reported adequately on histopathological features, 14 on molecular, 9 on clinical and 7 on immunopathological features. Patients’ age at diagnosis ranged from 27 to 84 years old. The most frequently demonstrated T-cell recep- tor (TCR) gene rearrangements affect V-J1+2 and D-J domains in the TCRB chain, and V1+10-J and V9+11-J domains in the TCRG chain. Conclusion: The ISCL criteria is useful in aiding MF diagnosis. Our study reveals that clinical information, such as persistence of skin plaques and poikiloderma should be reported during specimen submis- sion. Immunopathological reporting of CD2, CD3, CD5, and CD7 posi- tivity should include an estimated percentage. Dermo-epidermal discord- ance of said markers should also be noted. The low number of MF cases diagnosed over a period of twelve years signals that a multi-centre study should be undertaken to better characterise MF patient epidemiology. E-PS-05-017 A strange debut: antiphospolipid syndrome with extensive cutane- ous necrosis and no systemic involvement G. Escuer*, P. Puente López, R. Escudero-Tornero, T.G. Sobral- Costas, E. Sendagorta-Cudós, J.M. Busto-Leis, E. Ruiz-Bravo, M.J. Beato-Merino *La Paz University Hospital, Spain Background & objectives: Antiphospolipid syndrome (APS) has a wide spectrum of skin manifestations from livedo reticularis to skin ulcers. Extensive cutaneous necrosis is rare but possible. We present a case with an unusual onset: extensive skin necrosis without systemic involvement. Methods: For this case report we searched the patient´s electronic medical records and analytics from his arrival at the emergency room as well as the medical history of a previous admission in another centre. For the literature review we searched Pubmed.