ECP 2023 Abstracts

S274 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 cases after treatment. To the best of our knowledge, there are no previ- ous reports on primary cerebral FL. E-PS-11-017 Splenic Epstein–Barr virus associated leiomyoma: histological and immunohistochemical analysis of a single case in a university hospital M. De Uribe Viloria*, I. Voinescu, G. Escuer, E.M. Fernandez, G. Olmedilla Arregui *La Paz University Hospital, Spain Background & objectives: Splenic Epstein–Barr Virus associated lei- omyoma (EBVAL) is a rare entity associated with immunodeficiency. It is frequently found in the liver, though it can affect any organ and can occur at different sites synchronously or metachronously. No metastasis have been reported. Methods: We reviewed our files from 2010 to April 2023 finding a sin- gle case of EBVAL. The diagnosis was achieved by using Hematoxilin- Eosine and immunohistochemical studies. We present the case of an 18 year old female with a history of renal transplant, presenting with two splenic masses found in a routine follow up. Results: With the clinical suspicion of Lymphoma, an splenectomy was performed. Both lesions showed intersecting fascicles of bland monotonous spindle cells with indistinct borders, eosinophilic cyto- plasm and elongated nucleus with tapered ends and without atypia. It showed positivity for SMA, calponin and EBER, and was negative for CD117, CD30, CD3, CD79a, CD21, CD23, oestrogen and pro- gesterone receptors. The expression of fumarate hydratase and INI1 was preserved. The proliferation index (Ki 67) was close to 3%. Some areas presented dystrophic calcification. No necrosis or mitosis were identified. Conclusion: EBVAL is an exceptionally rare entity and due to its rarity it may pose a diagnostic challenge. The oncogenesis of smooth mus- cle tumours in immunosuppressed patients remains to be elucidated, though Epstein Barr virus (EBV) infection seems to play a central role. It is important to report the presence of mitosis, necrosis and atypia, since EBV associated Smooth muscle tumours display a wide spec- trum of histologic differentiation from benign, borderline, to malignant morphologic features. E-PS-11-018 Erdheim Chester disease. Histological, immunohistochemical and molecular analysis of a single case in a universitary hospital M. De Uribe Viloria*, M.M. Petrino, E.M. Fernandez, G. Olmedilla Arregui *La Paz University Hospital, Spain Background & objectives: Erdheim-Chester disease (ECD) is rare form of non-Langerhans cells histiocytosis with multi-organ involve- ment. Activating mutations of the MAPK pathway are found in most patients, mainly the BRAFV600E activating mutation (>50%). We present a case diagnosed in our centre. Methods: We reviewed our files from 2010 to April 2023 and found just a single case of ECD. The diagnosis was achieved using routine staining, immunohistochemical and molecular studies. Age at diagno- sis, symptomatology and radiological studies were obtained from the clinical history. Results: A 55 year old male presented with vomiting, asthenia and oedema in the lower extremities. A CT scan revealed an irregular sym- metric infiltration of the bilateral perirenal and posterior pararenal spaces (hairy kidney sign) and mesentery, with concomitant involve- ment of the pericardium. Blastic endomedular lesions were identified in both iliac crests. A biopsy of the retroperitoneal infiltrate was taken. Pathological analysis revealed an inflammatory infiltrate formed by foamy histiocytes with immunoreactivity for CD68, Factor XIII, BRAF and CD163. ALK-6, s100, CD1a and Langerin/CD207 were negative. BRAFV600E was mutated in molecular studies. Marked clinical and radiological improvement was achieved after Vemurafenib treatment. Verrucous keratosis Vemurafenib related appeared later on. Conclusion: ECD is a rare, multisystem and idiopathic disorder. Acti- vating mutations of the MAPK and PI3KCA pathway have been related to ECD. Due to its clinical heterogeneity the diagnosis may be chal- lenging. It should be place in the list of differential diagnosis regarding retroperitoneal processes around major vascular structures, ureters, and perinephric space. This case report emphasizes the importance of cor- rectly diagnosing this entity and performing molecular studies since prognosis is widely improved with the use of novel targeted therapies. E-PS-11-019 Extracavitary primary effusion lymphoma (EC-PEL) of the central nervous system: an evolving entity with diagnostic difficulties O.C. Eren*, O.M. Akay, O. Dogan *Koç University Hospital, Department of Pathology, Turkey Background & objectives: With its rarity and unconventional pres- entation, extracavitary primary effusion lymphoma (EC-PEL) of the central nervous system (CNS) poses diagnostic difficulty for both clini- cians and pathologists. To increase awareness and discuss diagnostic approach, we present a case of EC-PEL of CNS. Methods: A 62-year-old HIV(+) HBV(+) male presented with recent- onset headache and difficulty speaking. He had a 10-year-history of Burkitt lymphoma in complete remission. MRI revealed multiple lesions in cerebral hemispheres and scans revealed no systemic involve- ment. Stereotactic biopsy revealed infiltrative cells with immunoblas- tic/paraimmunoblastic morphology. Paraffin blocks from prior biopsy suggesting Burkitt lymphoma were retrieved and both were evaluated morphologically and immunohistochemically. Results: Neoplastic cells were CD45(+), CD20/PAX5/CD79a(-), CD10/Bcl-6(-), CD38/138(+), MUM-1/EMA(+); suggesting terminal B-cell differentiation. CD30, ALK, CD3, CD2, Bcl-2, CD23, IgM/G/ D/A/κ/λ were all negative. Expression of c-myc was diffuse (90%) and strong, with high Ki67-index (90%). Cells were positive with EBER(+) HHV-8 LANA(+) and a diagnosis of EC-PEL was made. Re-evaluation of previous biopsy approved presence of CD20(+), Bcl-6(+), c-myc(+, >95%), EBER(+), HHV-8(-) neoplastic cells with high Ki67-index (>95%), confirming Burkitt lymphoma as the initial diagnosis. Conclusion: EC-PEL should be considered in an infiltration of EBV(+)/HHV-8(+) cells of high grade immunoblastic/paraimmuno- blastic morphology in immunocompromised individuals. Systemic screening should be done to exclude classic PEL (with cavitary involve- ment) and large B-cell lymphomas secondarily involving the CNS. With limited cases described in literature, EC-PEL necessitates fur- ther emphasis for both pathologists and clinicians. Appropriate initial diagnosis, ensuing molecular workup and further clinicopathologic follow-up may culminate in upcoming tumour classification systems generating a distinct approach for this entity with unique properties. E-PS-11-021 Primary cardiac lymphoma as a pathological expression of acute myocardial infarction M.J. Gálvez*, F. Leiva-Cepas, A. Sanz Zorrilla, J. Osuna Soto, S. Haro Yuste, I. Sánchez Ramírez *Hospital Universitario Reina Sofía, Spain Background & objectives: Cardiac involvement in disseminated lym- phomas is frequent: 25% in autopsy series, but primary or localized cardiac lymphoma is exceptional. Methods: We present the case of a man in the sixth decade of life without toxic habits or cardiovascular risk factors who attended the emergency department due to typical chest pain with EKG changes.