ECP 2023 Abstracts

S327 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 aim of this retrospective study was to determine association between IDH1/2 mutations and the glioma grade with the patients’ age. Methods: Samples from 184 brain glioma patients surgically treated in the period from January 2017 to December 2022 have been re-eval- uated. All the patients were histologically and immunohistochemically analysed to determine the type and grade of the tumour according the 2016 CNS WHO guidelines. The samples were further subdivided for IDH1 and IDH2 mutations according molecular analyses report. Results: No mutations were detected in grade I gliomas (n=13) while in grade II samples (n=31) mutations were observed in 14 cases (45%). Among grade III gliomas (n=58), mutations were found in 32 cases (55%) and in the group of grade IV gliomas only 7 cases were positive (8.5%). Patients with grade I and II gliomas were much younger (range 23-54, mean 39) compared with higher grade gliomas (range 49-72, mean 61, p<0.05). Conclusion: In our study group the majority of IDH1 and IDH2 mutant brain gliomas are more associated with higher tumour grade, possi- bly with tumour progression from grade II to grade III affecting older patients. E-PS-17-013 Change in macrophage subtypes ratio is a risk factor for intracra- nial aneurysm rupture: results of an extended study M. Koblizek*, M. Hundza Stratilova, A. Hejcl, A. Steklacova, V. Benes, J. Zamecnik *Department of Pathology and Molecular Medicine, 2nd Faculty of Medicine, Charles University, Motol University Hospital, Prague, Czech Republic Background & objectives: Prediction of intracranial aneurysm (IA) rupture is complicated as the underlying processes are not well under- stood. Our team previously presented importance of inflammatory infiltration in this process; however, further extension of studied cases was needed to get more robust data. Methods: Walls of both ruptured and unruptured intracranial aneu- rysms were neurosurgically resected, formol fixed and paraffin embed- ded. Each sample was routinely stained and immunohistochemical studies of CD45R0, HLA-DR and CD163 were performed to identify all leukocytes, M1 and M2 macrophages, respectively. Positive cells were counted in two hot-spots with area 0,314 mm2. Statistical signifi- cance was calculated using Mann-Whitney test. Results: Totally 56 IAs (ruptured n = 20, unruptured n = 36) from 55 individuals (38 females, 17 males) were collected. Morphological changes of the vessel wall such as fibrosis and destruction of elas- tic membranes were observed both in ruptured and unruptured IAs. Quantity of all inflammatory elements was significantly higher in the specimens of ruptured IAs (p < 0.001). The M2:M1 ratio was low in the unruptured aneurysms. The ruptured aneurysms showed increased M2:M1 ratio to > 1 and the difference between ratios in ruptured and unruptured IAs was statistically significant (p < 0.001). Conclusion: This study shows that there is significant increase in quan- tity of macrophages and increase of M2:M1 ratio in ruptured intrac- ranial aneurysms. We presume that these changes had to precede the rupture as the most of the patients with the aneurysm rupture were surgically treated shortly after clinical presentation. Funding: Supported by grant NU22-08-00124. E-PS-17-014 Primary central nervous system GFAP-negative pleomorphic tumour with histiocytic differentiation? O. Kuczkiewicz-Siemion*, M. Zdzienicki, P. Rutkowski, K. Seliga, A. Tysarowski, A. Szumera-Ciećkiewicz *Department of Pathology, Maria Sklodowska-Curie National Research Institute of Oncology Warsaw, Poland Background & objectives: The BRAF mutation is characteristic of specific subtypes of brain tumours as well as tumours of histiocytic origin. We describe a case of a 43-old male with a BRAF-positive brain tumour located in the lateral sulcus area. Methods: The tumour was under observation from October 2021, when the patient presented with an epileptic seizure. In January 2023, the patient was qualified for the tumour excision and sent for histo- pathological evaluation. The follow-up in March 2023 revealed tumour progression. Results: The histopathological examination showed a tumour composed of large pleomorphic epithelioid to rhabdoid cells with abundant eosin- ophilic cytoplasm, sometimes multinucleated, with scattered mitotic activity and focal necrosis. No microvascular proliferation was present. Additionally, the inflammatory and histiocytic background was promi- nent, with neutrophilic emperipolesis manifesting throughout the tumour area. By immunohistochemical evaluation the pleomorphic cells were: BRAF(+),S100(+),CD163(+),CD68(+/-)focally,GFAP(-),synaptophysin (-),IDH1R132H(-),olig2(-),ATRX(+),PR(-),EMA(-),ALK1(-),CD30 (-),CD15(-),CD3(-),CD20(-),CD23(-),CD117(-),MPO(-),Langerin(-), CD1a(-), SOX-10(-),HMB-45(-),MelanA(-),CD34(-),CKPan (-),SMA(-),desmin(-),MyoD1(-),Myogenin(-),Lysozym(-),EBER(IHS) (-),Ki-67(+)10%. The tumour exhibited an abundant underlying reticu- lin network, enclosing individual or small groups of neoplastic cells. The preliminary diagnosis of histiocytic sarcoma was established. The tumour tissue was sent for extended NGS analysis. Conclusion: The principal differential diagnosis included histiocytic sarcoma, pleomorphic xanthoastrocytoma and Rosai-Dorfman disease. However, none of the diagnostic criteria was fully met. The clinical course of the disease is relatively slow, and the mitotic index is low. Additionally, an interesting finding was neutrophils emperipolesis dem- onstrated throughout the tumour. E-PS-17-015 Alk-positive histiocytosis of the cavernous sinus and sellar region in an elderly woman M.E. Maracci*, L. Cardisciani, C. Ravaioli, E. Sabattini, M. Zoli, D. Mazzatenta, S. Asioli *School of Anatomic Pathology, Department of Biomedical and Neu- romotor Sciences, University of Bologna, Italy Background & objectives: alk-positive histiocytosis (ah) is a histio- cytic neoplasm first reported by chan jk et al. with multisystem or sin- gle-organ involvement and common favourable outcome. the histiocytic cells show mild cytologic atypia, positivity for histyocyte-associated markers, alk protein, and alk gene rearrangement. Methods: a 70-year-old female with a unremarkable personal history developed acromegalic features. in the suspicion of a somatotroph pit- net/adenoma she underwent mri that revealed a right cavernous sinus mass with infra-laterosellar extension, that was resected. Results: a diffuse cohesive polygonal cell proliferation with finely granular, mildly eosinophilic cytoplasm, without nuclear atypia was observed with scattered adenohypophyseal cells. mitoses and ki67- index were low. neoplastic cells showed positive cd68 and alk, patchy staining for s-100, negative cd1a, braf-v600e, gfap, ttf-1, pituitary transcription factors, gh, chromogranin-a, brachyury, cytokeratin cam 5.2. ini-1 was preserved. a diagnosis of alk-positive histiocytosis was rendered. Conclusion: we first report the case of a ah in the cavernous sinus in an elderly female with acromegalic features. The association of adenohy- pophyseal hypersecretion syndromes with ah has never been reported. Possible mechanisms explaining this association might be gh-hyper- secretion induced by histiocytic cells, induction of local prolifera- tive signals on the adjacent adenohypophyseal-neurosecretory cells or the presence of a metachronous pitnet/adenoma. in our case, no