ECP 2023 Abstracts

S326 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 E-PS-17-009 Spindle cell oncocytoma and granular cell tumour of the pituitary gland: report of three cases O. El Mnif*, F. Sassi, A. Zehani, A. Ayari, B. Chelly, H. Azzouz, I. Chelly, K. Bellil, S. Haouet *La Rabta pathology department Tunis, Tunisia Background & objectives: The 2021 WHO classification of the cen- tral nervous system’s tumour recognizes distinct low- grade neoplasm grade I of the sellar region:Pituicytomas, granular cell tumours (GCT) and spindle cell oncocytoma (SCO).We present 2 cases of SCOs and one case of GCT. Methods: Gross materials were fixed with 10% buffered formalin. Hematoxylin and eosin (H&E) sections of 4-5 microns were obtained. The cases (n=3) were analysed according to their histopathological, radiological and clinical features. S-100 protein and thyroid transcrip- tion factor 1 (TTF-1) were performed immunohistochemically. Two of the three cases were female and one male. The mean age was 53.6 years (range: 45-60). Results: Clinical findings at presentation included decreased visual acuity with left facial paralysis, headaches, and vertigo. Brain MRI showed an intra- and suprasellar expansive process with destruction of the dorsum sellae and floor, globular solid mass located in the supra- sellar region and a mass with enhancement in the sella. The three patients underwent resection. Grossly, the tumour was yellow and soft in two cases. Neuropathologi- cal analysis showed a proliferation of large ovoid and spindle cells in nests with abundant eosinophilic cytoplasmic granules with no mitosis and no necrosis. Immunohistochemistry in all cases showed positivity for S100 and thyroid transcription factor 1 (TTF-1). All the patients had no recurrence after total resection. Conclusion: SCO and GCT are rare tumours. These tumours manifest in patients aged 40 to 60 years and affect both genders equally. They can mimic adenoma, Rathke’s cleft cyst or present with endocrine dis- turbances. The best treatment is surgical removal. The primary obstacle to complete resection is the strong attachment of the tumour to nearby normal structures which necessitates adjuvant radiotherapy. E-PS-17-010 Immunohistochemical expression of MUC-4 in different subtypes of meningioma: descriptive study of all cases diagnosed in our hos- pital over a two-year period I. Fernández*, J.C. López, A. Tarín, J. Rosselló, L. Aguirrezabal, L. Ortega, S. Fernández *Hospital Universitario de Basurto, Bilbao, Spain Background & objectives: Meningiomas are the most common primary tumours of the central nervous system. However, current immunohistochemical markers for the diagnosis lack specificity and sensitivity. Several recent studies have proved that MUC-4, a mem- brane-associated mucin, is also expressed in these tumours. Methods: Immunohistochemistry with MUC-4 was performed in every meningioma diagnosed over two years (2021-2022) in the Pathology Department of our hospital, with a total of 44 cases. Afterwards, MUC-4 expression was evaluated, and positive staining was classified in three groups based on intensity and extension of the staining (diffuse, patchy or focal). Meningioma subtypes were also taken into account. Results: Most meningiomas (77%) showed positive MUC-4 expres- sion. Meningothelial meningioma was the most frequently diagnosed subtype, representing 80% of the cases; and most of them had a positive MUC-4 expression with either diffuse (34%), patchy (23%) or focal (20%) staining. All angiomatous, psammomatous and atypical men- ingiomas showed positive MUC-4 expression, with variable intensity and extension of the staining. However, fibrous meningiomas were MUC-4 negative in most cases (66%), with only one case showing focal positivity. Regarding clinical data, the age of the included patients was above 50 years in 82% of the cases; and both male and female population were similarly represented, being a 48% and 52% of the cases, respectively. Conclusion: This study shows that MUC-4 is frequently expressed in meningiomas, despite some differences in the staining pattern; with the exception of fibrous meningioma subtype, which is often MUC-4 negative. This suggests that this marker could be used in the diagnosis of meningiomas, but it might not be helpful in some cases. This study has some limitations because of the small number of cases. Nonethe- less, the results are concordant with the findings of other previous studies on this matter. E-PS-17-011 Morphological and immunophenotypic features of gliosarcoma M.J. Gil-Belmonte*, G. Urreta-Juárez, B. Agredano-Ávila, M.d.M. Berenguel-Ibáñez, F.J. Velasco-Albendea *UGC Anatomía Patológica, Hospital Universitario Torrecárdenas, Spain Background & objectives: The fifth edition of the WHO Classifica- tion for CNS Tumours gives IDH-wildtype glioblastoma its unique place among adult-type diffuse gliomas while recognizing its classical histological heterogeneity. This work aims to highlight the main mor- phological and immunophenotypic features of gliosarcoma. Methods: Two female patients in their seventies and eighties were diagnosed with a growing mass confined to the right and left temporal lobes, respectively. After surgical excision, well-defined elastic lesions were remitted for their analysis. Hematoxylin-eosin staining supported by immunohistochemical techniques for IDH-1, ATRX, p53, prolif- erative Ki67 index, vimentin, CK AE1/AE3, INI-1, and staining for reticular fibres were performed. Results: Hematoxylin-eosin sections showed, in both cases, a presum- ably glial-derived neoplasm with alternating areas exhibiting mesen- chymal differentiation. Tumours were composed of morphologically variable, atypical, and pleomorphic cellularity. Prominent microvascu- lar proliferation, increased mitotic activity, and extensive necrosis were observed. Immunohistochemical study revealed negativity for IDH-1 [R132H], retained ATRX, p53 heterogeneous positivity, and a high Ki67 (35%) index. GFAP stained positive in the glial component, while vimen- tin showed diffuse positivity for both glial and sarcomatous elements. Reticulin staining demonstrated dense bundles of reticular fibres in the sarcomatous regions. INI-1 evidenced a nuclear-retained staining pattern, while CK AE1/AE3 tested negative. An integrated diagnosis of glioblas- toma, IDH-wildtype, grade 4, gliosarcoma subtype was then released. Conclusion: Sarcomatous metaplasia can be found in some CNS neo- plasms, especially in the setting of de novo or recurrent glioblastoma IDH-wildtype. Gliosarcomas constitute a rare glioblastoma variant, accounting for 2% of glioblastomas. The demonstration of a dual mor- phological and immunohistochemical phenotype with biphasic glial and sarcomatous elements allows the designation of gliosarcoma, a distinct glioblastoma IDH-wildtype subtype. Thus, their histological and immunohistochemical peculiarities should be carefully regarded for an adequate differential diagnosis. E-PS-17-012 Isocytrate dehidrogenase 1 and 2 (IDH1and IDH2) mutations in brain gliomas – association with tumour grade and patients age D. Jasar*, K. Kubelka - Sabit, V. Filipovski, E. Stojkoska *Department of Histopathology and Cytology, Clinical Hospital Aciba- dem/Sistina, Skopje, Faculty od Medical Sciences, University “Goce Delcev” – Stip, North Macedonia Background & objectives: Isocytrate Dehidrogenase 1 and 2 (IDH1and IDH2) mutations are frequent findings in gliomas. The