ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Background & objectives: Among tumours of the CNS, a combina- tion of glioblastoma and a primitive neurodermal tumour in young people is extremely rare. Intravital diagnosis of this type of tumour is difficult due to the difference in clinical and morphological picture. Methods: We present a case of a 38-year-old male with an intravi- tal diagnosis of glioblastoma associated with a primitive neuroe- ctodermal tumour of the brain. Due to the dimorphic structure of the tumour, the diagnosis was difficult, confirmed by histological and immunohistochemical studies at two independent hospitals. Despite treatment, the patient died. An autopsy with histological and immunohistochemical examinations was performed. Results: An autopsy revealed flabby brain tissue in the focus of the removed tumour of the frontal lobe of the right hemisphere of the brain, as well as multiple metastases in the pia mater and cerebellum. The subependymal and paraventricular regions (including basal nuclei) was affected as well. There was also an oedematous pia mater of the spinal cord with a total lesion with massive compression of the spinal nerves. Histologic examination of tumours showed high cellularity with a perivascular arrangement of polymorphic cells. The tumour has many vessels of various calibers, proliferation of thin-walled ves- sels, areas of necrosis. There are more differentiated areas resem- bling multiforme glioblastoma in structure. Conclusion: This case reminds us that in the presence of clear clinical symptoms of one type of tumour, a mixed type of tumour of central nervous system should not be excluded, which may affect therapy. E-PS-17-013 FET-CREB fusion positive intracranial mesenchymal tumour: a case report H.G. Terzioglu*, F. Soylemezoglu, B. Babaoglu *Hacettepe University, Turkey Background & objectives: Intracranial mesenchymal tumour with FET-CREB fusion, a provisional entity in the 2021 WHO blue book, is defined by gene fusions of the FET family of RNA binding proteins (EWSR1/FUS) to the CREB family of transcription factors (CREB1/ CREM/ATF1). Methods: We present a 24-year-old male patient, who presented with headache, dizziness and dysarthria. MRI revealed cerebral oedema and 23 mm sized, contrast enhanced mass in the right parieto-occipital region. Patient underwent craniotomy and total excision of the mass was done. Tumour was diagnosed as angio- matoid meningioma in another centre and brought our institution for a second opinion. Results: On morphological assessment, tumour had a myxoid and oedematous stroma with vascular structures having hemangio- pericytic pattern and focal chicken-wire appearance. Neoplastic cells have elongated nuclei with vesicular chromatin pattern and spindle shaped cytoplasm. Cytological atypia and necrosis were absent. Mitosis was counted as 2/10 HPF. Immunohistochemically, tumour cells were diffusely positive with EMA, desmin, GLUT1 and focally positive with CD99; while negative with GFAP, STAT6, MUC4, CD34, synaptophysin and S100. Fluorescence in-situ hybridization was performed, revealing EWSR1 rearrangement. These findings suggested the diagnosis of intracranial mesenchy- mal tumour, FET-CREB fusion positive. Conclusion: Here we presented EWSR1 rearranged, intracranial myxoid mesenchymal tumour, compatible with this diagnosis. Intracranial mesenchymal tumours with FET-CREB fusions, previously described as intracranial angiomatoid fibrous histiocytoma and intracranial myxoid mesenchymal tumour (IMMT), are a newly described group of tumours and mostly seen in paediatric patients and young adults. They are characterized by fusion of a FET family gene (EWSR1/FUS) to the CREB family of transcription factors (CREB1/CREM/ATF1). Clinical course, morphological features and genomic landscape is still unclear. E-PS-17-014 Brain metastasis of exceptional origin: retrospective study in a single institution M. Mellouli*, S. Graja, F. Kolsi, S. Makni, C. Kammoun, C. Chaari, S. Charfi, T. Boudawara, R. Kallel *Department of Pathology, Habib Bourguiba University Hospital, Sfax, Tunisia Background & objectives: The most common primary tumours of brain metastasis (BM) are lung cancer, breast cancer, melanoma, colorectal and renal cancer. BM of exceptional origin (BMEO) are poorly documented. In this study, we aim to report our experience about BMEO. Methods: We performed a retrospective study of BM diagnosed at our department over a period of 10 years (January 2010-December 2019). BM of pulmonary, colonic, mammary, renal and melanic origin were excluded. At all, 27 cases of BMEO were included in our study. Results: The median age of patients was 54 years. The study included 21 men and 8 women. Lesions were solitary in 15 cases and multiple in 12 cases. Tumours were located in the supratento- rial region in 13 cases. A history of a previously known cancer was found in 25 cases. Eleven patients underwent surgical resec- tion. The most common primary sites of BM were thyroid and prostate (four cases each), followed by bladder, ovary and bone (Three cases each) and testis and buccal mucosa (Two cases each). The other primary sites were oesophagus, pancreas, upper urinary tract urothelial, mediastinum, adrenal gland and palatine tonsil (one case each). Conclusion: Despite advances in imaging methods, there are no pathognomonic features that distinguish BM from primary malig- nant brain tumours or nonneoplastic conditions. Therefore the standard of diagnosis of BM remains pathological examination. Immunohistochemical and molecular analysis are helpful to make appropriate diagnosis. Correlation of histological findings with clinical and imaging results is necessary. E-PS-17-015 Two cases of MN1-PATZ1 rearranged neuroepithelial tumours with different histopathological and clinical features A. Afshari-Mehr, S. Nevis, L. Bhaw, R. Laxton, B. Clark, B. Zebian, J.P. Lavrador, F. Vergani, R. Bhangoo, F. Carceller, S. Al-Sarraj, I. Bodi, Z. Reisz* *Clinical Neuropathology, King’s College Hospital, United Kingdom Background & objectives: PATZ1-fusion is a rare molecular event among central nervous system neoplasms, which have recently been reported in a subset of glial/glioneuronal tumours mainly affecting young patients. Hereby, we present two cases of MN1-PATZ1 rearranged neuroepithelial tumours with different clinicopathological characteristics. Methods: A retrospective departmental study investigating 931 paediatric and young adult neuroepithelial tumours identified two previously unclassified gliomas harbouring MN1-PATZ1 fusion, confirmed by multimodal panel and methylation profil- ing (DKFZ, Brain tumour methylation classifier v12.5). Results: A 24-year-old woman (Case 1) presented with a contrast-enhancing left frontal mass. Histology showed a S317