ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 hypercellular glioma with brisk mitotic activity, palisading necrosis and microvascular proliferation. Case 2 was located in the parietal lobe and presented with seizures in a 10-year-old boy. The tumour was well-demarcated and displayed bizarre- looking giant cells and perivascular pseudorosettes. Mitotic figures were scarce but glomeruloid vessels were noted. Focal astroblastomatous features and abundant eosinophilic granular bodies were seen in both cases. Both patients underwent macroscopic resection and chemo-radiotherapy. In Case 1, the tumour recurred in 9 months, and the patient died 14 months after first admission. Case 2 is tumour-free after 23 months of follow-up. Conclusion: Neuroepithelial tumour, PATZ1-fusion is a molec- ularly defined provisional CNS tumour type which might be under-recognised due to its broad morphological spectrum and inconclusive immunoprofile. The biological behaviour of this tumour is yet poorly understood ranging from very aggressive clinical behaviour (Case 1) to more stable diseases with a risk of late recurrence (Case 2). E-PS-17-016 Confusing intracranial calcified lesion M.M. Hamzaoui*, A. Zehani, S. Bouali, B. Chelly, A. Ayari, O. Belhadj, I. Chelly, H. Azouz, K. Bellil, S. Haouet *Department of Pathology, La Rabta Hospital, Tunis, Tunisia Background & objectives: Calcifying pseudo neoplasm of the neu- raxis (CAPNON) is a rare, fibro-osseous lesion that can occur any- where in the central nervous system with 150 reported cases. It’s exclu- sively diagnosed by pathological examination. We describe a case of CAPNON mimicking an oligodendroglioma Methods: A 56 -year-old female presented with 2 years histor y of recur rent holocranial headache and dizziness which have worsened in the preceding month. Physical and neurological examinations revealed no obvious abnormalities. Magnetic resonance imaging (MRI) of the brain showed a complex calcified and cystic mass, measuring 40x32 mm in size, in the right frontal lobe. An oligodendroglioma was suspected. Results: Frontal craniotomy was performed and the entire mass was excised. Grossly, the 2.5-cm-sized lesion was a homogeneous, calcified mass without identifiable compartments. Histologically, the lesion consisted of glial tissue containing amorphous lamellar calcification with myxoid matrix in the background. The calcifications had concentric circular structure. In some places, osseous metaplasia was present. Around the lesion, peripheral palisading spindle to epithelioid cells was noted. Final diagnose is Calcifying pseudo neoplasm of the neuraxis. At follow up 1 year later, the patient was in a good condition and reported no discomfort. Conclusion: Calcifying pseudo neoplasm of the neuraxis is a rare, slow growing benign lesion that should be included in the differential diagnosis of intracranial calcified lesions to avoid improper treatment. This entity mimics many calcifying intra-axial lesions as ganglioglioma, oligodendroglioma, and infections like tuberculosis. E-PS-17-017 When the biomarkers decrease and the tumour increases: a case of intracranial growing teratoma syndrome F. Ramalhosa*, I. Luz, A. Carvalho, J.G. Soares, O. Rebelo *Serviço de Anatomia Patológica, Centro Hospitalar e Universi- tário de Coimbra, Portugal Background & objectives: Growing teratoma syndrome(GTS) is a rare clinical entity, which has been diagnosed in patients with intracranial germ cell tumour(GCT) who present a paradoxical enlarging of the original tumour despite the normalization of tumour markers during or after appropriate systemic chemotherapy. Methods: A 17-years-old male was admitted to Neurosurgery Depart- ment, after a diagnosis of an intracranial space-occupying lesion, made during the study of 5-month-long polydipsia and polyuria and diplopia. On MRI, the mass was well-demarcated, midline, involving the pineal area. Laboratory studies revealed elevated alpha-fetoprotein and beta- human chorionic gonadotropin, in the cerebral spinal fluid and blood. Ventriculoendoscopy and biopsy were performed. Results: The biopsy was a fragment of 0.5 cm that showed the presence of a germinoma, constituted by a poorly cohesive tumour of round medium-size cells, with positive immunostaining for C-Kit and OCT4. Three cycles of systemic chemotherapy were given (cisplatin, ifosfamide, etoposide). The tumour markers normalized, however the GCT had a volumetric enhance- ment. The patient underwent an occipital craniotomy for resection of the pineal tumour. Macroscopically, the tumour measured 3.0x2.0x1.5 cm and the histopathologic study revealed the presence of mature teratoma, com- posed of cysts lined by respiratory epithelium and mature neural tissue. Surprisingly, a foci of 0.3 cm of germinoma was found, with the same histological features described previously. Conclusion: The uncommon enlarging residual masses after treat- ment of intracranial GCT despite the concurrent normalization of tumour markers should warn for a possible GTS. GCT containing immature teratoma appears to be associated with a higher risk of developing GTS, once the chemotherapy induces the transforma- tion of immature cells into mature teratoma. E-PS-17-018 WHO 2021 histopathological grading of atypical and anaplastic meningiomas I. Guzelis*, F. Cakalagaoglu, I.E. Sevin, B.B. Yenen *Izmir Katip Celebi University, Turkey Background & objectives: As the WHO Central Nervous System was published in 2021, changes had been done in the grading of menin- giomas. In this study, we aimed to grade the atypical and anaplastic meningiomas and evaluate the prognostic value of histopathological parameters. Methods: Out of 316 patients diagnosed with meningioma, forty- three cases were diagnosed as atypical or anaplastic meningioma. All the slides of the cases were re-evaluated by a senior pathologist and a pathology resident for the grading parameters. Other than 4 patients that passed away perioperatively all the patients were followed up and the mean follow-up period was 42.8±33 months. Results: According to the new WHO grading system, 40 of the cases (95%) were graded as 2, and two cases were graded as 3. The special morphological meningioma subtypes were associated with spontaneous necrosis, higher mitosis, and the absence of prominent nucleoli (P=0.01, P=0.02, P=0.04). Small cells feature was associ- ated with mitosis criteria and no brain invasion (P=0.04, P=0.02). Spontaneous necrosis was correlated with higher mitosis (P=0.02). As no significance was found between histopathological grading parameters and recurrence-free (RFS) or overall survival (OS), in the subgroup of brain invasive meningiomas increased cellularity showed a better RFS (P=0.021). Spontaneous necrosis in brain invasive meningiomas worsened OS (P=0.049). Conclusion: In grade 2 and 3 meningiomas, as brain invasion and increased cellularity were the commonest and favourable findings, this study suggests that the spontaneous necrosis feature has an important prognostic significance in the brain invasive subgroup. While none of the histopathological parameters made a greater S318