ECP 2023 Abstracts

S328 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 neuroendocrine cell proliferation was detected, so we might primarily suppose that alk positive histyocytes induced gh-hypersecretion. E-PS-17-016 Primary melanoma of the brain: a case report of an extremely rare tumour I. Provatas*, P. Pantoula, E. Ventouri, D. Glarelis, M. Karagianni *Pathology Laboratory, General Hospital of Nikaia - Piraeus "Ag. Panteleimon", Greece Background & objectives: Melanoma of the brain is an extremely rare neoplasm, with most cases reported in the fourth and fifth decade. It has predilection for spinal cord or posterior fossa and it may appear with cord compression symptoms or mass effects. Methods: We report case of a 51 year-old female, with mass effect and without history of cutaneous, ophthalmic or mucosal melanocytic lesions, who was operated for a tumour located in the brainstem. Multi- ple segments of a dark brown, solid, elastic and partially friable tumour were received, 4 cm in maximum diameter. Results: On microscopic examination, the tumour segments consisted of compact aggregations and nests of homogenous, epithelioid or spin- dle-shaped cells, with high nuclear atypia, eosinophilic and focally amphiphilic or clear cytoplasm, with medium-sized vesicular nuclei and apparent nucleoli, in a relatively sclerotic stroma. 14 mitoses / 10 HPF were counted and there were focal extracellular melanin deposi- tions, many melanophage aggregations and extended necroses. The immunohistochemical control of the neoplasm revealed strong expres- sion of S-100, HMB-45, MART-1 and negativity for EMA, GFAP, CKAE1/AE3. Cell proliferation rate was very high, ~ 85%. Conclusion: Melanocytes are found normally in small numbers in the leptomeninges, but they are most frequently met over the anterior / lateral cord, brainstem, base of brain. They may give rise to rare pri- mary central nerve system melanocytic tumours, such as diffuse mel- anocytosis, melanocytoma and malignant melanoma. The diagnosis of primary melanoma is challenging, because of the morphological simi- larities with metastatic melanoma. In this occasion, it very important to exclude clinically other primary sites, especially skin, eyes or mucosae. E-PS-17-017 Myeloid sarcoma of the brain and spinal cord: three case reports S. Yilmaz Erozbek*, N. Yeldir, A. Çakır *Department of Pathology, Istanbul Medipol University, Turkey Background & objectives: Myeloid sarcoma (MS) is an extramedul- lary mass composed of myeloblasts, can occur at any age, can develop in skin, lymph nodes, bone-soft tissue, gastrointestinal tract but central nervous system is rare. Patients have concurrent or existing myeloid neoplasia.MS sometimes develops de-novo. Methods: We present 3 cases of myeloid sarcoma located in the central nervous system (two spinal, one brain). Results: Two patients were female. The ages of the patients were 3, 7 and 65 years. One patient had Down syndrome and was diagnosed with acute myeloid leukaemia (AML) and her mass was paraventricu- lar. The masses in the other two regions were cervical and thoracic extradural localized. Histopathological, blastoid cells with prominent nucleolus and high mitotic activity was observed. Although the blastoid cell morphology varied from case to case, immature, monocytoid and plasmacytoid appearance were noted. Immunohistochemical expression differed in each tumour; CD33, MPO, CD34, CD117, CD68, lysozyme, CD45 positivity were observed. FLT-3 mutated AML was detected in the bone marrow of the case whose mass was in cervical spinal. Conclusion: MS are masses formed by myeloblasts with different morphological features. It shows abnormalities in cytogenetics and complications like AML. Although the differential diagnosis var- ies according to its localization, it includes carcinoma, melanoma, lymphomas, plasmacytoid dendritic cell sarcoma, histiocytic sarcoma. These tumours especially kept in mind in de-novo MS. It should not be forgotten that MS can be seen in any localization at any age, and patients should be investigated for myeloid neoplasms. E-PS-17-018 Proposed to consider so called “low-grade astrocytoma, IDH- wildtype” as a tumour with a similar prognosis to glioblastoma, IDH-wildtype – Providing more simplified guidance for treatment to clinical departments C. Yoo*, U. Cho, S.H. Yang *The Catholic University of Korea, St. Vincent Hospital, Republic of Korea Background & objectives: Glioma, IDH-mutant is a completely dif- ferent disease from glioma, IDH-wildtype. Therefore, it was assumed that “low-grade astrocytoma, IDH-wildtype (LAIDHW)” is more like a glioblastoma, IDH-wildtype (GBIDHW). In this study, we looked at whether LAIDHW showed a similar prognosis to GBIDHW. Methods: We collected 85 cases of adult gliomas diagnosed from 2000 to 2018 in this institute. We reclassified the study cases according to the 2020 WHO. We were going to see how much LAIDHW was among them, and analysed whether there was a difference in survival time between low grade (grade 2) astrocytoma, IDH-mutant (LAIDHM), LAIDHW and GBIDHW using Log-Rank test. Results: Among them were 47 (55.3%) cases GBIDHW and 25 (29.4%) cases astrocytoma, IDH-mutant including 14 (16.5%), 5 (5.8%) and 6 (7.1%) cases of grade 2, 3 and 4, respectively. Cases included in this group were previously diagnosed IDH-mutant anaplastic astro- cytoma and glioblastoma. The other 13 (15.3%) cases were identified as LAIDHW. Therefore, it can be seen that LAIDHW which presents diagnostic difficulties accounts for a considerable amount. There were definite survival differences between LAIDHM and GBIDHW (p=0.01) as is well known. The survival curve between LAIDHM and LAIDHW showed a tendency to differ in survival but statistically insignificant (p=0.15). The survival difference between LAIDHW and GBIDHW was not found (p=0.42). Conclusion: We expected to see the survival difference between LAIDHW and LAIDHM. Unfortunately, there was no statistical sig- nificance, just a trend. The low number of cases is thought to be the reason for the weak statistics. It was difficult to see that there was a difference in survival period between LAIDHW and GBIDHW. We think statistical evidence will emerge as we add to the number of cases in the future, and we can safely include LAIDHW into the group of GBIDHW. E-PS-18 | E-Posters Ophthalmic Pathology E-PS-18-001 Primary CNS lymphoma – ocular variant: clinical and pathological features and treatment outcomes H. Fadlelseed*, M. Rhatigan, M. Treacy, C. Murphy, S. Kennedy, D. Kilmartin *Department of Pathology, St Vincent’s University Hospital, Dublin, Ireland Background & objectives: Ocular lymphoma is a subtype of primary CNS lymphoma (PCNSL). Cytological analysis of vitreous fluid is the gold standard in diagnosis. MYD88 L265p mutation and IL10: IL6 >1 are useful tools for diagnosis. Chemotherapy is the mainstay of treatment. Methods: Retrospective review of medical records and pathology specimens of 169 patients with suspected ocular lymphoma over an 11-year period in a tertiary hospital was carried out. Clinical