ECP 2023 Abstracts

S356 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 hyperchromatic and rejected to the periphery, small nucleoli and scant eosinophilic/clear cytoplasm. One mitosis per 1.7 mm² and no necro- sis were observed. The immunohistochemical profile demonstrated neoplastic cells with positivity for CAM5.2, CKAE1/AE3 and WT1 (nuclear), BAP1 (no loss of expression), SMARCA4 (no loss of expression). Negative markers: CK5/6, calretinine, D2-40, p40, CD5, PAX8, Claudin4 and SALL4. The NGS molecular study result was EWSR1(8)- ATF1(4) fusion gene. Conclusion: Pathologists should be aware that EWSR1/FUS-CREB family fusions could be present in malignant epithelioid neoplasms with predilection for mesothelial-lined cavities. Until now did not cor- respond to any known tumour category, suggesting a novel entity with distinctive microscopic features, despite of it can share morphological features with tumours harbouring EWSR1/FUS-CREB fusions like Angiomatoid Fibrous Histiocytoma (AFH) and Epithelioid mesothe- lioma (EM). Further research is needed to clarify if these tumours are part of a spectrum along with EWSR1 rearranged EM and/or AFH. E-PS-22-013 Sclerosing epithelioid fibrosarcoma (SEF) with YAP1/KMT2A rearrangement: case report and systematic review of the literature L. Dore*, M. Iuzzolino, L. Samà, L. Ruspi, L.M. Terracciano, A. Bonometti, F.C.M. Cananzi, S.L. Renne *Department of Biomedical Sciences, Humanitas University, Pieve Emanuele, Milan, Italy, Department of Pathology, IRCCS Humanitas Research Hospital, Rozzano, Milan, Italy Background & objectives: SEF is a rare sarcoma characterized by MUC4 positivity and EWSR1-CREB3L1 fusion. However, a subset lacks MUC4-expression and EWSR1-CREB3L1-rearrangement and is instead characterized by YAP1/KMT2A rearrangement. We here report a YAP1/KMT2A-rearranged-SEF case and perform a systematic review of the literature. Methods: We identified a MUC4 negative SEF and performed a Tar- geted RNAseq. Systematic review of the literature was performed using the PRISMA guidelines. We systematically searched the literature for molecularly confirmed YAP1/KMT2A rearranged SEF cases. We recorded the clinical data (sex, age, site, depth, follow-up), the histo- logical data (mitotic count, necrosis) and MUC4 positivity. Results: 4/51 identified publications met the inclusion/exclusion-criteria accounting for 33 cases. We reported the 34th. Median age was 43.5 (interquartile range, IQR: 31.25–55.50) years; 19/34 (56%) of cases were female. Median tumour size was 3.2 (IQR:2.5–6.12) cm; 11/19 (65%) had a deep location; lower limb was affected in 11/19 (58%) cases. Median mitotic count (/10HPF) was 5 (IQR:2–9); necrosis was present in 4/9 (44%) of cases; MUC4 was never expressed (in 19 tested-cases). Survival analysis showed for distant metastasis (12 cases, 5 events) a mean survival of 12 months (CI95%:11–NA); for overall survival (14 cases, 5 events) the median survival was 80 months (CI95%:24–NA). Conclusion: Less than 40 cases of YAP1/KMT2A-rearranged-SEF have been reported. Similarly to typical SEF, they arise in middle aged adults with equal sex distribution. They occur more often in the lower limb, not infrequently (35% of cases) in the subcutaneous fat. One out of three patients will die because of the disease. Recognition of these cases is therefore important for correct patient management. E-PS-22-014 Unusual presentation of Kaposi sarcoma: a case report of a lymph node localisation O. El Mnif*, A. Zehani, B. Chelly, A. Ayari, H. Azzouz, I. Chelly, K. Bellil, S. Haouet *La Rabta pathology department Tunis, Tunisia Background & objectives: Kaposi sarcoma is a malignant vascular tumour that occurs typically as a cutaneous or mucosal lesions related mostly to HIV infection However other locations may occur although rarely have been described. We report a lymph node location of Kaposi sarcoma. Methods: We analysed the medical file of a 47-year-old patient with a personal history of HIV infection who presented for about 6 months multiple cervical adenopathies, fluctuating fever and fatigue without any cutaneous lesions. Representative sections of the cervical mass were examined under H&E and immunohistochemical stains. Results: Initially the suspected diagnosis was lymphoma or lym- phatic tuberculosis in view of the endemic situation and medical history of the patient, a cervical adenomectomy was therefore per- formed the initial microscopic examination with routine hematoxylin and eosin staining was not at all suggestive of Kaposi’s sarcoma. It showed a lymph node parenchyma of globally preserved architecture containing lymphoid follicles with reactive germinal centres associ- ated with sinus dilatation. An immunohistochemical study was performed using the HHV8 anti- body showing an increased positivity of endothelial cells of the vascu- lar structures in the peri-ganglionic tissue, which concluded to a lymph node localization of a kaposi sarcoma. Conclusion: Lymph node localization of KS is a rare form of the disease that poses diagnostic challenges. It can mimic other tuberculous infection or malignant neoplasms, such as lymphoma. Therefore, a high index of suspicion for KS should be maintained in patients with HIV infection or other risk factors for KS who present with unusual nodal masses. E-PS-22-017 Solitary fibrous tumour of the spinal canal - a clinically challeng- ing case J. Ichikawa*, H. Imada, T. Kawasaki, M. Higashi *Department of Orthopedic Surgery, University of Yamanashi, Japan Background & objectives: Solitary fibrous tumour could occur almost anywhere, with the prototype being located in the pleura. Here, we report an unusual clinical course of spinal solitary fibrous tumour. Methods: A 55-year-old man complained of pain in his right back and the side of chest four years ago. An MRI revealed a spinal tumour at T6-7 and he was referred to our hospital. The back pain improved but four years later, he started to develop weakness in his left leg, which gradually spread to both legs, resulting in difficulty walking. Results: An MRI showed that the T6-7 tumour had grown. It was clini- cally suspected of meningioma and surgical removal of fragmented pieces of the tumour. The histological examination revealed that the tumour was composed of uniformly spindle-shaped tumour cells with haphazard distribution and occasional ectatic vessels. Differential diag- nosis of meningioma, Schwannoma and solitary fibrous tumour was suggested. Immunohistochemically the tumour cells were positive for CD34 and STAT6 while negative for S100 protein. These findings were consistent with solitary fibrous tumour. His symptoms were relieved after surgery and no recurrence has been confirmed to date. Conclusion: While solitary fibrous tumours can occur in various loca- tions, they are rare in the spinal canal. Pathological findings are rather straightforward, but clinical and radiological findings are challenging to diagnose. Our case will expand the knowledge about the clinical presentation of spinal solitary fibrous tumour. E-PS-22-018 Vertebral ochronosis - a rare, histologically confirmed case J. Ichikawa*, H. Imada, T. Kawasaki, M. Higashi *Department of Orthopedic Surgery, University of Yamanashi, Japan Background & objectives: Vertebral ochronosis is a rare disease com- monly associated with alkaptonuria and it is not common to have a chance of histological evaluation. Herein we report a case of vertebral ochronosis verified histologically.