ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Conclusion: Fusion of RREB1-MKL2 has been recently described in 90% of ectomesenchymal chondromyxoid tumour (ECMT), all located in the tongue, in a biphenotypic « oro- pharyngeal » sarcoma, a biphenotypic sinonasal sarcoma and two mesenchymal tumours involving the superior mediastinum. Our unusual case broadened the spectrum of mesenchymal tumours associated with RREB1-MKL2 fusion. Despite sharing some similarities with the phenotype of ECMT, whether our case rep- resents extra-glossal ECMT remains uncertain. E-PS-22-023 Immature teratoma of the thigh (mixed germ cell tumour). A case report E. Koniaris*, I. Nikolopoulos, E. Mortakis, M. Chamourgiotaki, G. Kafiri *Pathology department, General hospital of Athens "Hippokratio", Greece Background & objectives: Immature teratomas (I.T.), also known as mixed germ cell tumours, are mainly found in gonadal sites, e.g., testis. Extragonadal location site is rare (2-5%) and mostly found to arise in the sacrococcygeal location (50-70%), or the gonads (30-40%). Methods: A 67-year-old male patient, admitted to our hospital with a pro- gressively enlarging painless mid right thigh mass, with no other reported complaints. Examination revealed a compact firm elastic tumour measuring 4X4 cm, without erythema or tenderness. On imaging, a regular heterogeneous mass was noted, and it was decided to be excised, with wide surgical borders. Results: Macroscopically, we received a wide excised skin specimen with a whitish brownish in hue and of elastic firm in consistency neoplasm. Histologically, the tumour was mainly composed of immature neuroepithelial elements, with immature cartilage and other immature elements of ecto- and endodermic lineage. Immunohistochemical studies were performed with the following antibodies: S100, which highlighted the neural elements, CK 8/18, which revealed the epithelial elements, WT1 was negative, a-fetoprotein and OCT4, were found to be focally reactive, chromogranine and synaptophysin were also found to be focal, desmin was reported as negative and the mitotic index ki67 varied 20-50%. The tumour was totally excised and had pushing borders. Conclusion: I.T. in the soft tissue of the thigh is extremely rare with only a few similar cases reported, in this very unlikely location, which one can only explain as a disturbed migration of the primordial germ cells along the urogenital ridge, and hence undergoing a microenvironment related transformation. In our patient we suggested metastasis from a germ cell tumour of the testis, but further imaging examination (testicular US) didn’t reveal any gonadal association, or any other lesions elsewhere E-PS-22-024 Immunohistochemical marker VEGF in the diagnosis of peri- odontal diseases K. Kosov*, N. Zhuravleva, E. Guryanova, V. Diomidova *Chuvash State University by I.N.Ulianov, Russia Background & objectives: The purpose of the study was to determine the effect of a chronic inflammatory-destructive process in periodontal tissues on the expression of vascular endothelial growth factor (VEGF), on the process of angiogenesis in the connective tissue structures of the gums. Methods: The study group - 20 patients (age 20-36 years) burdened with chronic generalized periodontitis of mild/moderate severity. Biopsy material (pieces of gum) was obtained during closed curettage after tooth extraction for orthopaedic and orthodontic reasons. VEGF was detected by an indirect immunohistochemical method. Polyclonal rabit anti-VEGF antibodies (ThermoScientific, USA) were used as the first antibodies. Results: In patients with chronic generalized periodontitis, VEGF-immu- nopositive vessels were found in the lamina propria with strong and mod- erate reactions to VEGF. In the own plate of patients in the control group (patients with intact periodontium who applied for planned dental care), most of the studied pieces of gum contained vessels that were not stained when reacting to VEGF. Conclusion: Expression of the VEGF protein reaches lower levels in healthy connective tissue areas of the gums and increases in periodonti- tis. VEGF is involved in the initiation and progression of inflammation from gingivitis to periodontitis. This is due to the ability to stimulate vasodilation and angiogenesis in an inflammatory response. Vascular endothelial growth factor (VEGF) has mitogenic activity, regulates endothelial cell migration, vascular permeability, and induces the expression of anti-apoptotic proteins in these cells. E-PS-22-025 Pseudoanaplastic/symplastic giant cell tumour of bone: case report and review of the literature S. Moussa*, A. Baccouche, M. Krifa, A. Bdioui, W. Majdoub, S. Mestiri, S. Hmissa *Pathology Department, Sahloul University Hospital of Sousse, Tunisia Background & objectives: Giant cell tumour of bone (GCTB) is a locally aggressive primary bone neoplasm. Unusually, conventional GCTB displays marked nuclear atypia designated as pseudoanaplastic change mimicking primary sarcoma or sarcomatous transformation. We aim to analyse clinico-pathological aspects of this entity. Methods: We present a case of pseudoanaplastic GCTB in a 14-year old girl, without significant pathological history. This case was diagnosed in our institution in 2022. Results: Patient presented with a mass of the upper extremity of the humerus. Magnetic resonance imaging showed infiltrating haemorrhagic lesion measuring 16x12x11cm, suggesting a telangiectatic osteosarcoma. There were no distant localisations on computed-tomographic scan. Grossly, the specimen consisted of numerous loose haemorrhagic fragments of soft tissue and bone. Histological examination revealed areas of typical GCTB composed of uniformly distributed giant cells interspersed with mononuclear cells exhibiting moderate atypia. Other areas demonstrated scattered foci of cells displaying marked nuclear pleomorphism. Mitotic figures were numerous. Prominent haemorrhage and necrosis were seen in these areas. Positivity for H3G34 made the diagnosis of pseudoanaplastic GCTB. Patient was treated using curettage. Conclusion: Pseudoanaplastic GCTB is an uncommon variant of a conventional GCTB which can mimic primary sarcoma or sarcomatous transformation. Distinction from a sarcomatous lesion is made by a careful analysis of all factors suggestive of malignancy. E-PS-22-026 An unusual presacral mass: case report S. Moussa*, S. Mestiri, W. Majdoub, O. Belkacem, S. Frini, A. Bdioui, S. Hmissa *Pathology Department, Sahloul University Hospital of Sousse, Tunisia S342