ECP 2023 Abstracts

S291 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Among our cases, 23% expressed p16 (n=10) and 77% were p16 negative (n=33). No significant association was found between p16 positivity and the following parameters: age, sex, smoking, alcohol intoxication, tumour localization, tumour size, clinical tumour stage T, clinical lymph node stage, degree of differentiation and degree of keratinization. Conclusion: Our results confirm that we are one of the countries with a low rate of HPV infection and that alcohol and tobacco intoxication remains the primary risk factor for CEIOP in Tunisia. We recommend to systematically include the p16 status in our anatomo-pathological reports of OPSCC. E-PS-12-037 Mandibular chondrosarcoma: a report of four cases W. Majdoub*, K. Ben Lazreg, S. Mestiri, Z. Lajmi, O. Belkacem, D. Benletaifa, A. Bdioui, S. Hmissa *Pathology Department Sahloul Hospital, Tunisia Background & objectives: Chondrosarcoma is the second most com- mon primary malignant bone tumour, occurring in the pelvis and ribs in the 4th decade. The localization inface’s bones and more particularly the mandible is extremely rare. We report four cases of mandibular chondrosarcoma (MCHS). Methods: It’s a retrospective study of 4 patients diagnosed with MCHS, listed in the Cancer Registry of Center Tunisia during a period of 15 years between 2006 and 2021. These tumours were diagnosed on biopsy or on hemimandibulectomy specimen. Results: The mean age was 57 years with extremes of 25 and 83 years. There were two males and two females. Two cases were diagnosed on biopsy and two cases on a hemi-mandibulectomy specimen. For tumours diagnosed on surgical specimen, the tumour size was 4.5 and 6 cm. Grade I chondrosarcoma was diagnosed in one case, two cases were consistent with grade II, and one case was a mesenchymal chon- drosarcoma. Excision was complete in mesenchymal chondrosarcoma case and incomplete in patient with chondrosarcoma grade II. Conclusion: The most frequent locations of chondrosarcomas devel- oped in the head and neck are the larynx, the maxillary bone, and the nasal region. Mandibular localization is extremely rare. Preoperative diagnosis is difficult because of the rarity of the lesion and the non- specific symptoms. The most common histological type is conventional chondrosarcoma, most of them are grade I and II. Grade III is rarely described. The main prognostic factors are the quality of excision, the TNM stage and the grade. E-PS-12-038 Post-traumatic proliferative activity of the nasal epithelial cells under experimental injury and repair therapy conditions A. Malysheva*, O. Reshetnikova, I. Berest, O. Teleshova, E. Burgelo *Immanuel Kant Baltic Federal University, Russia Background & objectives: The morphological integrity of the nasal mucosa is the important protective barrier of the upper respiratory tract from exogenous airborne pathological agents. The research aimed to study the epithelial proliferative activity features after experimental nasal injury and repair therapy. Methods: Histological and immunohistochemical(Ki-67) studies of the rats’ nasal mucosa’ tissue samples in 160 cases of the post-traumatic experimental rhinitis were carried out. The proliferating epithelial cells were determined on the 2nd, 5th, 10th, 14th, 21st, 30th, 42nd, 60th day after injury under various repair therapy conditions. Eighty animals(G2) had the 0.25% sodium deoxyribonucleate solution added to the standard anti-inflammatory treatment(G1). Results: The proportion of proliferating cells on the second day of the experiment were not statistically significant in both groups. On the 10th day in group No. 2 there was an increase in the number of proliferating cells up to 6.9; 6.2/7.9% (G1-5.4; 5.2/5.8%; р ˃ 0.05). The maximum increase was recorded in G2 on days 14-21: 7.5; 7.2/7.9% versus 6.6; 6.4/7.3%; р ˃ 0.05 in G1. By the 30th day, a gradual decrease in the number of proliferating cells was noted, but a statistically significant difference in the groups persisted even by the 42nd day. By the 60th day, the number of proliferating cells in the experimental groups had no statistically significant differences (р ˃ 0.05). Conclusion: The recent COVID-19 pandemic has highlighted the need to study the dynamics of structural adaptation of the human respiratory system in response to pathogens. The analysis of the conducted studies showed an increase in the proliferative activity of the epithelial cells of the nasal mucosa during the experimental use of the reparant. The data obtained are discussed in terms of the dynamic interaction between the mechanisms of damage and restoration of the integrity of epithelial tissues. E-PS-12-039 Merkel cell carcinoma in maxillary sinus. Case report and litera- ture review J.S. Marrero Afonso*, I.J. Expósito Afonso, L. Martínez Blanco, K.M. Gallardo Rodríguez, S. Carrión Marrero, A.J. Nazco Deroy, F.A. García Machado *Spain Background & objectives: Merkel cell carcinoma (MCC) is a rare skin cancer with a tendency to affect regional lymph nodes. Because of nonspecific radiological findings, its wide differential diagnosis in head and neck area, rarity and clinicopathological characteristics could justify its presentation. Methods: A 72 years-old female non-smoker patient with metabolic syndrome and a treated MCC in 2016. She presented a mild oppres- sive holocraneal cephalea with nasal congestion. A CT (august 2022) revealed a 5 cm heterogeneous lesion centred in the left maxillary sinus with extension to bone and soft tissue, highly suspicious of a primary malignancy. Therefore, an incisional biopsy was planned. Results: Gross examination revealed multiple red-whitish tissue frag- ments with moderate consistency. Microscopically, it was formed by necro-haemorrhagic material and few groups of small round blue cells with scant cytoplasm and big nuclei with dispersed chromatin. An ini- tial panel of immunohistochemistry (IHQ) revealed positivity to CK20, chromogranin A and synaptophysin. Absence of other lesions in radio- logical images compelled to amplify IHQ panel: positivity to CKAE1/ AE3, CAM 5.2, CD56, SATB2 and negativity to S100, calretinin, EBV was demonstrated. A final diagnosis of Merkel cell carcinoma was made, the patient underwent systemic treatment with avelumab and a partial response to treatment was obtained. Conclusion: Although Merkel cell carcinoma is rare in non-cutane- ous head and neck area, correlation with clinical history is important. Furthermore, it should be taken into account in differential diagno- sis to exclude other mimickers: carcinomas such as neuroendocrine carcinoma (CK20+, EBV- and SATB2+), sinonasal undifferentiated carcinoma and squamous cell carcinoma, olfactory neuroblastoma, melanoma, sarcomas, lymphomas and others. E-PS-12-040 Acquired encephalocele mimicking a glomus tumour. Case report and literature review J.S. Marrero Afonso*, I.J. Expósito Afonso, L. Martínez Blanco *Spain Background & objectives: Encaphalocele is the result of the her- niation of brain tissue through an osseous defect. It is related to trau- matisms, previous surgery, congenital defects and complicated otitis media. Its rarity and clinicopathological characteristics could justify its presentation. Methods: We report a 57 years-old female non-smoker patient in follow-up because of mixed bilateral hipoacusia and repeated otitis