ECP 2023 Abstracts

S288 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 (OSCC) (n:15) patients, and healthy individuals as control (n:15). The demographic data and clinical parameters of the patients were recorded. Determination of miR- 21 and PDCD4 expressions was done by using RT-qPCR and ELISA. Results: The results of the study showed higher miR-21 levels in both blood and saliva samples of OSCC patients compared to controls (p<0.05), while PDCD4 expression was lower in the OSCC group (p<0.05). In the oral dysplasia group, the miR-21 level was found to be higher than controls and PDCD4 expression was also lower (p<0.05). Conclusion: The PDCD4 and miR-21 displayed inverse expression sta- tus in both OSCC and oral dysplasia patients which may have potential as biomarkers in liquid biopsies. E-PS-12-023 An unusual case of neurofibromatosis 1 syndrome F. Gundogdu*, F. Soylemezoglu, Y. Atay, E. Eroglu, O. Kuscu *Hacettepe University Department of Pathology, Turkey Background & objectives: In neurofibromatosis 1 (NF1) syndrome neurofibromas and malignant peripheral nerve sheath tumours (MPST) are seen more commonly, unlike other unusual findings like hamar- tomas of the retinal pigment epithelium (RPE). Here, we present an unusual spectrum of NF1 syndrome. Methods: The clinical and pathological findings of the case were eval- uated. The 9-year-old patient had been following with the diagnosis of NF1 with multiple cafe-au-lait macules, neurofibromas, and pilocytic astrocytoma. Tumour excision and enucleation surgery were performed on the patient, who was found to have a giant mass extending to the right orbital area in the follow-up. Results: Macroscopically a 16 cm-sized, multinodular tumour was seen. Histologically, the tumour consisted of a major hypercellular spindle neoplasm showing marbled appearance, geographic necrosis, and increased mitosis adjacent to a multinodular, hypocellular, wavy spindle-cell neoplasm with interspersed collagen bundles. The hypocel- lular component was diffusely positive for S100 while the hypercel- lular tumour was only focally positive for S100 and showed loss of H3K27me2 expression. The diagnosis of MPNST arising from plexi- form neurofibroma was made. Macroscopic examination of enuclea- tion revealed a haemorrhagic globe. Microscopically, a hamartomatous lesion that was composed of disorganized glial tissue and proliferated RPE intermixed with prominent vasculature was seen. The diagnosis of combined hamartoma of RPE was made. Conclusion: NF1 is an autosomal dominant genetic syndrome that can be present with cutaneous and extracutaneous findings in various frequencies. Patients tend to have MPNSTs arising from neurofibromas at an early age. The combined hamartoma of RPE which is a benign lesion is one of the less common extracutaneous findings that can be a part of NF1 syndrome. E-PS-12-024 Laryngeal spindle cell squamous cell carcinoma: report of three cases S.E. Horoz*, I.T. Ceran, M.F. Tekin, O.C. Eren, N. Enver, L. Cinel *Marmara University, Department of Pathology, Turkey Background & objectives: Laryngeal spindle cell squamous cell carcinoma(SCSCC) is an epithelial malignancy that has undergone epithelial-mesenchymal transition. It is usually affecting elderly men. Less than 1% of all laryngeal malignancies is SCSCC. It is presented due to frequent misdiagnosis as sarcoma. Methods: One of three patient is woman. Ages of cases are 77, 77 and 88. One patient has a history of smoking and the other has radio- therapy. All of them present with variable durations of hoarseness. Laryngoscopy reveals polypoid masses located in the glottis in all cases. Excisional biopsy was performed in 2 cases, punch biopsy was performed in 1 case. Results: Histologically, in three cases, wide ulceration, focal dysplasia and in two cases squamous carcinoma in situ were observed in the surface epithelium. There was pleomorphic undifferentiated spindle cell proliferation in one case. In the other case, a nodular fasciitis-like histology was observed. The third case was resembled well differenti- ated leiomyosarcoma. Immunohistochemistry staining was observed as p40, p63 negative but SATB2 and p53 positive in all cases. PANCK was negative in two cases and focally positive in one case. In the leio- myosarcoma-like case, H-caldesmon and desmin were negative, while SMA was focally positive. With genetic analysis, USP6 translocation was not observed in the nodular fasciitis-like case. Conclusion: The diagnostic value of immunohistochemistry is lim- ited for SCSCC, especially in small biopsies. SATB2 may be helpful because 60 % of SCSCC is positive. In differential diagnosis, laryngeal sarcomas are often confused with SCSCC, but they are extremely rare and located deeper, not superficial mucosal lesions. The diagnosis of laryngeal SCSCC is based on the presence of a polypoid lesion with histologically undifferentiated spindle and/or pleomorphic cells and usu- ally associated with surface squamous dysplasia and/or invasive SCC. E-PS-12-025 A comparative study of the human dental tissue decalcification efficiency using various decalcifying agents P. Hurník*, V. Skopelidou, J. Stembirek, J. Vaculova, L. Izakovicova- Holla, A. Konecna, P. Porizka, M. Buchtova *University Hospital of Ostrava, Czech Republic Background & objectives: Decalcification is an important step in the processing of histopathological samples of hard tissues, particularly human teeth due to their high inorganic content. In this study, five different decalcification agents were evaluated for their effectiveness. Methods: During the study, 54 freshly extracted human teeth were processed. The following descaling agents were used: 5%nitric acid, 8%formic acid, decalcifier DC1, Microdecfast, and Lowy solution. The decalcified teeth were then routinely processed, sectioned, and stained. Corresponding samples were histologically evaluated (tissue morphology and staining characteristics). Furthermore, a spectrophotometric exami- nation of 4-6 randomly selected samples from each group was performed. Results: The study’s findings revealed that using 5% nitric acid resulted in the quickest decalcification of dental tissue. In this group, the shortest sample decalcification time was 19hours and the longest was 312hours. The microscopic histological quality of the prepared samples was also satisfactory. Using Lowy’s solution, on the other hand, resulted in the slowest decalcification. The process took a long time, and some teeth could not be processed properly in this solution even after two months of the study. Surprisingly, the results of the spectrophotometric analysis revealed that DC1 (combination of formic acid and formaldehyde) is the best decalcifying agent. The average decalcification time, however, was longer, averaging 20 weeks. Conclusion: High-quality preparation of human teeth samples is extremely difficult, as is determining the correct procedure and iden- tifying the best decalcification agent. It was found that 5% nitric acid appears to be the most effective decalcification agent (considering time and sample quality) for processing human dental tissue in routine histo- pathology practice. However, if time is not an issue, the most appropri- ate reagent according to the spectrophotometric examination is DC1, which ensures significant decalcification quality. Funding: This research was supported by the Ministry of Health (NU20-06-00189/2020) and by MH CZ—DRO (FNOs/2021) E-PS-12-026 p53 immunostaining can aid in accurate interpretation of p16 staining in the classification of head and neck squamous cell carcinomas J. Huvila*, P. Pakkanen, A. Silvoniemi, K. Aro, L. Bäck, H. Irjala, L. Aaltonen, J. Hagström, J. Laine, H. Minn