ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 non-synonymous variants in tumour margins that were reported in the ClinVar database as “pathogenic”, “likely pathogenic” or “uncertain significance”, and were simultaneously not present in the peripheral blood, were selected for further analysis. Results: In total, we found 21 mutated genes, among them mainly tumour suppressor genes involved in DNA repair. We detected mutations in DNA isolated from 22/26 tumours, and in 5/26 tumour margins. Gene TP53 was the most commonly mutated gene fol- lowed by BRCA1/2 and CDKN2A. The median tumour load was 2 pathogenic mutation per patient on average (range 0-9). This parameter did not correlate with the presence of histological mark- ers like perineural invasion probably due to small cohort size. Sim- ilarly, we did not observe association of mutations in resection margins and probability of disease relapse. Conclusion: The spectrum of the tumour mutations is similar as in other studies with the exception of mutations in the BRCA genes, which were not found frequently mutated in OSCC (12-19%). The data in the literature suggests BRCA mutation in OSCC examined by imunohistochemistry technique ranges from 44% (139patients) to 63% (60patients). Variants identified in our dataset are often introducing stop codons leading to truncated and non-functional proteins. The potential application of BRCA(PARP) inhibitors for OSCC needs to be elucidated. PS-02-019 Keratinising pleomorphic adenoma of parotid salivary glands: analysis of three cases from practice M. Myroshnychenko*, I. Brodetskyi, V. Malanchuk, O. Dyadyk, Y. Kalashnyk-Vakulenko *Kharkiv National Medical University, Ukraine Background & objectives: Pleomorphic adenoma (РА) of parotid salivary glands (PSG) with squamous metaplasia, keratin cysts formation (keratinizing PA) is not common and causes difficulties in diagnosis. The objective was to analyse three cases from practice of keratinizing PA of parotid salivary glands. Methods: Surgical material from two women, one man with keratinizing PA was studied. The mean patients’ age was 36.3±2.1 years. In two cases, primary surgical treatment was performed, in one case – secondary, due to relapse. During examination it was noted in PSG a painless nodule of dense consistency in diameter from 1.5 to 4.5 cm. Histological, histochemical methods were used. Results: Macroscopically in three cases the nodes on the cut were of whitish-pinkish colour with cyst formation. Microscopically, the tumour was characterized by the predominance of the parenchymal (epithelial) component over the mesenchymal (stromal) one. The epithelial component was represented by epithelial, myoepithelial cells. Epithelial cells were of basaloid, spindle-cell, squamous, clear-cell type. They formed nests, strands with numerous foci of squamous metaplasia and keratinous cysts lined by squamous epithelium and containing eosinophilic keratin substance. The stroma was represented by connective tissue, vessels and myxoid, chondroid, osteoid, mucoid zones. In two cases, the tumour was surrounded by a distinct fibrous capsule with tumour invasion; in one case the capsule was absent. Conclusion: Morphological diagnosis of keratinizing PA causes certain difficulties for pathologists and requires a differential diag- nosis with mucoepidermoid carcinoma, necrotizing sialometapla- sia, squamous cell carcinoma. In the studied cases, morphological examination revealed a keratinizing PA of PSG with a predomi- nance of the epithelial component over the mesenchymal one. The presence the relapse in one case in anamnesis; tumour invasion into the capsule in two cases, absence the capsule in one case indicate that keratinizing PA is prone to recurrence. PS-02-022 Frequency of SDHx variants in middle ear paragangliomas V. Pavlov*, M. Fedorova, E. Pudova, D. Kalinin, A. Golovyuk, G. Krasnov, A. Kobelyatskaya, A. Snezhkina, A. Kudryavtseva *Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, Russia Background & objectives: Middle ear paragangliomas (MEPGLs) are rare neuroendocrine tumours occurring on the medial promon- tory wall of the middle ear. MEPGLs are highly hereditable, being susceptible to mutations in driver genes, such as SDHx coding for succinate dehydrogenase subunits. Methods: Total of 28 MEPGLs were subjected to genetic test- ing on the presence of SDHx variants using Sanger sequencing on an ABI PRISM 3500xL (Thermo Fisher Scientific) based on designed specific primers for all exons of target genes. Results: Four pathogenic mutations (4/28, 14%) were found among studied MEPGLs: missense and nonsense var iants in the SDHB gene, [NM_003000.3:c.689G>A (rs587782604) and NM_003000.3:c.79C>T (rs74315369)], respectively, as well as two missense mutations in the SDHD gene, [NM_003002.4:c.305A>G (rs104894302) and NM_003002.4:c.274G>С (rs80338845)]. This work was per- formed using the equipment of EIMB RAS “Genome” centre (http://www.eimb.ru/ru1/ckp/ccu_genome_c.php ). Conclusion: According to the literature on head and neck paragangliomas, SDHB variants are most frequent (33%), followed by SDHD variants (21%). This research showed low and close frequencies (7%) for variants both in SDHB and SDHD genes for Russian patients with MEPGLs. These results are similar to those for patients with MEPGL in other populations. Thus, development of MEPGLs may be linked with prevalence of mutations in other PGL susceptibility or cancer-associated genes. The study was funded by grant МК-5956.2021.1.4. PS-02-023 Sinonasal inverted papillomas with multiples recurrences: revision of our experience and HPV status L. López Vilaró*, M.C. Campos Marmol, J.R. Gras Cabrerizo, M. Casasayas Plass, S. Bagué Rosell, J. Szafranska *Department of Pathology. Hospital de la Santa Creu i de Sant Pau, Spain Background & objectives: Inverted Papilloma (IP) is a rare sinonasal tumour with local destructive potential and risk of malignant transformation. The aim of this study is to compare clinicopathologic features of a multirecurrent IP group and a none-multirecurrent IP group and its HPV status. Methods: We reviewed clinical and pathological data of patients diagnosed of IP during the period of 1978-2020 in our institu- tion and selected the recurrent cases. The IP group with more than one recurrence, treated by diverse surgical procedures, was compared with another group of IP with one recurrence. We per- formed p16 IHQ (Dako) study and HPV Genomic PCR. Results: The study included 152 patients from which 22 had recurrent IP.13 patients had multirecurrent IP,9 were males with a median age of 59, 11tumours were localized in ethmoid-sphe- noid sinuses. Four patients were smokers,2 had allergy and 2 had toxic exposures. Three IPs in the multirecurrent group showed low-grade dysplasia and one SCC.p16 was positive in 8cases, in 2 PCR showed presence of HPV, one determination negative and 10 not valuable. Nine patients presented with none-multirecurrent IP,8 were males with a median age of 56, 6 were localized in ethmoid-sphenoid sinuses. Five patients were smoker and 1 had toxic exposure. They had not dysplasia or SCC associated.p16 was positive in 3cases but PCR were not valuable. S74