ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 membrane antigen, keratin 5/6, and negative for protein S100 and thyroglobulin. The diagnosis of PNPA was made. Conclusion: PNPA is a rare subtype of conventional nasopharyn- geal adenocarcinoma accounting for less than 0.48% of all malig- nant nasopharyngeal tumours. It is characterized by a papillary architecture and an unusual expression of TTF-1. Pathologists should be aware to distinguish it from thyroid papillary carci- noma due to morphological similarities. The negativity for thy- roglobulin supports the diagnosis of PNPA. E-PS-11-021 Human papillomavirus-related multiphenotypic sinonasal carcinoma: a report of three cases J.H. Nam*, Y. Choi *Department of pathology, Chonnam National University Medi- cal School, Republic of Korea Background & objectives: Human papillomavirus (HPV)-related multiphenotypic sinonasal carcinoma (HMSC) is an emerged tumour restricted to sinonasal tract. We will describe an unique feature of HMSC, discuss its distinction from other tumours, and draw attention to the uncommon HPV subtypes in given cases. Methods: We selected 3 HMSC cases diagnosed between 2015 and 2021 at our hospital. Immunohistochemical stains for p16, c-kit, p63, and SOX-10 were performed along with HPV DNA test using PANA RealTyper™ HPV Kit (PANAGENE Inc., South Korea). Results: All cases were from men aged 60 to 86 years (mean, 75), and all tumours were larger than 3cm in size (mean, 4cm). Histologically, solid nests of basaloid cells and cribriform pattern were the main characteristics. Every case demonstrated atypia of surface squamous epithelial layer, morphologically similar to the squamous cell carcinoma in situ. All 3 cases showed strong, dif- fuse positivity for p16, and it is noteworthy that positive results were also obtained in the surface squamous epithelial layer, including the lesion showing the atypical change. As a result of the HPV DNA test, all three cases had different high-risk HPV subtypes (18, 56, and 82, respectively). Conclusion: These results may suggest the possibility that the dominant HPV subtypes of HMSC in East Asia are different from those in the West. Still, an accurate interpretation is difficult due to the limited number of cases. E-PS-11-022 High-grade transformation of acinic cell carcinoma with amplification of HER2 gene C. Huang*, Y. Lee, M. Hsieh *National Taiwan University Hospital, Taiwan Background & objectives: Acinic cell carcinoma is a salivary gland carcinoma showing serous acinar differentiation. It is usually slow- growing with a 10-year survival of almost 90%. However, high-grade transformation has been rarely reported, and is associated with a significantly worse outcome. Methods: We reported a newly diagnosed acinic cell carcinoma with high-grade transformation in the parotid gland of a 64-year- old female. The clinical history, morphologic features and immunohistochemical profiles were described. HER2/neu gene amplification was analysed by fluorescence in situ hybridization (FISH). Results: Our case presented with a right parotid 3 cm-sized painful tumour with facial paresis for four months. She under- went total parotidectomy, and the histology revealed focal classic acinic cell carcinoma. High-grade transformation was identified, characterized by anaplastic cells with abun- dant cytoplasm and pleomorphic nuclei, arranged in irregular islands with comedonecrosis. Both the classic and high-grade components exhibited positive nuclear staining for NR4A3. The high-grade area showed stronger expression of cyclin D1 and p53, and had a higher Ki-67 index. These high-grade foci also demonstrated 2+ staining of HER-2/neu. FISH confirmed the HER-2 gene amplification in the high-grade component (HER2/CEP17: 2.13; HER2 copy number 5.5), but not in the conventional component. Conclusion: Prevalence of HER2 positivity in salivary gland carci- noma varied significantly between histological subtypes. Here, we described the first case of acinic cell carcinoma with HER2 gene amplification confirmed by FISH. The amplification detected in the high-grade foci but not in the conventional area further sug- gested the possible role of HER2 in the pathogenesis of high-grade transformation in acinic cell carcinoma. Recognizing this molecu- lar event is crucial because HER2 is an important potential target for therapies. E-PS-11-023 Desmoplastic small round cell tumour of parotid gland: a rare case report N. Chandran*, K. Sigamani *Karpaga Vinayaga Institute of Medical Sciences and Research Centre, India Background & objectives: Desmoplastic Small Round Cell Tumour (DSRCT) is an uncommon malignant mesenchymal tumour that affects mostly children and young adults with a striking male predilection and it commonly involves the soft tissue of abdomen and pelvis. Methods: Around 6% DSRCT”s have been reported in various extra- abdominal sites. Primary involvement of Parotid gland by DSRCT is extremely uncommon with only seven cases reported in literature. Here we present another case of DSRCT involving the parotid gland of a male patient. The detailed clinical, radiological and pathological find- ings of this case have been analysed and presented. Results: A 54 year old male presented with a swelling in right parotid region for 6 months duration. On examination, the swelling was 6x5 cm in size, hard and was lifting the ear lobe. CT neck revealed a right parotid mass. FNAC was inconclusive and thus right total parotidectomy was done. Grossly, the tumour was grey white with areas of necrosis. Microscopic examination showed salivary gland parenchyma with an adjacent malignant neoplasm composed of uniform small round cells with scant eosinophilic cytoplasm and regu- lar round nuclei arranged in nests separated by broad bands of desmoplastic fibrous stroma. IHC revealed S100, CKAE1/ AE3, desmin and synaptophysin positivity. Final diagnosis of DSRCT was made. Conclusion: DSRCT is considered as a tumour of uncertain his- togenesis. Extra-abdominal DSRCT involving the parotid gland should be differentiated from other primary salivary gland tumours and several small round blue cell tumours. The tumour shows poly- phenotypic differentiation expressing epithelial, mesenchymal and neuroendocrine markers in IHC studies. Molecular studies show characteristic translocation, t(11,22) with EWSR-WT1 gene fusion. Extra-abdominal DSRCT involving Parotid gland poses diagnos- tic challenge. Careful microscopic examination aided by IHC and molecular studies will help in diagnosing this uncommon mesen- chymal tumour. S285