ECP 2023 Abstracts

S290 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Conclusion: This low-grade malignancy is characterised by neoplastic gland formation with monomorphic lesional cells displaying clear to eosinophilic cytoplasm. The histological features of RCLSA are not specific to this entity, thus, one is required to exclude primary and metastatic tumours which have a similar morphology. Surgical resec- tion is the treatment of choice. The overall prognosis is favourable, with low recurrence rate and no reported metastasis. This is the first case to report the immunohistochemical results of CD56 and TFE3. E-PS-12-032 Head and neck follicular dendritic cell sarcoma - report of five cases A. Lakshmanan*, A. Subramanyam *Apollo Hospitals, India Background & objectives: Follicular dendritic cells (FDC) are acces- sory cells which play a major role in antigen presentation. FDC sar- comas (FDCS) are very rare and have been in reported in many sites. FDCS is often misdiagnosed due to lack of awareness about this entity. Methods: We retrieved cases of follicular dendritic cell sarcoma reported in the head and neck region for a period of 10 years and reviewed. Haematoxylin and eosin-stained sections and immunostains were reviewed and analysed. Clinical data were obtained from elec- tronic medical records. Results: We had 5 cases of follicular dendritic cell sarcomas arising in the head and neck region. Three were nodal and two cases were extra nodal in location. The patients age ranged from 34 – 46 years. There were 3 males and 2 females. Two cases had multiple recurrences. Sur- gery was the main stay of treatment with three of them received adju- vant chemotherapy and radiotherapy. They showed varied morphology with spindle, epithelioid and pleomorphic appearances. Conclusion: FDCS are rare neoplasms with intermediate prognosis. They have varied histomorphological patterns and are often misdiag- nosed, as four cases in our series were initially misdiagnosed as different neoplasms. Hence, awareness about these rare neoplasms and including them as a differential under neoplasms with spindled, epithelioid, and pleomorphic morphology would prevent misdiagnosing these entities. E-PS-12-033 An unusual site for extramedullary (extraosseous) plasmacytoma: nasopharynx - case report D. Lazureanu*, M. Cornianu, A. Jurescu, R. Cornea, A. Vaduva, A. Dema *University of Medicine and Pharmacy Victor Babes Timisoara, Romania Background & objectives: As specialists in head and neck pathol- ogy are aware, the incidence of nasopharyngeal plasmocytoma has a wide range, from 1% to 16% accordingly to different references. By all means its rarity uncover some challenges for histopathological diag- nosis to be accurate. Methods: The biopsy from a left-sided nasopharyngeal tumour mass of a 69 years-old male was routinely processed, paraffin-embedded and H&E stained. Ancillary test were needed: immunohistochemistry using a panel of antibodies (EMA, light chains, LCA, S100, CKs, synapto- physin, S100) in conjunction with imagistic investigation. Results: Endoscopic examination, magnetic resonance imaging (MRI) and tomography show a cauliflower mass (19 mm maximum diameter) starting from the nasopharynx and reaching the inferior left choanal process, without a cleavage plan. As a result of biopsy, the mass was characterized by high cellular density with eosinophilic cytoplasm and an eccentric nucleus. Neoplastic cells were positive for EMA and Kappa light chain, negative for all the rest. Also magnetic resonance imaging and computed-tomography excluded any other lesions or multiple myeloma-related tissue organ damage. Conclusion: Although nasopharyngeal plasmacytomas are rare, their histopathological recognition and the assurance through interdisciplinary consultations that the monoclonal proliferation of plasma cells is only with this localization, allows the optimal therapeutic conduct: radiotherapy. E-PS-12-035 Sino-nasal tract adenoid cystic carcinoma: a clinico-pathological study of 21 cases A. Maaoui*, I. Mallek, S. Kamoun, N. Ben Othmen, Y. Houcine, K. Hamza, S. Elfekih, I. Bettaieb, A. Goucha, Y. Chaabene, S. Ferchi- chi, N. Aloui, A. Methnani, S. Dhambri, M. Driss *Pathology Department, Salah Azaiez Institute, Tunis, Tunisia Background & objectives: Adenoid cystic carcinoma (ACC) is the second most common malignancy and the most common salivary gland- type tumour of the sinonasal tract. The aim of this study is to describe the clinico-pathological features of ACC series in Tunisian patients. Methods: A retrospective and descriptive study of 21 patients with ACC of sinonasal tract from 2003 to 2022, retrieved from the files of Pathology department of Salah Azaiez Institute. We reviewed the patients’ demographics (gender, age), the anatomic site, growth pattern, pleomorphism; bone, neural and lymphovascular invasion. Results: Twenty-one cases of ACC included 12 females and 9 males aged 28-84 years (mean 59,5). The tumours involved nasal cavity in 6 cases, the maxillary sinus in 14 cases and a combination of nasal cavity and paranasal sinuses in 1 case. Histologically, the tumour was composed of a variable growth pattern; predominantly cribriform (n=8), solid (n=2), tubular (n=2) and a combination of patterns in 9 cases. Pleomorphism was mild in most cases (n=11), moderate (n=7) and sever (n=3). These tumours showed bone invasion in 6 patients and neural invasion in 5 cases. Only one case of lymphovascular invasion was seen. Conclusion: ACC, while rare, represent the most common carcinoma of sinonasal tract. The diagnosis is essentially made on H&E stained slide. It is crucial to differentiate the ACC from the multiphenotypic sinonasal carcinoma, as the clinical features and management are dis- tinctive. The immunohistochemistry of p16 followed by high-risk HPV testing may help in the differential diagnosis. E-PS-12-036 Oropharyngeal squamous cell carcinoma: prevalence of Human papillomavirus infection A. Maaoui*, S. Kamoun, Y. Houcine, K. Hamza, N. Ben Othmen, S. Elfekih, I. Bettaieb, A. Goucha, S. Mhalli, F. Ammous, C. Hmaied, M. Dhaha, S. Kedous, M. Driss *Pathology Department, Salah Azaiez Institute, Tunis, Tunisia Background & objectives: Human papillomavirus (HPV) infection represents a risk factor for oropharyngeal squamous cell carcinoma (OPSCC). We aim to evaluate the prevalence of HPV infection in OPSCC by immunohistochemical study of p16 and the association between HPV status, epidemiological and anatomical-clinical factors. Methods: We conducted a retrospective study of 43 cases of OPSCC collected between January 2008 and December 2021 in the immune- histo-cytology department of the Salah Azaiez Institute. The criterion of judgement of p16 positivity in the immunohistochemi- cal study was a moderate to intense nuclear and cytoplasmic stain- ing of at least 70% of the tumour cells according to the international recommendations. Results: We included 43 cases. The median age of the patients was 63 years with a sex ratio of 2.9. Alcohol and tobacco intoxication was noticed in 44% of cases (n=19). Tumour size ranged from 7 to 80 mm with a mean size of 37 mm. Palpable cervical adenopathy was noticed in 54% of cases.