ECP 2023 Abstracts

S292 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 media. An exploratory tympanotomy was planned and revealed a tumoral lesion adhered to hypotympanum, ossicular chain and incu- dostapedial joint with free clear serous liquid in cavity, highly suspi- cious of glomus tumour. Lesion was partially excised and morphologic description was performed. Results: Gross examination revealed multiple red-whitish tissue frag- ments with moderate consistency. Microscopically, it was formed by nervous tissue without significant morphological alterations with some associated singled-lined glandular structures without atypia and sur- rounded by loose stroma with mild chronic inflammatory cell infiltrate. Immunohistochemistry revealed strong positivity to GFAP. Findings propose differential diagnosis between acquired encephalocele and middle ear neuroglial heterotopia, which are differentiated by connec- tion or not with the brain. However, presence of glandular structures suggests the former because it is considered a metaplastic change, but radiological is still needed. A later CT revealed a 6 mm solution of continuity in the posterior region of tegmen tympani, therefore surgical reparation was planned. Conclusion: Given the rarity of acquired encephalocele, few large series exist in the literature, and optimal surgical management remains controversial, but it is recommended to decrease the incidence of men- ingitis. Pathological examination of specimens is still important and impacts directly in patient care. E-PS-12-041 Extramedullary plasmacytoma in nasopharynx. Case report and literature review J.S. Marrero Afonso*, S. Carrión Marrero, K.M. Gallardo Rodríguez, C. Febles Pérez *Spain Background & objectives: Extramedullary plasmacytoma represents a rare entity among the plasma cell neoplasms which are treated with radiation alone. Because of nonspecific radiological findings, its wide differential diagnosis in head and neck area, rarity and clinicopatho- logical characteristics could justify its presentation. Methods: We report a 52 years-old male non-smoker patient who pre- sented a 2 years history of intermittent epistaxis in left nasal fossa. A CT showed mucosal enhancement in nasopharynx and nasal fibros- copy revealed hematic material rests which were adhered to middle turbinate, highly suspicious of haemangioma. Therefore, an incisional biopsy was planned, and morphologic description was performed. Results: Gross examination revealed multiple reddish tissue fragments with moderate consistency. Microscopically, there was haemorrhagic material and a proliferation of plasmacytoid cells with homogenous eosinophilic cytoplasm, peripherally placed hyperchromatic nuclei, sometimes with conspicuous nucleoli and irregular contour. Immuno- histochemistry revealed positivity to CD138, CD20, EMA and cyclin D1 with negativity to vascular markers, CK AE1/AE3, S100, CD45, CD3, CD5, CD79a, CD56, MUM1, BCL2, EBV, HHV8 without mono- typic expression of light chains. A provisional diagnosis of plasma cell neoplasm was made. Patient had no clinical suggestive of multiple myeloma or bone marrow infiltration. Therefore, a final diagnosis of extramedullary plasmacytoma was made and the patient underwent radiotherapy (40Gy) with complete response to treatment. Conclusion: Extramedullary plasmacytoma is an infrequent entity that should be taken into account in differential diagnosis of head and neck region that includes carcinoma, melanoma and other lymphomas. Pathological examination of specimens is still important and impacts directly in patient care. E-PS-12-042 Nasopharyngeal hairy polyp in a male adult: a case report N. Menezes*, A. Lança Neto, M. Mendes Las Casas Moreira, F. Fernandes Guimarães, C. Issa De Azevedo *Laboratório Dairton Miranda, Faculdade de Ciências Médicas de Minas Gerais, Brazil Background & objectives: Hairy polyp is a benign polypoid lesion usually located in the nasopharynx. This report intends to describe a rare lesion that might be unknown to surgical pathologists in general and highlight the possibility of management issues by the pathologists. Methods: We describe a case of a 58-year-old male who has pre- sented intermittent and purulent otorrhea since infancy. The patient was referred to an otorhinolaryngologist to investigate the cause of these symptoms. A sinonasal videoendoscopy and a videolaryngos- copy incidentally identified a polypoid mass in the left region of his nasopharynx compatible with squamous cell papilloma or carcinoma which was biopsied later. Results: The gross analysis of the specimen demonstrated a polypoid whitish tissue fragment measuring 0,6x0,4x0,3cm with an irregular surface. Microscopically it showed a polyp covered by an ectodermal layer characterized by keratinizing squamous epithelium with underly- ing associated adnexal structures, including hair follicles and sebaceous units. There was also a combination of mesodermal tissue including adipose tissue and skeletal muscle. The primary histological analysis initially raised the possibility of any error during the analytical phase (identification of the block, embedding, cutting, identification of the slide). A detailed check excluded an error and then the diagnosis of hairy polyp was rendered after a search in Head and Neck WHO Blue Book. Conclusion: Surgical excision is the best therapeutic procedure and is curative in the majority of cases. Hairy polyps are important differential diagnosis in neonate patients presenting with upper airway obstruction, but they can also be rarely found in adults. In these cases, appropriate knowledge about these malformations guides the management. The histological findings of mature and typical mesodermal and ectodermal tissues forming a polypoid lesion in the nasopharynx defines the diag- nosis of hairy polyps and guides the patient’s prognosis and follow-up. E-PS-12-043 Sclerosing odontogenic carcinoma - a case report of a rare lesion K. Moutasim*, R. Webb *University Hospital Southampton, United Kingdom Background & objectives: A 34 year old man was referred by his doctor to the oral and maxillofacial surgery department complaining of discomfort over 3/52 in the upper right quadrant. A radiolucent lesion was noted in association with the UR4 tooth. Methods: OPG imaging showed a well-defined cystic lesion that had caused resorption of the upper right 4 tooth roots. A CT scan showed a radiolucent 2.5cm lesion in the right maxilla, which had displaced the alveolus in the premolar region. Excision biopsy was performed. Results: Histological feature showed an epithelial tumour composed of bland strands and cords of epithelial cells within a densely slcerotic stroma. There were foci of perineural invasion. The differential diagnosis included sclerosing odontogenic carcinoma, as well as muco-epidermoid carcinoma, odontogenic fibroma, hyalinis- ing clear cell carcinoma or squamous odotongenic tumour. There was no evidence of keratinisation and no intracytoplasmic mucin was seen on PAS staining. There was no EWSR1 gene rearrangement on genomic studies. There was no amyloid on Congo Red staining. The epithelial cells were positive with CK19 immunohistochemistry. Taken together, the features were interpreted as those of a sclerosing odontogenic carcinoma (SOC). Conclusion: SOC is a rare odontogenic carcinoma, comprising thin cords of epithelial cells in a slcerotic stroma with often striking peri- neural invasion. The patient is under follow-up and two years later, remains well with no evidence of recurrent or metastatic disease on imaging.