ECP 2023 Abstracts

S296 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 teratoma shows immature tissues mixed with ectodermal and endo- dermal tissues of varying maturation. Head and neck localization is uncommon for teratomas. The majority of newborns with cervical or oral-pharyngeal teratomas have an apparent mass and an airway obstruction. Treatment requires chemotherapy and has to be further investigated for the effects on relapses. E-PS-12-056 Myoepithelial carcinoma: a case report and short review of the literature E. Souka*, G. Galanopoulos, G.M. Stanc, P. Bafaloukos, G. Sgouros, O. Tzaida *Pathology Department Metaxa Cancer Hospital, Greece Background & objectives: Myoepithelial carcinoma (MC) is a rare myoepithelial cell tumour usually of the parotid, but also submandibu- lar and minor salivary glands. It accounts for < 1% of all salivary gland malignancies, arising de novo or ex-pleomorphic adenoma (MC ex-PA). Methods: A 67-year-old male presented to the dermatology clinic with an aggravated tumour of the submandibular area. He underwent radical excision. On gross sectioning the tumour was protruding, multinodular, whitish, with focally microcystic configuration measuring 6.5cm. Results: Microscopically, the tumour was multinodular extending to the subcutis with pushing borders. The neoplasm was epithelioid, with areas of distinct clear cell morphology, indicative of myoepithe- lial differentiation. The tumour cells were arranged in solid, trabecu- lar, and cord-like pattern with myxoid, myxochondroid and focally osseous metaplastic stroma. There was a mild mitotic activity. There was no apparent necrosis, nor remnants of salivary gland or elements of pleomorphic adenoma. The neoplastic cells had a CKAE1/AE3+, CK903+, p63+, SOX10+, GFAP+, S100+ focally, SMA+ focally, CK7-, CK5/6-, HMB45- immunophenotype. Ki67 (MIB-1) was up to 3%. The tumour was signed out as myoepithelial carcinoma. Conclusion: Because of the rarity of MC there is no standard treatment guideline. Surgical resection is the main approach. In recent literature local recurrence rates 23–50 % have been reported with 25 % chance of distant metastasis. Currently, there is not a widely accepted grading system with a reproducible correlation to the prognosis. Even so pres- ence of tumour necrosis is considered by some as a high-grade feature. Patients with high-grade histopathologic markers could be good can- didates for adjuvant radiotherapy. E-PS-12-057 BRAF p.V600E-mutated papillary-cystic neoplasm of the middle ear: Expanding the spectrum of the sialadenoma papilliferum fam- ily tumours O. Stanowska*, C. Götting, M. Caversaccio, A. Agaimy, S. Weder *Institute for Tissue Medicine and Pathology, University of Bern, Switzerland Background & objectives: Papillary-cystic neoplasms of the head and neck are a heterogenous group of rare and poorly classifiable epithelial tumours. Recently, many of them were redefined as homologous neo- plasms of exocrine glands. We present a case of BRAF p.V600E-mutated middle-ear papillary- cystic lesion. Methods: 41-year-old, previously healthy female presented with left- sided otalgia, continuous hearing loss, otorrhea and tinnitus for over a year. MRI revealed tumour of the middle ear with extension to auditory tube and external auditory meatus. The patient underwent microscopic endoscopic radical tumour excision. FFPE tissue was used for H&E and immunostaining as well as for targeted Next Generation Sequencing. Results: Histology demonstrated a surface squamous inverted pap- illoma-like component with a deeper bilayered glandular component showing papillary growth of cytologically bland monomorphic colum- nar cells with eosinophilic/oncocytoid cytoplasm and apical snouts. Microabscess-like microcystic formations with epithelial and neutrophil aggregates were present in the epithelium. Immunostains showed delim- iting p63 positive basal layer around the CK7 positive glandular ele- ments. S100 was positive in the spindle cell stromal component, PAX8 faint diffuse positive in the epithelium. SOX10, TTF1, CA-9, Chro- mogranin, Synaptophysin were negative. The case demonstrated BRAF p.V600E mutation and was classified as a benign papillary neoplasm - middle ear analog to the sialadenoma papilliferum family tumours. Follow up of 11 months revealed no recurrence. Conclusion: Papillary tumours of the middle ear represent a hetero- geneous group of distinct neoplasms characterized by a prominent papillary-cystic pattern. The appropriate interpretation of histological findings and genetic alterations are necessary for their diagnosis. Exo- phytic squamous, combined with papillary-cystic ductal proliferation, evidence of the dual population of the papillae (CK7 in the ductal, p63 in the basal component), as well as presence of BRAFV600E mutation, allowed to classify the tumour as a middle ear analog to the sialad- enoma papilliferum family tumours. E-PS-12-058 Ectopic olfactory neuroblastoma (ONB) of the sellar region: report of a rare case and review of the literature M. Testa*, S. Uccella, R. D’amato Pascarella, S. La Rosa *Università degli Studi dell’Insubri, Italy Background & objectives: ONB is a non-epithelial neoplasm of the upper nasal cavities showing neuroendocrine differentiation. Anecdotic ectopic cases have been reported. We present a case of ONB of the sella, initially misdiagnosed as PitNET. The diagnostic importance of transcription factors (TFs) expression is highlighted. Methods: A 46-year-old man presented with progressively worsening visual symptoms for 7 years, with bitemporal inferior quadrantopia and scotomas. Magnetic Resonance Imaging (MRI) revealed a 41x24x37 mm sellar mass, incorporating the right carotid syphon. The patient underwent endoscopic endonasal trans-sphenoid surgery and the removed mass was sent to our Pathology Department. The specimen was entirely sampled, formalin fixed and paraffin embedded. Results: Microscopically, nests and rosettes of monotonous cells with round nuclei and scant cytoplasm were observed, showing immu- noreactivity for Chromogranin A and Synaptophysin, and question- able reactivity for ACTH (absent at a later review). Immunostains for αHCG, PRL, GH, FSH, LH were negative. The Ki67 prolifera- tion index was 5%. The original diagnosis formulated in 2016 was pituitary adenoma with ACTH immunoreactivity. Seven years later we reviewed the case and performed additional immunohistochemical studies. Tumour cells were negative for pituitary TFs (Pit1, TPIT, SF1 and GATA3) and CK8/18, but positive for SSTR2A (3+), SATB2 and OLIG2; S100 and GFAP highlighted positive sustentacular cells. A final diagnosis of ectopic ONB was rendered. Conclusion: ONB is a rare neoplasm. Ectopic cases have been reported in maxillary sinus, ethmoidal bulla and sinus, lacrimal sac, nasopharynx, pterygopalatine fossa. Only 7 cases of sellar ectopic ONBs have been reported in literature so far. In our case, tTFs proved to be reliable tools for the differential diagnosis. TFs must be included in the immunohistochemi- cal panel for the diagnostic management of all sellar region lesions as they are essential for PitNETs classification and to rule out potential mimickers. E-PS-12-059 Agnostic and potential agnostic biomarkers and their relationship with prognosis in squamous cell carcinomas of the larynx: in silico evaluation M.H. Toper*, A. Tan, S. Sarioglu *Dokuz Eylul University, Turkey