ECP 2023 Abstracts

S294 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 adenomas that develop malignancies. This typology could prove use- ful at the clinical level, without compromising the accuracy of the pathological diagnosis. E-PS-12-049 Chondromesenchymal hamartoma and DICER-1 mutation: a case report and literature review A. Prat*, L. López, M.C. Campos, D. Piñol, J.R. Gras, M. Casasayas, J. Szafranska *Hospital de la Santa Creu i Sant Pau, Spain Background & objectives: Nasal Chondromesenchymal Hamartoma (NCMH) is a rare benign lesion of sinusoidal tract, predominantly affecting children and young adults, associated with DICER1 muta- tion. Our aim is to describe NCHM and its association with DICER1 syndrome. Methods: We present a case of an isolated nasal mass in a 22-year-old women with anosmia and hyposmia, without relevant personal or fam- ily history. Clinical exploration revealed polypoid lesion, measuring 50x40x10mm extending from cribiform plate to nostril. The patient underwent endoscopic sinonasal resection surgery. Routine studies with H&E and immuno-stains were performed. Results: Microscopically, the case is described as a polypoid lesion containing variable-size cystic spaces filled with mucoid acellular material, lined by pseudostratified ciliated epithelium, respiratory-type. Cysts were admixed with nodules of cartilage variably in size, shape and contour with myxo-hyaline loose stroma, formed by spindle cells without atypia in a background of mixed inflammatory cells. Mor- phological characteristics confirmed NCHM and DICER1 immuno- stain turned out positive. Patient went through genetics consultation to exclude DICER1 germline mutation, which resulted negative. Conclusion: DICER1 mutation carriers have a predisposition for development of various tumours, most commonly pleuropulmonary blastoma, thyroid, kidney and ovary cancers. The presence of NCMH in young patients, which is rare tumour not included in current WHO classification, can be associated with DICER1 germline or somatic mutations, are frequently overlooked by pathologists. Hence, genetical studies should be performed in those cases to exclude it. E-PS-12-050 Case report: Epithelial-myoepithelial carcinoma in the nasal cav- ity- a diagnostic pitfall in frozen section evaluation T. Rattay*, J. Knolle, C. Taege, A. Haak, J. Lautermann *Krankenhaus Martha-Maria Halle-Dölau, Institut für Pathologie, Germany Background & objectives: Epithelial-myoepithelial carcinoma (EMC) is a rare low to intermediate grade malignant salivary gland tumour mostly occurring in the major salivary glands. A less common site of appearance are the seromucinous glands of the sinonasal tract. Methods: A 69-year-old male patient presented with progressive pressure pain on the left cheek and left eye. Endoscopic examination showed a polypoid mass in the left nasal cavity. CT and MRI further revealed an expansive mass with bone destruction of adjacent struc- tures: the medial nasal concha, the medial wall of the maxillary sinus and of the left orbita. Results: Before tumour excision a biopsy was taken. Frozen section showed an invasive papillary epithelial lesion without nuclear atypia, suspicious for inverted papilloma. On paraffin embedded tissue sec- tions this diagnosis was initially confirmed. Complete excision of the tumour was performed. Shortly afterwards the tumour recurred locally. Histology now showed an invasive biphasic tumour with tubular and cribriform growth pattern composed of luminal ductal and outer myoepithelial cells. Immunohistochemically the luminal cells were strongly positive for CK8/18 and CD117 while the myoepithelial cells stained positive for smooth muscle actin and P63. Molecular analysis was performed and revealed a loss of PTEN. A diagnostic HRAS muta- tion was not detected. Conclusion: Although the occurrence of EMC in the nasal cavity is extremely rare, pathologists must consider it. Diagnosis is based on the biphasic architecture and the immunophenotype. Especially his- tological variants can be challenging to diagnose. HRAS mutations can help to rule out EMC mimics. Sometimes only reconsidering the chosen analytical approach as much as peer review leads to the correct diagnosis. E-PS-12-051 Pharyngolaryngeal amyloidosis. Five years experience in a single institution M.G. Rodríguez Guevara*, C.J. Martinez Martinez, S. Fernández Cas- cón, J. Alzoghby-Abi-Chaker, O. García-Galvis, S. Marín-Asencio, E. Honrado-Franco, S. Sáez-Ávarez *Complejo Asistencial Universitario de León, Spain Background & objectives: Head and neck amyloidosis is rare, being the laryngeal the most common location. However, this last area repre- sents less than 1% of all benign lesions of the larynx, and it is usually manifests as a form of localized amyloidosis. Methods: Since 2018 until 2022 (included), a retrospective analysis of diagnosed cases of laryngeal amyloidosis have been performed in our centre. Based on this, a systematic search was carried out in the specialized database (PatWin), considering all diagnoses with laryn- geal amyloidosis. The clinical and morphological data were collected and analysed. Results: We have identified 2 patients with Laryngeal and 1 patient with Pharyngeal Amyloidosis, which correspond to two men and one woman between the third and fourth decade of their life. Recurrent dysphonia was a common symptom for all consulted patients after continuous vocal effort. In the first case, the cervical CT revealed a small smooth lesion in the right posterior pharyngeal wall, in the other 2 cases a thickening of the soft tissues with isolated calcifications was observed. The pathology study revealed a subepithelial deposit of acel- lular, eosinophilic, and amorphous material, which stains with Congo red and offers apple-green birefringence, as well as immunoreactivity with P amyloid. Conclusion: Laryngeal amyloidosis is a rare entity that clinically mani- fests in a very non-specific manner and can be confused with other enti- ties such as vocal cord polyps, lipoid proteinosis, among others, which are negative for Congo Red. It usually presents locally in this area, although it can occur in association with a systemic disease (multiple myeloma, neuroendocrine tumour, small cell carcinoma, etc.), or as an initial manifestation of it. For this reason, multidisciplinary manage- ment of these patients is necessary. E-PS-12-052 Pleomorphic adenoma of the parotid gland with canalicular ade- noma-like morphology: a recently recognized distinct subtype F. Rosa*, M. Rito, J.A. Ortiz-Rey, C. Martins, I. Fonseca *Instituto Português de Oncologia de Lisboa Francisco Gentil, Portugal Background & objectives: Pleomorphic Adenoma (PA) derives its name from the significant cytomorphological and architectural diver- sity it can display. Notably, a specific tumour may only have a single pattern. Most PAs harbour gene fusions involving PLAG1 (>50%) or HMGA2 (10-15%) genes. Methods: We present a case of a PA of the parotid with a prominent canalicular adenoma (CA)-like pattern, similar to the characteristic minor salivary gland CA and creating a diagnostic dilemma. The case was investigated by FISH using a break-apart probe for HMGA2 gene. Review of the literature was performed.