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Histopathology. 2020 Sep 17;:
Authors: Taverna C, Pollastri F, Pecci R, Giannoni B, Fattorini C, Santucci M, Mueller SK, Stoehr R, Franchi A, Agaimy A
Abstract
AIMS: Papillary neoplasms of the middle and inner ear are rare and poorly characterized. The current WHO classification lumped them into two major subtypes: aggressive papillary tumors (APTs) and endolymphatic sac tumors (ELSTs). We present two papillary neoplasms of the middle ear not fitting either classical APT or ELST, and compare them with 3 ELSTs.
METHODS AND RESULTS: Patients were a 48-year-old female and a 59-year-old male without a history of other neoplasms. Histology showed papillary-cystic growth of predominantly oncocytic (Case 1) or mucinous (Case 2) cells surrounded by p63-positive basal layer. The overall histology was reminiscent of oncocytic sinonasal papilloma (Case 1) and pancreatobiliary or salivary intraductal papillary mucinous neoplasms (Case 2). Ovarian-type stroma, invasion and malignant features were absent. Immunohistochemistry revealed expression of CK7, but not CAIX and PAX8 (except very focal PAX8 in Case 1). The TST15 gene panel (Illumina) and HRAS sequencing revealed no pathogenic mutations in BRAF, KRAS, EGFR, AKT1 or HRAS. The TruSight RNA fusion panel (Illumina) revealed a MKRN1-BRAF fusion in Case 1. No fusion was detected in Case 2. The three ELSTs showed classical features of the entity, expressed CK7, EMA, PAX8 and CAIX, and lacked a basal cell layer.
CONCLUSION: These novel cases suggest that papillary tumors of the ear represent a heterogeneous spectrum of distinct neoplasms unified by prominent papillary-cystic pattern rather than a single entity. Future studies should clarify if the MKRN1-BRAF fusion is a defining recurrent driver event, especially in those cases reported as sinonasal-type middle ear papillomas.
PMID: 32940914 [PubMed - as supplied by publisher]
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