(A830) Histologic Correlates of European Academy of Otology-Neurotology/Japan Otologic Society (EAONO/JOS) Cholesteatoma Classification

Introduction: Current classification of acquired middle ear cholesteatoma (MEC), devised by
EAONO/JOS (2017) divides it into 7 groups: the ones originated from retraction
pockets in pars tensa (PTRP), in pars flaccida (PFRP), involving both pars tensa and
flaccida (PTPFRP); tympanic membrane (TM) perforation originated (TMP);
traumatic/iatrogenic (TI); residual (Res) and recurring (Rec) MECs. Cholesteatoma is
a clinical diagnosis; therefore, histopathologic confirmation is rarely indicated. We,
however, routinely examine surgical samples to rule out pathologies that superposed
or mixed with MEC. The aim of this study is to test the histologic relevance of the
clinical MEC classification of EAONO/JOS.

Methods: The study was conducted on the pathologic archive specimens from consecutive
patients allocated to the above groups (excluding TI) retrospectively. Additionally,
PTRP cholesteatomas were split into two groups: sinus tympani (ST) and adhesion-
originated (Adh) ones. Following parameters were looked for in the
Hematoxylene&Eosine stained slides in both matrix and perimatrix and graded 0-3
according to the number or size: neutrophil, plasma cell, lymphocyte, fibroblast,
keratinocyte counts; neovascularization and epithelium thickness. Presence of
Langhans giant cells, tympanosclerotic plaques, cholesterin clefts, basal membrane
defects were taken as binary variables.

Results: Inflammatory cells were most numerous in PFRP matrix and perimatrix, least
numerous in ST matrix. In perimatrix no significant difference was found in any
parameter between the groups except residues, Acanthosis and keratinocyte
hyperplasia was present in all, yet, more intensely in pars flaccida involving groups.
Basal membrane gaps appeared only in two of the specimens.

Conclusions: These findings indicated predominance of inflammatory cells and metaplastic
changes across the groups. Basal membrane defects do not seem to play a major
role in MEC pathogenesis. Histologic differences among the groups correspond with
clinical categories. However, pars tensa retraction origin ST and Adh groups
somewhat differ histologically.