J Int Adv Otol 2017 • DOI: 10.5152/iao.2017.4049 Letter to Editor Dear Editor, Recently, EAONO/JOS’s joint consensus paper on defnitions, classifcation, and staging of middle ear cholesteatoma was published 1 . As it is the era of collection of and report on uniform and comparable data, this is a welcome consensus statement. Currently, we are setting up a new nationwide multicenter study in the Netherlands, entitled Dutch Cholesteatoma Data, in which we would like to implement this guideline. To inform colleagues about our local experiences and choices so far, we are writing this letter. Although the EAONO/JOS consensus statements are clearly presented, we encountered some difculties with the classifcation. First, we believe that the divisions of the middle ear space need further specifcations. The anatomical sites as presented in the fg- ure and the text of the consensus statements 1 can be variously interpreted and show some “blank spots.” For instance, the borders used for the anterior epitympanic space are unclear, which, in addition to the variation in anatomy and exposition in this area (canal wall up, canal wall down, microscopic, and endoscopic), will most likely result in a non-uniform registration. Second, we strongly believe that there is a primary need to elaborate on the classifcation rather than simplify it with a staging system. Gathering classi- fcation data on extent, complication, and ossicular state, using an easy format will make it possible to monitor surgical outcomes. This will allow comparisons of data among diferent hospitals, publications, and classifcations. When large numbers of data on outcomes in relation to classifcation become available, results can be used to propose diferent stages. To improve the practical applicability of the EAONO/JOS joint statement in our national study, we have proposed to our participating ENT surgeons the following modifcations: 1. The borders of divisions of the middle ear and mastoid are further defned, and consequently, the fgure of the consensus paper is refned [1] . In the EAONO/JOS consensus statement, the middle ear and mastoid spaces are divided into four sites to classify the extent of the cholesteatoma: difcult access sites (S), tympanic cavity (T), attic (A), and mastoid and antrum (M). The difcult access sites (S) fur- ther include S1 (the supratubal recess) and S2 (the sinus tympani). We propose to defne the anatomical divisions of the middle ear and mastoid in more detail using surgical and anatomical landmarks. These landmarks based on a selection of published papers on this topic are highly likely to be identifed both on CT scans and during all types of surgical approaches and are thus less prone to various interpretations [2-4] . Table 1 summarizes our suggestions for further specifcation of borders between the diferent sites of the middle ear and mastoid. In addition, Figure 1 shows the updated illustration based on those refned borders. An advantage of a more detailed description of these borders can be illustrated by the following examples that describe the dif- ference between A and S1 anterior. In case a cholesteatoma extends to the head level of the malleus, but not further anteriorly, Implementation of the “EAONO/JOS Defnitions and Classifcation of Middle Ear Cholesteatoma” - from STAM to STAMCO Paul Merkus, Fleur A. ten Tije, Mariska Stam, Frederique M.L. Tan, Robert Jan Pauw Department of Otolaryngology-Head and Neck Surgery, section Ear & Hearing, VUmc Amsterdam Public Health Research Institute, Amsterdam, Netherlands (PM, FT, MS) Department of Otolaryngology-Head and Neck Surgery, Erasmus MC Rotterdam, Rotterdam, Netherlands (FT, RJP) Corresponding Address: Fleur A. ten Tije E-mail: dcd@vumc.nl Submitted: 20.05.2017 • Accepted: 09.06.2017 • Available Online Date: 17.07.2017 ©Copyright 2017 by The European Academy of Otology and Neurotology and The Politzer Society - Available online at www.advancedotology.org Cite this article as: Merkus P, Tije FA, Stam M, Tan FML, Pauw RJ. Implementation of the “EAONO/JOS Defnitions and Classifcation of Middle Ear Cholesteatoma” from STAM to STAMCO. J Int Adv Otol 2017; DOI: 10.5152/iao.2017.4049.