Learning Objectives: 1. To define and classify the cholesteatomas and the spreading routes followed by the disease.; 2. to understand a novel model of pathogenesis with special emphasis on the key role of tympanic membrane retractions; 3. to employ an algorithm to aid the decision making process to maximize surgical results.

Cholesteatoma is a very intriguing condition and still poses a challenge to the otologist. Since it was first described by Duverney in 1683 it has been extensively studied but there are still many pending questions about its development, natural history and prognosis. In 2015 our group proposed a new and embracing classification system for acquired cholesteatomas based on pathogenesis. Our recent studies have shown differences in cholesteatoma growth patterns between children and adults and demonstrated the effect of the disease in the inner ear in both groups. Our contralateral ear studies have also confirmed the essential role of tympanic membrane retractions in the pathogenesis of cholesteatoma.