Most accepted theory for the formation of secondary cholesteatoma:
According to this theory, chronic negative middle ear pressure (which occurs due to poor Eustachian tube function and chronic inflammation of the middle ear) leads to retractions of the structurally weakest area of the tympanic membrane, the pars flaccida. Once the retractions form, the normal migratory pattern of the squamous epithelium is disrupted, resulting in the accumulation of keratin debris in the cholesteatoma sac..
Congenital
Squamous metaplasia
Ingrowth of squamous epithelium
Retraction pocket