Schematic illustration of the expansion stage written by Sudhoff and Tos [24]. (a) Expansion of sinus cholesteatoma, and the lakes of keratin are opened to the surface of the retraction wall in the depth the cones are proliferating and growing. Lateral migration and cell cleaning is superficially still possible (arrow) (reproduced with modification with permission from [24]). (b) The cholesteatoma has expanded by the length of the cone. In the depth, new microcholesteatoma are formed within the new cones (reproduced with modification with permission from [24]). (c) The keratin lakes are fused, moving the border of the matrix further towards the attic (reproduced with modification with permission from [24]). (d) Further expansion of attic cholesteatoma. Establishment of a vicious circle in the following ways: proliferation at the bottom of the cone, keratin formation within the cones, fusions of microcholesteatomas, and further accumulation of keratin leading to further deterioration of cell cleaning (reproduced with modification with permission from [24]).
