| Histopathologically, serous otitis media is
characterized by the presence of a thin effusion with no or few
inflammatory cells. The effusion is considered to be the product of a vascular
transudate and can be accompanied by edema of the subepithelial layer.
Epithelial changes at this stage are minimal.
The etiology of this type of effusion is commonly Eustachian tube
dysfunction, but it may also be seen in cases of primary or metastatic
cancer of the tympanic cavity, or after a prolonged period on a
respirator. The following
is an example of serous otitis media.