The phospholipid content, one product of the keratinization process, of the transitional zone and keratin layer was studied in 60 middle ear specimens with clinical cholesteatoma and 16 specimens without cholesteatoma, using mainly Mallory's and Baker's staining methods. The Mallory staining pattern was distorted by fixation in formalin, and to a lesser degree in alcohol, and only in fresh cryostat sections without fixation was the phospholipid removable by lipase. The cryostat sections gave identical results with both staining methods, the granules showing strong staining while keratin staining was variable. In noncholesteatomatous squamous epithelium the keratin layer was very thin or absent but the granular cell layer showed distinct phospholipid staining, comparable to the one seen in cholesteatoma epithelium.
Palva T, Palva A, Dammert K. Keratin in Middle Ear Squamous Epithelium. Arch Otolaryngol. 1972;95(3):214–220. doi:10.1001/archotol.1972.00770080356006
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