Osteoma of the mastoid is so rare that only recently has this subject been given some clarification. Proof of its rarity is the fact that only 28 cases have been reported in all medical literature.
Osteoma of the mastoid should not be confused, as is often done, with exostosis of the external auditory canal. The latter condition invariably arises from the tympanic portion of the temporal bone, and this anatomic situation alone distinguishes it from osteoma of the mastoid process.1
The otolaryngologist usually sees osteoma in the lumen of the frontal sinus or in the ethmoid capsule, but rarely in the mastoid region. When the growth is found in the mastoid region it can be classified as a true osteoma rather than as an exostosis or a hyperostosis.2
Histologically there are three types of osteoma of the mastoid:
Osteoma compactum, or osteoma eburneum, occurs more frequently than the other
CINELLI AA. OSTEOMA EBURNEUM OF THE MASTOID. Arch Otolaryngol. 1941;33(3):421–424. doi:10.1001/archotol.1941.00660030425008
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