Why does middle ear cholesteatoma recur?

Mucosal biopsy specimens were taken from 75 ears undergoing surgery for chronic ear disease. The specimens were studied for squamous epithelium under the operation microscope, and findings during surgery were recorded for comparison with the results of the histologic examination. In 13 ears (17.3%) the histologic study disclosed squamous epithelium in the biopsy specimens that had been clinically judged to be free of such epithelium. Most specimens contained full-thickness squamous epithelium with some surface keratin. In some specimens up to 3 mm long strips of squamous epithelium without granular cell layer were observed. These areas represented the advancing front of squamous epithelium capable of producing mature squamous epithelium. The positive specimens were all well separated from the clinical cholesteatoma and were either extensions over the perforation edges or from the cholesteatoma epithelium in the middle ear or mastoid. Apparently, this unrecognized and nonremoved squamous epithelium is the main reason for the high incidence of cholesteatoma recurrence reported by some surgeons.