n, pl  -to*mas  or  -to*ma*ta   1  :  an epidermoid cyst usu. in the brain arising from aberrant embryonic rests and appearing as a compact shiny flaky mass - called also pearly tumor   2  :  a tumor usu. growing in a confined space (as the middle ear or mastoid) and frequently constituting a sequel to chronic otitis media cho*les*te*a*to*ma*tous adj 
 
    
 
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