Solitary unicameral bone cyst is properly to be regarded as an independent and distinctive lesion and ought not to be included, as it still rather often is, within the omnibus and unjustifiable category of localized fibrocystic disease of bone. It is a relatively uncommon lesion and manifests itself mainly in childhood and adolescence. Nearly always it develops in the shaft of some one of a few predilected long tubular bones, and, in particular, the upper portion of the humeral shaft accounts for about one half of the localizations. Indeed, throughout this discussion, except when we are referring specifically to other localizations, we will have in mind the cyst as it appears in long bones. Briefly and generally, the lesion can be described as a fairly large fluid-filled unicameral cavity, located in the interior of the affected bone shaft and delimited by a more or less thinned and expanded shaft cortex