Intra-osseous ganglion of the proximal humerus: a case report.

We report a 72-year-old woman with a type-1 intra-osseous ganglion in the proximal humerus, extending to the bone surface. We conducted a systemic review of intra-osseous ganglion cases in Japan to identify clinical features and pathogenesis of this condition. The anatomical distribution between intra-osseous ganglia without a communicating soft tissue ganglion (type 1) and those with (type 2) is different. The origins of intra-osseous ganglia vary and depend on their anatomical location. They can arise from within the bone or in the adjacent soft tissue, and can progress to a type-2 lesion in either an outside-in or inside-out fashion.