An extraosseous aneurysmal cyst in the pelvic cavity: report of a case.

A 51-year-old Japanese female was referred to us with a left lower quadrant pain and palpable mass. The CT and MRI study showed a 10x8x8 cm of well-circumscribed, multicystic mass adjacent to the left iliac bone. The mass was excised and consisted of multiple cysts containing bloody viscous material surrounded by thin-ring of eggshell-like tissue. The histological findings correlated with those of an aneurysmal bone cyst. This extraosseous case might be the first reported case observed in the pelvic cavity.