Femoral Neck-Aneurysmal Bone Cyst

Source:  Femoral Neck-Aneurysmal Bone Cyst    Tag:  fibrous dysplasia pictures

22 year old male with history of fall and pain right hip. X-ray shows expansile lucent predominantly intramedullary, femoral neck lesion with normal hip joint. MR shows grossly expansile septated, predominantly fluid signal intensity space occupying lesion with cortical breaches, bleed, soft tissue edema in the vicinity – Features are suggestive of aneurysmal bone cyst.

Teaching Points by Dr MGK Murthy, contributors-Mr Hariom Sharma

ABC is non-neoplastic expansile lesion consisting of blood filled spaces separated by connective tissue septa containing bone or osteoid and osteoclast giant cells 

Etiology unknown 

May be primary or secondary ( in about 30 % of associated bone tumors).

CT suggests 20 HU as approximate density with presence of blood and fluid levels.

Double density fluid levels on MR are suggested as quite specific to ABC.

Differential diagnosis includes Simple Bone cyst (Centrally located with no expansion / cortical breach), GCT (more than 20 years of age, no significant expansion and predominantly epiphyseal lesion),  Osteoblastoma (usually diaphyseal, no fluid / fluid levels or cortical breach), Telengiectatic osteosarcoma / Angiosarcoma (difficult to differentiate from agressive ABC).