Aneurysmal Bone Cyst (ABC)

 

Epidemiology:

    • 1st two decades

 

Common sites:

    • metaphysis of long bones (most)

 

Gross features:

    •  

 

Histologic features:

    • spaces separated by septa
      • spaces containing serum or blood
      • septa composed of loose arrangement of spindle cells interposed with giant cells
        • fine line of osteoid (fiber-osteoid) just beneath lining of septum
    • solid areas:
      • loose arrangement of spindle cells
      • brisk mitotic activity
      • no atypia
      • fine lace-like / trabecular osteoid
      • characteristic calcified matrix
    • solid aneurysmal bone cyst:
      • only solid areas

 

Immunophenotype:

Marker:

Sensitivity:

Specificity:

 

 

 

 

Molecular features:

    • t(16;17)(q22;p13)
      • CDH11-USP6 fusion

 

Other features:

    • not a true neoplasm
    • recur in 20% after curettage
    • may be “secondary” to other conditions (giant cell tumour, chondroblastoma, fibrous dysplasia)
    • radiology:
      • lytic destructive lesion
      • metaphysis of long bones
      • eccentric
      • “blowout” appearance
      • eggshell appearance
      • fluid levels on CT
      • honeycomb appearance with fluid levels on MRI
      • margins may be indistinct
      • may mimic malignant tumour

 

References:

    • Sternberg 1998