Other tumors of bone
Aneurysmal bone cyst (ABC)

Author: Nat Pernick, M.D. (see Authors page)

Revised: 16 August 2018, last major update June 2005

Copyright: (c) 2003-2018,, Inc.

PubMed search: aneurysmal bone cyst (ABC)

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Cite this page: Pernick, N. Aneurysmal bone cyst (ABC). website. Accessed December 18th, 2018.
Definition / general
  • Uncommon; expanding osteolytic lesion of blood filled spaces of variable size separated by connective tissue septa with osteoclast giant cells and variable reactive bone
  • Usually ages 1 - 20 years, no gender preference
  • Benign but grows rapidly; simple curettage is followed by recurrence in 20%; rarely transforms to osteosarcoma
  • Sites: metaphysis of posterior vertebrae (often multiple), flat bones, shaft of long bones; rarely within wall of major artery or in soft tissue (Am J Surg Pathol 2002;26:64, Am J Surg Pathol 1994;18:632, Am J Surg Pathol 1993;17:1062)
  • May also be secondary to trauma or arise in preexisting bone lesion (giant cell tumor, chondroblastoma, fibrous dysplasia)
Radiology description
  • Eccentric expansion of bone, cortical erosion and destruction, small peripheral area of periosteal bone formation
  • Fluid levels detectable by CT
  • MRI shows honeycomb appearance with fluid levels
  • 25% recur after curettage so aggressive curettage with bone grafting or en bloc resection recommended
Gross description
  • Spongy, hemorrhagic mass covered by thin shell of reactive bone
  • Small amount of tissue compared to large size of lesion on Xray
Microscopic (histologic) description
  • Large cystic spaces filled with blood and separated by fibrous septa, alternating with solid areas
  • Cysts and septa lined by fibroblasts, myofibroblasts and histiocytes but not endothelium
  • Clusters of osteoclast-like multinucleated giant cells with loose spindly stroma to cellular stroma, reactive woven bone, degenerated calcifying fibromyxoid tissue
  • Variable mitotic figures and hemosiderin
  • No malignant osteoid, no atypia
Microscopic (histologic) images

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Quiz case

Molecular / cytogenetics description
Differential diagnosis
Additional references