= expansile pathologically benign lytic lesion of bone containing thin-walled cystic cavities filled with chronic blood products; name derived from roentgen appearance

Incidence: 1.4–2.3% of primary bone tumors

Etiology:

1. primary ABC (65–99%):
   • local circulatory disturbance ← trauma
   • improper repair of traumatic subperiosteal hemorrhage
2. secondary ABC (29–35%) hemorrhage into a preexisting bone lesion → venous obstruction / arteriovenous fistula:
   • common: giant cell tumor (19–39%), osteoblastoma, angioma, chondroblastoma
   • uncommon: fibrous dysplasia, fibrous histiocytoma, chondromyxoid fibroma, xanthoma (= nonossifying fibroma), eosinophilic granuloma, telangiectatic osteosarcoma, metastatic carcinoma, solitary bone cyst

Histo: lack of anaplasia

1. “intraosseous arteriovenous malformation” with cystic honeycombed spaces filled with blood separated by spindle cell stroma + osteoclast-like giant cells and osteoid / bone production; mineralized chondroidlike material in ⅓; areas of free hemorrhage
2. solid variant of ABC in 5–7%: proliferation of spindle cells

Types:

1. INTRAOSSEOUS ABC
   = primary cystic / telangiectatic tumor of giant cell family, originating in bone marrow cavity, slow expansion of cortex; rarely related to history of trauma
2. EXTRAOSSEOUS ABC
   = posttraumatic hemorrhagic cyst; originating on surface of bones, erosion through cortex into marrow

Peak age: peak age 16 (range, 10–30) years; in 75% <20 years; F >M

• pain of relatively acute onset with rapid increase of severity over 6–12 weeks; ± history of trauma
• neurologic signs (radiculopathy to quadriplegia) if in spine

Location:

• spine (3–20%): thoracic (34%), lumbar (31%), cervical spine (22%), sacrum (13%); involvement of posterior elements with extension into vertebral body (75%); may involve two contiguous vertebrae (25%) / intervertebral disk / ribs / paravertebral soft tissues
• long bones: eccentric in metaphysis of femur, tibia, humerus, fibula
• pelvis

• purely lytic eccentric radiolucency
• aggressive expansile ballooning lesion of “soap-bubble” pattern + thin internal septations + trabeculations
• rapid progression within 6 weeks to 3 months
• sclerotic inner portion
• almost invisible thin cortex (CT shows integrity)
• tumor respects epiphyseal plate
• no periosteal reaction (except when fractured)

CT:

• “blood-filled sponge” = fluid-fluid / hematocrit levels ← blood sedimentation (in 10–35%)
• ± mineralized chondroidlike material when abundant

MR:

• multiple cysts of different SI representing different stages of blood by-products:
  • heterogeneous fluid-fluid levels within loculations ← hemorrhage with sedimentation
  • ↑signal intensity on T1WI ← methemoglobin
• low-SI rim ← intact thickened periosteal membrane
• heterogeneous enhancement:
  • smooth enhancement of internal septa

NUC:

• “doughnut” sign = moderate to intense radiotracer accumulation at lesion periphery (64%)

Angio:

• hypervascularity in lesion periphery (in 75%)

Prognosis: 20–30% recurrence rate

Rx: preoperative embolotherapy; complete resection; radiation therapy (subsequent sarcoma possible)

Cx:

1. Pathologic fracture (frequent)
2. Extradural block with paraplegia

DDx:

1. Giant cell tumor (particularly in spine)
2. Hemorrhagic cyst (end of bone / epiphysis, not expansile)
3. Enchondroma
4. Metastasis (renal cell + thyroid carcinoma)
5. Plasmacytoma
6. Chondro- and fibrosarcoma
7. Fibrous dysplasia
8. Hemophilic pseudotumor
9. Hydatid cyst