= CODMAN TUMOR = BENIGN CHONDROBLASTOMA = CARTILAGE-CONTAINING GIANT CELL TUMOR

= benign cartilaginous tumor with predilection for growing skeleton

Frequency: 1% of primary bone neoplasms (700 cases in world literature)

Age: peak in 2^nd decade (range, 8–59 years); 10–26 years (90%); M÷F = 2÷1; occurs before cessation of enchondral bone growth

Path: derived from primitive cartilage cells

Histo: polyhedral chondroblasts + reactive multinucleated giant cells + nodules of pink amorphous material (= chondroid) = epiphyseal chondromatous giant cell tumor (resembles chondromyxoid fibroma); “chicken wire” calcification of matrix = pericellular deposition of calcification is virtually PATHOGNOMONIC

• symptomatic for months to years prior to treatment
• mild joint pain, tenderness, swelling (joint effusion)
• limitation of motion

Location:

1. long bones (80%): proximal femur + greater trochanter (23%), distal femur (20%), proximal tibia (17%), proximal humerus (17%)
   • ⅔in lower extremity, 50% about knee
   • may occur in apophyses (minor + greater trochanter, patella, greater tuberosity of humerus)
2. flat bones: near triradiate cartilage of innominate bone, rib (3%), vertebral body & posterior elements (1.4%)
3. short tubular bones of hand + feet

Site: eccentric medullary, subarticular location with open growth plate (98% begin within epiphysis); tumor growth may continue to involve metaphysis (50%) + rarely diaphysis

• oval / round eccentrically placed lytic lesion of epiphysis
• 1–4 cm in diameter occupying <½ of epiphysis
• well-defined sclerotic margin, lobulated in 50%
• stippled / irregular calcifications in 25–30–50% (cartilaginous clumps better visualized by CT)
• intact scalloped cortical border
• thick periosteal reaction in metaphysis (50%) / joint involvement
• periostitis of adjacent metaphysis / diaphysis (30–50%)
• growth plate open in majority of patients

MR:

• MR tends to overestimate extent + aggressiveness ← large area of reactive edema!
• intermediate to low SI on T2WI relative to fat ← immature chondroid matrix, hypercellularity, calcifications, hemosiderin
• extensive intramedullary signal abnormalities ← bone marrow edema
• peripheral rim of very low signal intensity
• hypointense changes on T1WI + hyperintense on T2WI in adjacent soft tissues (← muscle edema in 50%)
• ± joint effusion

Prognosis: almost always benign; may become locally aggressive; rarely metastasizes

Dx: surgical biopsy

Rx: curettage + bone chip grafting (recurrence in 25%)

DDx:

1. Ischemic necrosis of femoral head (may be indistinguishable, more irregular configuration)
2. Giant cell tumor (usually larger + less well demarcated, not calcified, older age group with closed growth plate)
3. Chondromyxoid fibroma
4. Enchondroma
5. Osteomyelitis (less well-defined, variable margins)
6. Aneurysmal bone cyst
7. Intraosseous ganglion
8. Langerhans cell histiocytosis (less well-defined, variable margins)
9. Primary bone sarcoma