Bone and Soft-Tissue Disorders
- CHILDHOOD
Most common malignancy of childhood:
- ⅓of all pediatric malignancies
Histo:- Acute Lymphocytic Leukemia (ALL in 75%)
most often in children <5 years of age
- lymph node enlargement rare
- Acute Myelogenous Leukemia (AML)
tends to affect older children + adolescents
- lymph node enlargement common
- migratory paraarticular arthralgias (25–50%) ← adjacent metaphyseal lesions (may be confused with acute rheumatic fever / rheumatoid arthritis)
- low-grade fever, bruising, fatigue
- bone pain ← increased intraosseous pressure from proliferation of malignant cells
- elevated erythrocyte sedimentation rate, anemia
- hepatosplenomegaly, occasionally lymphadenopathy
◊Peripheral blood smears may be negative in aleukemic form!
Skeletal manifestations in 50–90%:
- Location: proximal + distal metaphyses of long bones, flat bones, spine
- Diffuse osteopenia (most common pattern)
- diffuse demineralization of spine + long bones ← leukemic infiltration of bone marrow + catabolic protein / mineral metabolism
- coarse trabeculation of spongiosa ← destruction of finer trabeculae
- multiple biconcave / partially collapsed vertebrae (14%)
- “Leukemic lines” (40–53% in ALL):
- transverse radiolucent metaphyseal bands, uniform + regular across the width of metaphysis (= leukemic infiltration of bone marrow / osteoporosis at sites of rapid growth)
Location: large joints (proximal tibia, distal femur, proximal humerus, distal radius + ulna)
- horizontal / curvilinear bands in vertebral bodies + edges of iliac crest
- dense metaphyseal lines after treatment
- Focal destruction of flat / tubular bones:
- multiple small clearly defined ovoid / spheroid osteolytic lesions (destruction of spongiosa, later cortex) in 30–60%
- moth-eaten appearance, sutural widening, prominent convolutional markings of skull
◊Lytic lesions distal to knee / elbow in children are suggestive of leukemia (rather than metastases)! - Isolated periostitis of long bones (infrequent):
- smooth / lamellated / sunburst pattern of periosteal reaction (= cortical penetration by sheets of leukemic cells into subperiosteum) in 12–25%
- Metaphyseal osteosclerosis + focal osteoblastic lesion (very rare)
- osteosclerotic lesions ← reactive osteoblastic proliferation (late in disease)
- mixed (lytic + bone-forming) lesions in 18%
Dx: sternal marrow / peripheral blood smear
Cx: proliferation of leukemic cells in marrow leads to extraskeletal hematopoiesis
DDx: metastatic neuroblastoma, Langerhans cell histiocytosis
- ADULTHOOD
- Death usually occurs before skeletal abnormalities manifest
- osteoporosis
- solitary radiolucent foci (vertebral collapse)
- permeating radiolucent mottling (proximal humerus)
MR:
- diffuse decrease in SI compared with normal marrow on T1WI
- isointense / mildly hyperintense compared with normal marrow on T2WI ← high water content of leukemic cells + displacement of fat
- abnormally hyperintense relative to normal marrow on STIR