Rib Lesion

Christopher G. Anton, MD

DIFFERENTIAL DIAGNOSIS

Common

Normal Variant
Healing Rib Fracture

Less Common

Enchondroma
Osteochondroma
Metastasis
Osteomyelitis
Fibrous Dysplasia
Langerhans Cell Histiocytosis
Osteoblastoma

Rare but Important

Ewing Sarcoma
Aneurysmal Bone Cyst
Lymphoma/Leukemia

ESSENTIAL INFORMATION

Key Differential Diagnosis Issues

If palpable chest wall mass, image with chest radiograph 1st, ± rib radiographs
- Asymmetric costochondral cartilage, congenital fused or bifid anterior rib
- Many have characteristic diagnostic features and need no additional imaging

Helpful Clues for Common Diagnoses

Normal Variant
- Bifid or fused ribs
- Relatively common, up to 3% of population (supernumerary > agenesis/aplasia > errors of segmentation)
- May present with firm or hard anterior chest wall mass
- Chest radiograph is diagnostic
Healing Rib Fracture
- Should be differentiated from pathologic fracture
- If multiple posterior rib fractures, nonaccidental trauma should be excluded

Helpful Clues for Less Common Diagnoses

Enchondroma
- Age: 15-40 years old
- Lytic, well-defined with chondroid matrix, endosteal scalloping, marginal sclerosis, no periosteal reaction or soft tissue mass
- Most commonly small tubular bones of hands and feet
- Ollier disease
  - Nonhereditary
  - More common in boys
  - Multiple enchondromas
  - Mostly unilateral, predilection for appendicular skeleton
  - Sarcomatous transformation (5%)
- Maffucci syndrome
  - Nonhereditary
  - Multiple enchondroma and soft tissue venous malformation
  - Unilateral involvement of hands and feet
  - Malignant transformation (15-25%)
Osteochondroma
- Age: 10-25 years old
- Most commonly around knee (35%)
- Metaphysis of long bones (70%)
- Pedunculated or sessile; grows away from joint
- Multiple hereditary exostoses
- Cartilage cap thickness is variable during childhood
- Malignant degeneration
  - 1% in solitary
  - 3-5% in multiple hereditary exostoses
  - Should consider if rapid growth, indistinct lesion margin, osseous destruction, &/or soft tissue mass
Metastasis
- Most commonly neuroblastoma
- Lymphoma/leukemia
  - More commonly metastatic than primary involvement
- Usually known malignancy
Osteomyelitis
- Over 50% occur in preschool age children
- Staphylococcus aureus most common pathogen for osteomyelitis in children (followed by Streptococcal pneumonia, Streptococcal pyogenes)
  - Most common pathogen in neonates
- If more aggressive infection present, also consider actinomycosis (especially after dental procedures)
  - Aspiration of saliva
  - Pulmonary infiltrate/mass may spread to pleura, pericardium, chest wall
- MRSA &/or ORSA becoming common cause of osteomyelitis
- Chronic recurrent multifocal osteomyelitis (CRMO)
  - Unknown pathogen; not bacterial infection
  - Metaphyseal lesion but can occur anywhere
  - Pustulous dermatosis (psoriasis, acne, palmar or plantar pustulosis)
  - Pustulous dermatosis occurs in children/adolescents (25%) and adults (50%) with CRMO
Fibrous Dysplasia
- Monostotic or polyostotic
- Expansile, endosteal scalloping, lucent to ground-glass appearance
- Sarcomatous degeneration in up to 0.5%
- McCune-Albright: Female, precocious puberty, café au lait spots, and unilateral fibrous dysplasia
Langerhans Cell Histiocytosis
- Flat bones (70%)
- Monostotic (50-75%)
- Well-defined or ill-defined margin, lytic ± sclerotic margin
- Beveled edges in skull
Osteoblastoma
- Benign osseous lesion with osteoid production
- Age: 10-20 years old
- > 1.5 cm (range 1-10 cm)
- Most commonly located in posterior elements of spine
- Expansile, lytic, cortex usually preserved ± internal calcification
- May present with painful scoliosis

Helpful Clues for Rare Diagnoses

Ewing Sarcoma
- Age: 10-25 years old
  - 90% before age 20 years
  - Caucasians (96%)
- Soft tissue or bone
- Slight male predominance
- Diaphysis of long bones (70%)
- Ill-defined, lytic, permeative, moth-eaten, large, soft tissue mass; aggressive periosteal reaction (“onion skin,” “sunburst”)
- Fever, leukocytosis, elevated ESR, soft tissue mass, localized pain
- Other sarcomas
  - Ewing family of tumors, synovial cell sarcoma, chondrosarcoma, osteosarcoma, malignant peripheral nerve sheath tumor, primitive neuroectodermal tumor
  - Chest wall tumor ± rib involvement
Aneurysmal Bone Cyst
- Expansile
- Septated with fluid-fluid levels (CT or MR) ± periosteal reaction
- Can present with pain and swelling
- Often associated with other benign tumors
Lymphoma/Leukemia
- Usually disseminated disease