Bone and Soft Tissue Tumors

Bone Tumors: Basics & Benign - Gentle Giants

• Approach: Age, location (epiphysis, metaphysis, diaphysis), margins (Lodwick: geographic IA/IB = benign; IC/moth-eaten/permeative = aggressive), matrix (osteoid, chondroid, fibrous), periosteal reaction (solid = benign; lamellated, sunburst, Codman = aggressive).
• Common Benign Tumors:
  • Osteochondroma: Most common. Metaphyseal, cartilage-capped exostosis.
  • Giant Cell Tumor (GCT): Epiphyseal, lytic, "soap bubble". Locally aggressive.
  • Enchondroma: Medullary cartilage lesion. Hands/feet.
  • Fibrous Dysplasia: Ground-glass matrix.
  • Non-Ossifying Fibroma (NOF): Eccentric, lytic, sclerotic rim.
  • Aneurysmal Bone Cyst (ABC): Expansile, fluid-fluid levels.

⭐ Osteochondroma is the most common benign bone tumor, typically presenting as a painless mass in adolescents.

Malignant Bone Tumors: Part 1 - Bad to the Bone

• Osteosarcoma (OS)
  • Most common primary bone malignancy (excl. myeloma). Pain, swelling.
  • Age: Peak 10-20 yrs; also >65 yrs (secondary: Paget's, radiation).
  • Site: Metaphysis (distal femur, prox. tibia/humerus).
  • X-ray: Sunburst, Codman's triangle, cloud-like osteoid.
• Ewing Sarcoma (ES)
  • Aggressive small round blue cell tumor; 2nd common in children.
  • Age: Peak 10-20 yrs.
  • Site: Diaphysis (long bones like femur), flat bones (pelvis).
  • X-ray: Onion-skin periostitis, moth-eaten destruction, large soft tissue mass.
  • Genetics: t(11;22) EWS-FLI1. 📌 "EWING t(11;22)"

⭐ Ewing Sarcoma often presents with systemic symptoms (fever, weight loss, ↑ESR), mimicking osteomyelitis.

Malignant Bone Tumors: Part 2 & Staging - More Meanies & Mapping

• Chondrosarcoma:
  • Malignant cartilage. Age: >40 yrs.
  • Sites: Pelvis, femur, ribs.
  • X-ray: "Rings & arcs", popcorn calcification.
  • 
• Multiple Myeloma (MM):
  • Commonest primary bone malignancy. Age: >50 yrs.
  • X-ray: "Punched-out" lytic lesions, vertebra plana.
  • 📌 CRAB: HyperCalcemia, Renal failure, Anemia, Bone lesions.
  • 
• Adamantinoma:
  • Rare, low-grade. Site: Tibial diaphysis.
  • X-ray: "Soap bubble" appearance.
• Staging: Enneking system (Grade, Site, Metastasis) guides therapy.

Key Malignant Bone Tumors Comparison:

Soft Tissue Tumors & Mimics - Beyond the Bone

• Soft Tissue Tumors (Key Examples):
  • Lipoma: Benign. Pure fat signal (T1/T2 hyper, fat-sats). Thin, few septa.
  • Liposarcoma: Malignant. Thick septa (>2 mm), nodular non-fatty areas, enhancement.
    • Well-differentiated: Often large, deep-seated.
    • Myxoid Liposarcoma: T2 hyperintense (myxoid stroma), "pseudocapsule", characteristic enhancement.
  • Synovial Sarcoma: Juxta-articular, young adults (15-40 yrs), calcification (~30%), "triple sign".
  • MPNST (Malignant Peripheral Nerve Sheath Tumor): NF1 association. Spindle cell tumor.
• Common Tumor Mimics (Bone & Soft Tissue):
  • Non-Ossifying Fibroma (NOF): Eccentric, cortically-based lucency, sclerotic rim, "bubbly". Self-resolves.
  • Fibrous Dysplasia: "Ground-glass" matrix, expansile.
  • Myositis Ossificans: Zonal ossification, peripheral maturation. Early phase can mimic sarcoma.
  • Hematoma: Signal varies with age. No true enhancement of collection.
  • Abscess: Rim-enhancing collection, surrounding inflammation.

⭐ A key differentiator for liposarcoma vs. lipoma on MRI is the presence of thick septa (>2 mm), nodular or globular non-adipose components, and enhancement of these non-fatty areas.

High‑Yield Points - ⚡ Biggest Takeaways

• Osteochondroma: Most common benign bone tumor.
• Multiple Myeloma: Most common primary malignant bone tumor overall.
• Osteosarcoma: Most common non-hematopoietic primary malignant bone tumor; metaphyseal, Codman's triangle, sunburst spiculation.
• Ewing's Sarcoma: Diaphyseal, t(11;22), onion-peel reaction, small round blue cell tumor.
• Giant Cell Tumor (GCT): Epiphyseal in skeletally mature patients, soap bubble appearance.
• MRI is crucial for soft tissue sarcoma staging; Liposarcoma is most common in adults.