Medicine

Benign Bone Tumors

A concise overview of benign active bone tumors. They include osteoid osteoma, fibrous cortical defects, osteochondroma, enchondroma and unicameral or solitary bone cysts.
 

These can be classified into:

  • Bone forming lesions
  • Fibrous lesions
  • Cystic Lesions

Bone Forming lesions

Osteoid Osteoma

This tumor arises from osteoblasts and peak in the 2nd and 3rd decades of life. Males are affected twice as much as females. The Proximal Femur and Tibial Diaphysis are the most common places for this tumor to occur.

It is not known to metastasize.

On radiography, you'll appreciate:

  • small round radiolucent nidus less than 1.5 cm, surrounded by dense sclerotic bone. *Remember Bulls Eye*

Osteoid Osteoma



Osteoid Osteoma



Symptoms

Produces severe intermittent pain from prostaglandin secretion and COX 1/2 expression, mostly at night (diurnal prostaglandin production). This is therefore chracteristically relived by NSAIDs

Aspirin's (NSAIDs) ability to suppress the production of prostaglandins and thromboxanes is due to its irreversible inactivation of the cyclooxygenase (COX) enzyme. Cyclooxygenase is required for prostaglandin and thromboxane synthesis.

Treatment

NSAIDs for night pain with surgical resection of the nidus.

Fibrous Lesions

Fibrous Cortical Defect

This is also called a non-ossifying fibroma or fibrous bone lesion. It is the most common benign bone tumor in children. They are typically asymptomatic and incidental.

They occur in about 35% of children peaking at 2-25 years old. Males have a higher prevalence.

The most common locations are the proximal tibia and femur. 50% of patients have multiple lesions, which are usually symmetrical and bilateral.

Radiographic Findings

  • These findings are diagnostic. You may see a metaphyseal "bubbly" lytic lesion near the physis, it is think and smooth, lobulated with a well defined sclerotic margin.

Treatment

Most resolve spontaneously

Fibrous Cortical Defect



Fibrous Cortical Defect



Osteochondroma

This is a cartilage capped bony tumor and occurs typically in the 2nd and 3rd decades of life. Males are affected 1.8 times more than females.

It is the most common of all the benign bone tumors overall at 45%.

Its classified into:

  • Sessile (sesame seed or island like) - broad based and has an increased risk of malignant degeneration

Sessile Osteochondroma



  • pedunculated (attached to a peduncle/narrow stalk). See image below

They occur in:

  • The metaphysis of long bone near the tendon attachment site (usually distal femur, proximal tibia or proximal humerus)

Radiographic findings

  • Cartilage capped bony spur on the surface of the bone (mushroom on xray)

Osteochondroma



They may be multiple (its hereditary autosomal-dominant form), and these are associated with a higher risk of malignant change.

Symptoms

Generally slow growing and asymptomatic unless impinging on neurovascular structures ("painless masses") and stops growing when the skeleton matures.

Overall, malignant change occurs in 1-2% of cases and suspect if lesion becomes painful or rapid growth observed.

Treatment

Observe. Surgical excision indicated if symptomatic.

Enchondroma

This is a tumor of the hyaline cartilage, benign and involves abnormal chondroblasts, where the majority are asymptomatic and presents as an accidental finding or pathological fracture.

It occurs in the second and third decades of life. They are found in:

  • 60% - small tubular bones of the hand and foot
  • 20% - femur
  • remaining - humerus and ribs

It develops on the medullary cavity. They appear on xray as:

  • single/multiple enlarged areas that are rarefied (less dense) and found in tubular bone
  • lytic lesions with sharp margin and irregular calcification (stippled,punctate or popcorn appearance)

Enchondroma



Enchondroma



Malignant degeneration can occur in 1-2% (look for pain in the absence of fracture). Not known to metastasize.

Treatment

Observe with serial x-rays, Surgical curettage if symptomatic or if lesion grows.

Cystic Lesions

A unicameral/solitary bone cyst. (Unicameral = single chamber) is the most common cystic lesion and is filled with serous fluid.

Occurs in children and young adults, peaking in the first 2 decades of life. Males are twice as likely as females.

The most common locations are the proximal humerus and femur.

Symptoms/Presentation

  • Asymptomatic or local pain. Incidental detection
  • Complete pathological fracture (50% of presentation)

Radiography

  • Lytic or translucent area on metaphyseal side of growth plate.
  • Cortex thinned and expanded.
  • Lesion is well defined

Treatment

Aspiration followed by steroids, with curettage and bone graft if refracture is likely.

Unicameral Bone Cyst



Unicameral Bone Cyst