L16. Benign Tumors of the Musculoskeletal System

Characteristics of benign tumors

- Well-defined geographic lesion on radiology
- Shape smooth/oval
- No skin dimpling
- The patient is frequently asymptomatic
- Capsulated
- Slow growing

Characteristics of malignant tumors

- Lytic lesion with poor defined margins
- Irregular shape/not smooth
- Skin dimpling
- Painful
- Fast growing
- Non-capsulated

Lytic lesions

- These are spots of bone damage that result from cancerous plasma cells building up in your bone marrow

Questions to ask in a patient's workup

- Habits: like smoking
- Duration of complaint: benign may be there for years while malignant is for weeks/months
- Rate of growth
- Personal or family history of cancer: may increase odds of malignant lesions
- Systemic signs: weight loos, sweats, malaise, fever

Osteochondromas

- Most common benign bone tumor usually found in patients aged 10-20
- X-rays will show a bony outgrowth from the cortex (which is unique)

Hereditary multiple osteochondromatosis

- An autosomal dominant condition that can lead to both sessile and pedunculate lesions
- The risk of these osteochondromas turning into chondrosarcoma is 25-30% in patients with this disease

Treatment of Osteochondroma

- Excision or other treatment is needed if the tumor is hindering the patient's quality of life
- Tumors near a nerve, that causes pain disturbs growth, or appearance on x-ray suggests transformation into malignant chondrosarcoma may require excision of the tumor

Fibrous dysplasia

- This type of benign tumor involves a skeletal developmental problems
- In this condition, the medullary bone is replaced by fibrous tissue which appears radiolucent on radiographs, with the classically described ground-glass appearance
- Trabeculae of woven bone contain fluid-filled cysts that are embedded largely in collagenous fibrous matrix, which contributes to the generalized hazy appearance of the bone

Monostotic fibrous dysplasia

- This type of fibrous dysplasia is 7-10 times more common than polyostotic fibrous dysplasia
- Can also be associated with systemic conditions like precocious puberty and skin pigmentation and soft tissue myxomas

Imaging of Fibrous Dysplasia

- Plain radiographs will show expansion of the metaphysics and diaphysis, endosteal scalloping, and group glass appearance of the matrix
- A CT scan will show an expanding intramedullary lesion

Treatment of Fibrous Dysplasia

- Conservative and primarily to prevent deformity
- Early evidence suggests that vitamin D and bisphosphonates (after physical closure) may be helpful in ameliorating pain and possibly in reconstituting lesions with normal bone
- Concomitant calcium (500-1500 mg/day) and vitamin D2 (800-1200 IU/day) must be given to avoid secondary hyperparathyroidism

Surgical indications for treatment of Fibrous dysplasia

- Severe or progressive disease
- Persistent pain
- Fracture of a weight bearing bone
- Deformity of the bone may require corrective osteotomy and internal fixation

Chondroma

- This type of benign bone tumor predominantly in men who are in their 2nd to 4th decades
- Tumors are usually asymptomatic but may enlarge and become painful
- Often found when x-rays are taken for another reason
- On x-rays the tumors may appear lytic with areas of stippled calcification
- Mostly in the small bones of the hand and/or feet

Treatment of chondromas

- X-ray findings may be diagnostic, if they are not, or if the tumor is painful, the diagnosis should be confirmed by biopsy
- An asymptomatic patient does not need excision or other treatment, however, follow-up c-rays are indicated to rule out disease progression

Non-ossifying fibroma (NOF)

- This is a well circumscribed, solitary fibrous proliferation
- Lesion is found mostly in children with 75% occurring in the second decade
- A non-neoplastic process that occurs in the juxaepiphyseal region of the long bones
- Most common site is the femur followed by the tibia
- Asymptomatic and usually discovered as an incidental finding on x-ray

Imaging of non-ossifying fibroma

- Tumors are eccentric, multi-loculated sub-cortical lesion with a central lucency and a scalloped sclerotic margin
- Sometimes cortical thinning is present but no periosteal reaction

Treatment of non-ossifying fibroma

- Lesions normally regress spontaneously
- The only definite indication to treat is if there is a pathologic fracture

Chondroblastoma

- Also known as Codman's tumor
- A rare benign bone tumor that originates from cartilage
- Most often affects the ends of the long bones in the arms and legs
- Occurs most commonly in people aged 10-20

Imaging of chondroblastoma

- X-ray will show a cyst like mass containing spots of calcification
- Lesions are lytic with well defined margins
- Contains fine calcifications, either punctuate or in rings, may be visible
- Using a CT is also helpful for defining the relationship of the tumor to the joint, integrity of the cortex, and intralesional calcifications

Symptoms of chondroblastoma

- They can vary depending on where the tumor is located
- Pain in the hip, knee, and shoulder joint
- Withered or shrunken appearance of the muscle near the affected bone
- Fluid accumulation in the joint adjacent to the affected bone

Treatment of chondroblastoma

- Surgical removal of the tumor
- Bone grafting
- Physical therapy
- The tumor may recur so follow-up is required

Chondromyxofibroma

- This is a very rare benign bone tumor that occurs before the age of 30
- lesions will appear eccentric, sharply circumscribed, well defined margins, and lytic on an x-ray
- Lesions usually has a sclerotic margin of bone
- Ridges and grooves will appear in the margins (this is unique)
- Treat by surgical excision or curettage

Osteoid Osteoma

- This type of benign bone tumor tends to affect young adults
- Most common benign osteoid-forming tumor
- Males have a greater chance than females
- Proximal femur is the most common site
- Causes dull aching pain that is generally worse at night
- Physical examination will reveal atrophy of regional muscles
- Symptoms will be relieved with non steroidal anti-inflammatory drugs (NSAIDs) secondary to a high concentration of prostaglandins

Imaging of osteoid osteoma

- X-rays will show a small radiolucent zone (called a nidus) surrounded by larger sclerotic zone
- If a tumor is suspected a technetium-99m bone scan should be performed and this tumor will appear as an area of increased uptake

Treatment of Osteoid osteoma

- NSAIDs can usually receive pain
- Permanent relief is obtained if the small radiolucent zone is removed surgically or with percutaneous readiofrequency ablation
- Surgery is not always the first option due to their extensiveness and that they may require resection of large areas of bone and implantation of bone grafts
- Can be treated with ablation where the tumor is heated up for 6 minutes and thus ablated. This is minimally invasive and can be done in an outpatient clinic

Benign giant cell tumor

- Most commonly affects people in their 20s and 30s
- They are known to recur
- Rarely they will metastasize, even though it remains histologically benign
- Patients may present with a visible mass, swelling, and bone fractures

Imaging of benign giant cell tumor

- There will be a well-defined defect in the metaphysics and epiphysis with destruction of the medullary cavity and adjacent cortex
- Destruction may stop just short of the joint

Treatment of benign giant cell tumor

- Curettage and packing
- Excision is rarely needed

Osteoblastoma

- This is a solitary, benign and self-limited tumor that produces osteoid and bone
- In the spine the tumor is usually located in the posterior process while he vertebral bodies are spared

Imaging of osteoblastoma

- X-ray will show a radio-lucent defect with a central density due to ossification
- Lesion is well circumscribed and may have surrounding sclerosis

Treatment for osteoblastoma

- Surgical resection by curettage, intralesional excision or en-bloc excision are all options depending on site of lesion
- Cryosurgery, radiation and chemotherapy may have a role in aggressive and surgically unresectable lesions of the spine

Enchondroma

- These are benign cartilage tumors that are commonly found in the tubular bones of the hand and foot
- Chondrocytes of enchondromas grow slowly, expanding the cortical bone and thinning the cortex
- May cause unsightly swelling or pathologic fracture of the bone
- Many will have no symptoms
- Hand pain may occur if the tumor is very large and there will be enlargement of the affected fingers
- On x-rays the lesions will appear radiopaque

Treatment for enchondroma

- Surgery: if the cone is weakened or fractures occur
- Bone grafting: where healthy bone is transplanted from another part of the patient's body into the affected area