Benign Bone Tumors

Tibia or Not Tibia, That is The Question

Bone to Be Wild

Osteo-Introductions (Benign Bone Tumors Describe Themselves)

Radiology Isn't Black or White (Imaging)

Bad to the Bone

100

A 24-year-old male presents to the clinic complaining of right leg pain. He states the pain is worse at night, but does improve after taking Advil. On X-ray, you see a radiolucent nidus with a ring of surrounding sclerotic woven bone in the cortex of the femur. The lesion measures < 2 cm. This most likely represents an...

a. Osteoid osteoma

b. Osteoblastoma

a. Osteoid osteoma

Explanation

Osteoid osteomas:

< 2 cm (Mnemonic: "Big Blast," Osteoid is a shorter word than osteoblastoma)

Improve w/ NSAID use

Often occur in surface of cortex/diaphysis of long bones

Thick sclerotic rim (Imagine concentric Os; outer sclerotic ring is capital O, nidus ring is lowercase o)

Affects < 25 years old

100

A 35-year-old male presents to the clinic with pain in the third metacarpal bone of his right hand. X-ray reveals a radiolucent lesion in the medullary cavity of the third metacarpal bone. The lesion appears to have a "rings and arcs" appearance on X-ray. This most likely represents which benign bone tumor?

a. Enchondroma

b. Osteochondroma

a. Enchondroma

Explanation:

Typically affect those in the first through fourth decades of life

"Rings and arcs"/endosteal scalloping on imaging

Typically present in medulla of hands/feet but can occur in long bones

100

My stromal tumor cells overexpress RANK-L; this causes the creation of large osteoclastic cells with multiple nuclei. Some people call me an osteoclastoma. What am I?

Giant cell tumors

Explanation:

Osteoclasts express RANK and are activated by the overexpression of RANKL by stromal cells. Osteoclastic activity causes destruction of surrounding bone.

100

This imaging finding is suggestive of a benign bone tumor called a...

Giant cell tumor

Explanation

Endosteal scalloping results in ridges on the endosteum; resulting in the "soap bubble appearance"

100

You're a pathologist examining a sample of a benign bone tumor under the microscope. This sample came from the medulla of the femur of a 14-year-old boy. On examination, you see intermittent trabeculae surrounded by fibrous tissue. An image is shown below (b = bone and ft = fibrous tissue). This most likely represents:

a. Simple bone cyst

b. Endochondroma

c. Fibrous dysplasia

d. Osteoid osteoma

c. Fibrous dysplasia

Explanation

Fibrous dysplasia:

Woven bone surrounded by fibroblasts

Often occurs in early adolescence; stops after growth plate closes

Often occurs in medulla diaphysis of long bones

200

A 14-year-old male presents to the clinic with back pain. He states his back pain does not improve even after taking Ibuprofen. X-ray of his lumbar spine reveals a 3.5 cm lesion w/ cortical expansion and a thin rim of surrounding sclerosis. This most likely represents a(n)...

a. Osteoid osteoma

b. Osteoblastoma

c. Osteochondroma

d. Giant cell tumor

b. Osteoblasteoma

Explanation:

Osteoblastomas are:

> 2 cm (Mnemonic "Big Blast" or Osteoblastoma is longer word than osteoid)

Cortical expansion and surrounding rim of sclerosis sometimes seen; however, osteoid osteoma will have a thicker sclerotic rim

Unresponsive to NSAIDs (Mnemonic, unlikely to treat pain from blast/explosion with Advil)

Most cases occur in those 10-30 years old; peak incidence in 20s

Typically occur in axial spine (Mnemonic: osteoblastoma has a lowercase l, the axial spine is linear(ish)

200

An 11-year-old boy is brought to the office by his parents with a 2-month history of progressive swelling of his right upper arm. He has otherwise been healthy. Medical history is unremarkable and he takes no medications. Immunizations are up-to-date. He appears well-nourished and well-developed. He is at the 60th percentile for height and weight. Vital signs are within normal limits. Physical examination reveals an immobile mass on the right proximal humerus that is nontender to palpation. Laboratory studies reveal an erythrocyte sedimentation rate of 10 mm/h (reference range: 0–15 mm/h) and an alkaline phosphatase of 35 U/L (reference range: 25–100 U/L). A radiograph of the right humerus reveals a 3-cm sessile bony protrusion with a cartilage cap on the proximal metaphysis. Which of the following is the most likely diagnosis?

a. Osteoid osteoma

b. Osteochondroma

c. Osteosarcoma

d. Chondroblastoma

e. Ewing Sarcoma

f. Chondrosarcoma

b. Osteochondroma

Explanation:

< 25

Cartilage cap

Grows on long bones out of growth plate, found typically foud on metaphysis

Can be sesslie (flatter) or pedunculated (mushroom-like)

200

Hi! I typically grow on the surface of facial bones. I'm associated with Gardner Syndrome (which occurs due to a mutation in the APC gene). What am I?

a. Osteochondroma

b. Endochondroma

c. Osteoma

d. Osteoid osteoma

e. Osteoblastoma

c. Osteoma

Explanation:

Osteomas are a symptom of Gardner Syndrome, a familial adenomatous polyposis disease

APC (adenomatous polyposis coli) is a tumor suppressor gene

200

This benign bone tumor that typically grows from the metaphysis of bones and has a distinctive appearance (shown below). It's is called a(n)...

a. Osteosarcoma

b. Endochondroma

c. Chondrosarcoma

d. Osteochondroma

Explanation

Osteochondromas:

Typically appear in adolescence

Grow from the metaphysis of long bones (near the growth plate)

Have a “pedunculated” (mushroom-like) appearance on imaging

Have a cartilage cap

200

A 12-year-old patient presents to the clinic with his mother complaining of pain in his left arm after stumbling into a tree. Surprisingly, X-ray reveals a fracture to the metaphysis of his proximal humerus at well as fibrous-lined fluid filled spaces at the site of the fracture. This most likely represents:

a. Osteoblastoma

b. Endochondroma

c. Unicameral bone cyst

d. Chondroma

c. Unicameral bone cyst

Explanation

Unicameral bone cysts:

Often occur in metaphysis

Fluid-filled space; fibrous lining

Can lead to pathologic fractures

Typically occur in those <20

300

Based on appearance on X-ray, this benign bone lesions is likely an...?

a. Osteoblastoma

b. Osteoid osteoma

Explanation:

Osteoid osteomas typically present in the cortex/diaphysis of long bones

Thick sclerotic rim (Mnemonic: imagine concentric Os; outer sclerotic ring is capital O, nidus ring is lowercase o)

300

This imaging finding is suggestive of...

a. Osteochondroma

b. Enchondroma

Explanation:

"Rings and arcs" appearance on X-ray

300

I'm > 2 cm. I usually present in the spine, but sometimes I present in long bones. Here's a selfie. What am I?

a. Giant cell tumor

b. Enchondroma

c. Osteoblastoma

d. Osteoid osteoma

c. Osteoblastoma

Explanation

Osteoblastomas are:

> 2 cm (Mnemonic "Big Blast" or Osteoblastoma is longer word than osteoid)

Typically occur in axial spine (Mnemonic: osteoblastoma has a lowercase l, the axial spine is linear(ish)

300

This benign tumor can occur after trauma. The imaging below is most suggestive of:

a. Myositis ossificans

b. Enchondroma

c. Osteoid osteoma

d. Osteoma

e. Osteoblastoma

a. Myositis ossificans

Explanation

Myositis ossificans:

Bone growth in muscle

Example of "hetertropic ossification"

Can occur several months after blunt trauma to muscle

Common in larger muscles (e.g. quadriceps, brachialis, etc)

"Eggshell calcification" on imaging

Painful mass of soft tissue

300

A 20-year-old female semi-professional softball player presents to her PCP after noticing a painful lump on her quadriceps 1 week prior. When asked what she thinks caused her injury, she states she is unsure; however, she notes that she was struck in the thigh by a very fast softball pitch approximately 3 months prior. On X-ray, you note a soft tissue mass with eggshell calcification; on histology, you see zonal architecture and fibroblastic proliferation surrounded by metaplastic bone formation. Her diagnosis most likely represents:

a. Fibrous dysplasia

b. Chondroma

c. Endochondroma

d. Myositis ossificans

Explanation

Myositis ossificans:

Bone growth in muscle

Manifests as painful mass of soft tissue

Common in larger muscles (e.g. quadriceps, brachialis, etc)

Example of "heterotropic ossification"

Can occur several months after blunt trauma to muscle

"Eggshell calcification" on imaging

Fibroblasts seen on histology slides because bone is formed from cartilage

"Zonal architecture" refers to the concentric circles seen on imaging/histo; these distinct zones correspond to the different stages of bone growth

400

A 22-year-old male presents to his PCP complaining of right arm pain. He states he doesn't believe in western medicine, so he's unsure whether NSAIDs improve his pain. On X-ray, you see a lesion in his radius, but the computer you're using to view the X-ray shuts down for a required update before you get a proper look at it. Based on the location of the lesion, this is most likely an...

a. Osteoblastoma

b. Osteoid osteoma

Explanation

Osteoid osteomas:

Occur more frequently in the appendicular spine; osteoblastomas favor the axial spine