Adamantinoma

Adamantinoma is a rare bone cancer. It's a tumor of long bones that most often develops in the shinbone, also called the tibia. It also may involve the fibula, another bone in the lower leg. Rarely, it develops in other long bones. One type of adamantinoma, called classic adamantinoma, often grows slowly. But it can return after treatment or spread to other parts of the body.

Long-bone adamantinoma is different from ameloblastoma. Ameloblastoma is a separate tumor that develops in the jaw.

Types

The main types of adamantinoma are classic adamantinoma, osteofibrous dysplasia-like adamantinoma and dedifferentiated adamantinoma. Osteofibrous dysplasia-like adamantinoma also may be called differentiated adamantinoma.

Classic adamantinoma

Classic adamantinoma is a cancerous bone tumor. This type can return where it started or spread to other parts of the body. It most often affects adults.

Osteofibrous dysplasia-like adamantinoma

An osteofibrous dysplasia-like adamantinoma has small groups of tumor cells scattered within tissue that resemble osteofibrous dysplasia. This is a separate bone condition.

Because the tumor cells are scattered, it can be hard to diagnose osteofibrous dysplasia-like adamantinoma. A small tissue sample taken in a biopsy may not contain these tumor cells, which can make diagnosis difficult. This type can return in the affected bone. Studies that have evaluated this type haven't reported spread to distant parts of the body. This type tends to be diagnosed at younger ages than classic adamantinoma.

Dedifferentiated adamantinoma

Dedifferentiated adamantinoma is very rare. Part of the tumor has cells with more-aggressive features under a microscope. This type also may act more aggressively than classic adamantinoma.

How adamantinoma differs from osteofibrous dysplasia

Osteofibrous dysplasia is different from adamantinoma because osteofibrous dysplasia is a separate bone tumor that isn't cancer. It usually starts in childhood.

Osteofibrous dysplasia, osteofibrous dysplasia-like adamantinoma and classic adamantinoma can look similar in imaging tests and tissue samples. But they have differences, and it's important to diagnose each of these specific conditions as each one may have different treatments and outlooks. Researchers continue to study how these three conditions are related. Studies haven't shown that osteofibrous dysplasia changes into classic adamantinoma. Depending on the quality of tissue samples used, the diagnosis may change from one to the other after more biopsies or tissue exams.

Adamantinoma symptoms may develop gradually. They can include:

• Pain in one area, often along the shin.
• Swelling near the affected bone.
• A lump or bulge over the affected bone.
• A limp or trouble putting weight on the affected leg.
• A break, also called a fracture, in a bone weakened by the tumor.
• Bowing or another change in the shape of the lower leg.

The way a lump looks or feels isn't enough to confirm adamantinoma. A lump can have many other causes. Imaging tests can show whether the lump involves bone. But a biopsy is needed to confirm that the lump is caused by adamantinoma.

Shin pain can have many causes, such as shin splints or a bone tumor. Symptoms alone don't give enough information to diagnose the cause.

When to seek care

Make an appointment with a healthcare professional if bone pain lasts, gets worse or happens at night. Also make an appointment if you have swelling or an unexplained lump over a bone. These symptoms can have many causes. Your healthcare professional may suggest imaging tests to find the cause.

The cause of adamantinoma isn't known. Researchers continue to study how the tumor starts and how adamantinoma may be related to osteofibrous dysplasia.

Studies have not shown that adamantinoma is inherited, meaning passed from a parent to a child.

Risk factors for adamantinoma aren't known. No proven link has been found between adamantinoma and exposure to chemicals, radiation or particular activities. Classic adamantinoma is most often diagnosed in young and middle-aged adults. Osteofibrous dysplasia-like adamantinoma tends to be diagnosed at younger ages, including in children and teens.

Studies don't consistently show that adamantinoma affects one sex more often.

Adamantinoma can weaken the affected bone and cause it to break. The tumor also may grow beyond the bone into nearby soft tissues. Classic adamantinoma can spread to other parts of the body, most often the lungs.

Care team

Care for adamantinoma generally involves a team with experience treating bone tumors. The team may include many specialists in the following areas.

• Orthopedic oncology.
• Musculoskeletal radiology.
• Bone pathology.
• Medical oncology.
• Radiation oncology.
• Rehabilitation.

Other specialists may be involved based on the tumor's location, whether it has spread and the treatment needed.

To diagnose adamantinoma, your healthcare professional will likely ask about your symptoms and your medical history and do a physical exam. Diagnosis also usually includes imaging tests and a biopsy. During a biopsy, a specialist removes a tissue sample for examination in a lab. A biopsy is needed to confirm adamantinoma.

Imaging tests

Imaging tests may include:

• X-ray. An X-ray is generally the first imaging test for a suspected primary bone tumor. A primary bone tumor is a tumor that starts in the bone. An X-ray can show the location of a bone lesion and changes in the affected bone.
• MRI. An MRI can show the tumor's size and how far it extends within the bone and nearby soft tissue. It also can help your care team plan a biopsy or surgery.
• CT. A CT scan gives detailed pictures of the bone. It can show changes in the hard outer layer of the affected bone. It also can help your care team plan a biopsy or surgery.
• Chest imaging. Chest imaging may be done to look for spread of classic adamantinoma to the lungs. The lungs are the most common area where classic adamantinoma spreads.

Biopsy and pathology

After imaging tests, your health professional takes a small tissue sample in a procedure called a biopsy. The tissue sample is usually removed with a needle. A doctor called a pathologist examines the sample under a microscope.

The team of specialists that will treat you usually plans the biopsy. Because the tumor can have different features in different areas, a small sample may not show all its features. Your care team reviews the imaging tests and biopsy results together.

Conditions that can look similar

Adamantinoma can look similar to other conditions on imaging tests or in small tissue samples. These conditions include osteofibrous dysplasia, fibrous dysplasia, low-grade central osteosarcoma and Ewing sarcoma. Your care team reviews imaging findings and biopsy results together to confirm your diagnosis.

Adamantinoma-like Ewing sarcoma is a rare type of Ewing sarcoma. This tumor most often develops in the head and neck. It is not a type of long-bone adamantinoma.

Adamantinoma treatment depends on the size and type of tumor, whether it has spread, and whether surgery can remove it completely. Surgery is usually the main treatment for classic adamantinoma. Your care team discusses treatment options with you.

Surgery

The goal of surgery is to remove the tumor in one piece along with a rim of surrounding tissue. The rim is called a surgical margin.

A margin without tumor cells is called a clear margin. It is linked to a lower risk of the cancer coming back in the same area, called local recurrence. When possible, the goal of surgery is to completely remove the tumor while keeping use of the limb.

If tumor cells are found in the margin, the risk of local recurrence is higher. Local recurrence is when the tumor returns in the treated area. It is different from metastasis. Metastasis means the tumor has spread to another part of the body.

Reconstruction after surgery

To remove the tumor, the care team may need to remove part of the affected bone. Rebuilding the bone may restore strength and help preserve use of the limb. Reconstruction may use a bone graft, an implant or another technique.

When amputation may be considered

Amputation is surgery to remove part or all of an arm or a leg. The care team may consider amputation when surgery can't completely remove the tumor and preserve use of a limb. Not everyone with adamantinoma needs amputation.

Chemotherapy and radiation therapy

Classic adamantinoma isn't routinely treated with chemotherapy or radiation therapy because there is little evidence to support their use. If a tumor can't be removed, returns or spreads, the care team chooses treatment based on the specific situation.

Possible complications of treatment

After surgery, the bone may heal slowly or may not heal completely. When a bone doesn't heal, this is called nonunion. Other possible complications include infection, a fracture of a bone graft or another reconstruction problem. You may need another procedure to treat these complications.

Follow-up care

Long-term follow-up is important because adamantinoma can return in the treated area or spread many years after treatment. Follow-up may include an exam, imaging of the treated area, chest imaging, and checks of the reconstruction and limb function. There is no single adamantinoma follow-up schedule. Talk with your care team about your follow-up schedule.

Prognosis

Several factors affect your outlook, also called prognosis. Outlook may depend on the tumor's type and location, whether it has spread or returned, and whether surgery achieved a clear margin.

Complete removal of localized adamantinoma may offer a chance of a cure. Long-term follow-up is still important because the tumor can return or spread years later.

Start by making an appointment with a healthcare professional if you have symptoms that worry you.

Here's some information to help you get ready for your appointment.

What you can do

When you make the appointment, ask if there's anything you need to do ahead of time, such as fasting before having a certain test. Make a list of:

• Your symptoms, including those that don't seem linked to the reason for your appointment, and when they began.
• Key personal information, including major stresses, recent life changes and family medical history.
• All medicines, vitamins or other supplements you take, including the doses.
• Questions to ask your healthcare team.

Bring a family member or friend with you, if possible, to help you remember the information you get.

Some basic questions to ask include:

• What's likely causing my symptoms?
• Other than the most likely cause, what are other possible causes for my symptoms?
• What tests do I need?
• What type of tumor do I have?
• What treatment do you recommend?
• I have other health conditions. How can I manage them together?
• Should I see a specialist?
• Are there brochures or other printed information I can have? What websites do you suggest?

For adamantinoma, some suggested questions may include:

• Has the tissue been reviewed by a bone tumor pathologist?
• Which type of adamantinoma is this?
• Can surgery preserve the limb?
• Will reconstruction be needed?
• How might each surgical option affect my movement and activity?
• Were the surgical margins clear?
• What long-term follow-up is recommended?

Be sure to ask all the questions you have.

What to expect from your care team

Your healthcare team is likely to ask you questions, such as:

• Do you have your symptoms all the time or do they come and go?
• How bad are your symptoms?
• What, if anything, seems to make your symptoms better?
• What, if anything, appears to make your symptoms worse?