What are the other Names for this Condition? (Also known as/Synonyms)

• Benign Fat Tumor of Bone
• Bone Lipoma
• Intraosseous Lipoma

What is Lipoma of Bone? (Definition/Background Information)

• Lipoma of Bone is a rare benign tumor. It is considered by some to be one of the rarest, benign, primary tumors of bone
• These benign tumors are composed of adipose (body fat) tissue and can arise, either from the bone marrow cavity (called intramedullary lipomas), or from just below the bone surface (called sub-periosteal lipomas)
• Commonly, a Bone Lipoma affects the bones of the feet, skull, jaw bones, forearm, ribs, and long bones of the legs
• A diagnosis is suspected on a radiological study of the affected region, and the condition can be confirmed on a tissue biopsy of the tumor
• Both conservative and surgical methods are available to treat Lipomas of Bone. A surgery can bring about a complete cure with excellent prognosis 

Who gets Lipoma of Bone? (Age and Sex Distribution)

• It is estimated that 1 in 1000 tumors of the bone are Bone Lipomas
• The average age of individuals, who are affected is 43 years; though, the tumor may occur at any age
• There is no known gender, racial, or ethnic preference 

What are the Risk Factors for Lipoma of Bone? (Predisposing Factors)

Currently, no risk factors are noted for the development of Lipoma of Bone. 

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases ones chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others. 

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider. 

What are the Causes of Lipoma of Bone? (Etiology)

The exact cause and mechanism of formation of Lipoma of Bone, is unknown. 

What are the Signs and Symptoms of Lipoma of Bone?

The signs and symptoms of Lipoma of Bone include:

• When present, pain in the affected bone is the most common symptom; otherwise, the tumors are usually asymptomatic
• Often, the tumor is painless and is found incidentally on radiological studies, which is performed for some other health issue/condition
• A Lipoma of Bone can occur as a single tumor (solitary Lipoma of Bone) or as multiple tumors (multiple Lipomas of Bone)
• Frequently, the benign tumor affects the bones of the foot (calcaneus bone), skull, jaw bones (mandible), forearm (ulna), ribs, and long bones of the leg, such as the femur, fibula, and tibia
• Very rarely, large tumors may weaken the bone resulting in fractures (pathological bone fractures), which can be the main reason for seeking treatment 

How is Lipoma of Bone Diagnosed?

The diagnostic tests may vary, based on the location of the tumor. A diagnosis of Lipoma of Bone may involve:

• Physical examination, evaluation of the individual’s medical history
• X-ray, CT scan, or MRI scan of the affected region, to aid in obtaining a clear image of the tumor
• Tissue biopsy of the tumor - the specimen is examined under a microscope by a pathologist, to arrive at a definitive diagnosis
• Due to the rarity of the tumor, it is often misdiagnosed 

“Based on the radiological CT/MRI features, Milgram and co-workers proposed 3 categories of Bone Lipomas:

• Type 1: Sharply delineated, viable lipomas with homogeneous fat content
• Type 2: Predominantly fatty lesions with central necrosis, calcifications or ossifications
• Type 3: Heterogeneous, fat-containing lesions with multiple necrosis, cystic transformations, wall sclerosis, and extensive calcifications or ossifications.”

The above classification helps the healthcare provider in planning the next treatment steps. 

(Source: Intraosseous lipomas: radiologic and pathologic manifestations by J W Milgram; and Intraosseous lipoma by Dr Ayush Goel and Dr Roberto Schubert et al. Radiopaedia.org) 

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis. 

What are the possible Complications of Lipoma of Bone?

Complications due to Lipoma of Bone could include:

• Pathological fracture of a bone (fracture due to bone weakness), if the tumor is large
• In some rare cases, Lipoma of Bone may undergo malignant transformations, to form a malignant osteosarcoma. These transformations may occur sporadically 

How is Lipoma of Bone Treated?

The treatment of Lipoma of Bone is undertaken as:

• Conservative treatment is the treatment of choice for lipoma tumors that do not affect bone stability. Conservative methods include close observation and follow-up
• Complete surgical excision of the tumor is curative. Surgical intervention with complete excision, not only results in a complete cure, but also eliminates the chances of tumor recurrence
• In case of large tumors causing bone stability issues, with prominent symptoms, or showing features of concern on radiological images, they can be removed by surgical curettage of the tumor. The surgical curettage may be followed by bone grafting, if needed
• In some rare cases, bones need to be stabilized to increase bone strength. In such cases, certain bone stabilization procedures may be used. Common bone stabilizing procedures include internal fixation and intramedullary rodding 

How can Lipoma of Bone be Prevented?

• Current medical research has not established a way of preventing Lipoma of Bone
• Regular medical screening at periodic intervals with scans and physical examinations are important 

What is the Prognosis of Lipoma of Bone? (Outcomes/Resolutions)

• With a majority of Bone Lipomas, only conservative treatment is necessary
• In some cases, a surgery may be required. In these individuals, the prognosis of Lipoma of Bone is excellent with surgical intervention.
• A complete removal of the tumor is preferred, to prevent the tumor from recurring 

Additional and Relevant Useful Information for Lipoma of Bone:

Since, many bone tumors and conditions have similar appearance to Bone Lipomas on radiological studies, a differential diagnosis must be considered. Some of these tumors and conditions include:

• Non-ossifying fibroma of bone
• Aneurysmal bone cyst (ABC)
• Chondrosarcoma
• Fibrous dysplasia of bone
• Simple bone cysts (unicameral bone cyst)
• Bone infarctions