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

• BPOP (Bizarre Parosteal Osteochondromatous Proliferation)
• Nora Lesion
• Nora’s Lesion

What is Bizarre Parosteal Osteochondromatous Proliferation? (Definition/Background Information)

• Bizarre Parosteal Osteochondromatous Proliferation (BPOP) is an uncommon, benign bone tumor that grows outward affecting the bone cartilage and cortex (the surface of the bone). Even though benign, BPOP is generally painful and exhibits rapid growth and local aggression. The tumor is also referred to as Nora’s Lesion
• It can affect individuals of a wide age group, though young adults form the frequently affected subset of individuals. The common sites of this tumor include the small bones of the extremities (hands and feet), and sometimes, the skull bones
• Bizarre Parosteal Osteochondromatous Proliferation can be diagnostically-challenging, since it may resemble malignant bone tumors such as osteosarcoma or chondrosarcoma. Due to this, a tissue biopsy of the affected bone is necessary to establish a definitive diagnosis of the tumor
• Bizarre Parosteal Osteochondromatous Proliferation can be worrisome for both the healthcare seeker and healthcare provider. The tumor recurrence rate is high and generally extensive or multiple surgeries may be required to remove the tumor completely; in some cases, amputation of the affected digit or limb may be undertaken
• The prognosis of Bizarre Parosteal Osteochondromatous Proliferation with adequate surgical treatment is typically good. However, the tumor is known to reappear in nearly half the number of patients

Who gets Bizarre Parosteal Osteochondromatous Proliferation? (Age and Sex Distribution)

• Bizarre Parosteal Osteochondromatous Proliferation is an extremely rare tumor with less than 200 cases being reported worldwide
• It commonly occurs in the age group 20-40 years, although it may be seen in a wider age range (both children and adults are affected)
• Both male and females are susceptible and no preference is observed
• No ethnic or racial preference is noted

What are the Risk Factors for Bizarre Parosteal Osteochondromatous Proliferation? (Predisposing Factors)

• The risk factors for Bizarre Parosteal Osteochondromatous Proliferation are not clearly defined
• However, some researchers believe that trauma/injury to the bone may be a risk factor, since some patients present a history of bone injury at the site of involvement

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s 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 Bizarre Parosteal Osteochondromatous Proliferation? (Etiology)

• The cause of development of Bizarre Parosteal Osteochondromatous Proliferation is generally unknown
• Some scientists hypothesize that it may be triggered by injuries or bone defects. However, BPOP can also arise from healthy bones, and hence, this factor is not completely proven yet

What are the Signs and Symptoms of Bizarre Parosteal Osteochondromatous Proliferation?

The signs and symptoms of Bizarre Parosteal Osteochondromatous Proliferation may include:

• Presence of a rapidly-enlarging tumor mass on the bone surface; the bone structure is generally not compromised
• The tumor is benign, though it can be locally-aggressive
• BPOP tumors are typically solitary, well-defined, and firm to touch
• The size of the tumor may range from 1.5-4.0 cm, with an average of 2 cm
• The soft tissues and skin over the bony tumor appears as a bump; pain is generally noted
• Inflammation or redness of the skin, ulceration, or skin discoloration are not commonly noted
• Frequently, the bones of the hands and feet are involved; the carpal and tarsal bones are affected. Tumors on the hands are 4-times more common than tumors on the feet
• Other bones that may be affected include the skull bone (including the jaw), shin bone (tibia), and other long bones of the body
• The tumor mass can cause symptoms due to pressure on adjacent structures and on the nerves

How is Bizarre Parosteal Osteochondromatous Proliferation Diagnosed?

The diagnosis of Bizarre Parosteal Osteochondromatous Proliferation may include the following:

• A thorough medical history and a complete physical examination
• X-rays of the affected bone, which can establish the tumor presence
• CT or MRI scan of the affected bone to assess the extent of bone involvement
• Tissue biopsy: A tissue biopsy is performed and sent to a laboratory for a pathological examination. The pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis
• A differential diagnosis may be necessary prior to establishing a definitive diagnosis, by excluding the following tumors:
  • Chondrosarcoma
  • Florid periostitis
  • Myositis ossificans
  • Parosteal osteosarcoma
  • Turret exostosis
  • Periosteal chondroma

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 Bizarre Parosteal Osteochondromatous Proliferation?

The complications of Bizarre Parosteal Osteochondromatous Proliferation include:

• Emotional and psychological stress due to cancer concern
• Tumors on the hand or foot may present an acute difficulty in performing simple/routine tasks
• The tumor mass can cause pressure on adjacent structures, such as the nerves. In severe cases, nerve damage may occur
• Tumor recurrence following surgery is high and can vary from between 20-55%
• In some cases, more than one surgery may be necessary to address the condition
• Loss of digit or limb: Sometimes, an amputation of the involved finger, toe, or limb may be required

How is Bizarre Parosteal Osteochondromatous Proliferation Treated?

Currently, there is no well-established treatment protocol for Bizarre Parosteal Osteochondromatous Proliferation. Due to its rapid growth and potential for aggression, almost all tumors are surgically removed.

• Symptomatic treatment includes applying ice to the affected area to help reduce pain; use of painkillers
• Surgery is the treatment of choice for all lesions; sometimes, more than one invasive procedures are required. Surgery may include the following:
  • Bone tumor excision and removal; when the ‘confined’ bone tumor is removed
  • Bone removal: Surgical removal of the affected bone, or an amputation may be performed
  • Bone graft: A bone graft is a surgical procedure that involves repairing and replacing damaged bones
  • Restoration of the excised bone
• Chemotherapy and radiation therapy are not additionally recommended
• Post-operative care is important: One must maintain minimum activity levels, until the surgical wound heals
• Physical rehabilitation and occupational therapy to restore function in the affected hand or feet
• Follow-up care with regular screening and check-ups are important, since the tumor is known to recur in a majority of cases

How can Bizarre Parosteal Osteochondromatous Proliferation be Prevented?

• Presently, no clear predisposing factors have been established for this very uncommon tumor of the bone
• Besides, there is also no well-researched information on how Bizarre Parosteal Osteochondromatous Proliferation develops

Hence, the exact steps for prevention of BPOP/Nora’s Lesion have not yet been determined. Regular medical screening at periodic intervals with tests and physical examinations are strongly recommended, following diagnosis and treatment of the tumor.

What is the Prognosis of Bizarre Parosteal Osteochondromatous Proliferation? (Outcomes/Resolutions)

• The prognosis of Bizarre Parosteal Osteochondromatous Proliferation can vary from one individual to another, but is generally good with early diagnosis and treatment (surgery), in a majority
• Even though BPOP is typically a benign tumor and no malignancy is noted, it has a tendency for local invasion/aggression. Also, the tumor recurrence rate is high, since a complete tumor excision is generally difficult
• The healthcare provider must balance between performing an extensive surgical procedure to remove the entire bone (loss of digit or limb), or undertake a more conservative surgery with a risk for repeat invasive procedures in case of a recurrence (in future)

Additional and Relevant Useful Information for Bizarre Parosteal Osteochondromatous Proliferation:

• Osteochondroma is a common benign outgrowth of the bone. They account for about 30% of all benign bone tumors

The following link may help you find useful additional information on osteochondroma (bone tumor):

https://www.dovemed.com/diseases-conditions/bone-tumor-osteochondroma/