Takashi Fujisawa

Parosteal Osteosarcoma

Article
Bone, Muscle, & Joint
Diseases & Conditions
+1
Contributed byKrish Tangella MD, MBADec 17, 2018

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

  • Juxtacortical Osteogenic Sarcoma
  • Juxtacortical Osteosarcoma
  • Parosteal Osteogenic Sarcoma

What is Parosteal Osteosarcoma? (Definition/Background Information)

  • Osteosarcoma forms a class of highly-cancerous, high-mortality, bone tumor. After multiple myeloma, it is the second-most common primary tumor of the bones
  • Parosteal Osteosarcoma is a slow-growing, rare bone tumor arising from the cortical surface of the bone. Hence, these are malignant bone tumors
  • The tumor occurs over the metaphyseal region, especially the long bones, near the knees. The most common location is the posterior aspect of distal femur (thigh bone), in approximately 70% of the cases
  • Parosteal Osteosarcoma presents as a mass with signs and symptoms that include pain and decreased joint movement
  • The exact cause of the condition is unknown and presently, it is not possible to prevent Parosteal Osteosarcoma occurrence
  • A treatment of this bone tumor may involve surgery, chemotherapy, and radiation therapy. The prognosis of Parosteal Osteosarcoma depends on the stage of cancer; higher grade osteosarcomas indicate a poorer prognosis

Osteosarcomas are classified in several different ways. They may be classified based on their cause/origin, location, or even based on certain diagnostic findings.

Based on where they occur, Osteosarcoma is classified as Medullary Osteosarcoma (occurring in the bone cavity) and Surface Osteosarcoma (occurring on the bone surface).

  • Medullary Osteosarcomas are of several different types, and these include:
    • Conventional Osteosarcoma
    • Osteosarcoma of Jaw Bones
    • Post-Radiation Sarcoma
    • Osteosarcoma arising in Paget's Disease of Bone
    • Osteosarcoma in other Benign Conditions
    • Telangiectatic Osteosarcoma
    • Small Cell Osteosarcoma
    • Low-Grade Osteosarcoma
    • Multicentric Osteosarcoma
  • Surface Osteosarcomas are of several different types, and these include:
    • Parosteal Osteosarcoma
    • Periosteal Osteosarcoma
    • High-Grade Surface Osteosarcoma

Who gets Parosteal Osteosarcoma? (Age and Sex Distribution)

  • Parosteal Osteosarcoma may occur during adolescence, young adult, or mid-to-late adult stage, typically between the ages 12-60 years
  • Both men and women are prone to the condition
  • However, it is thought that more commonly young women are affected by Parosteal Osteosarcoma, frequently in the 3rd decade of life

What are the Risk Factors for Parosteal Osteosarcoma? (Predisposing Factors)

The risk of Parosteal Osteosarcoma is linked to the following factors:

  • A preexisting bone lesion suggestive of Paget’s disease of bone
  • A previously performed radiotherapy for other cancer conditions - the tumor may be radiation-induced. The radiation has an expected side effect of damaging the genetic material in the normal cells. This can lead to the development of a “secondary” cancer

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 Parosteal Osteosarcoma? (Etiology)

The exact cause and mechanism of Parosteal Osteosarcoma formation, is unknown.

  • The tumor can occur due to some preexisting conditions and abnormalities (termed as a secondary osteosarcoma)
  • Such preexisting conditions could include radiation-exposure, genetic anomalies, and the presence of multiple chondroma
  • The following genetic conditions have been observed:
    • Cytogenetic change with giant marker chromosomes carrying amplified DNA materials from 12q13-15 region
    • Amplification of CDK4 and MDM2 genes, which are important in cell cycle regulation
  • A radiation-influenced tumor takes many years to develop, after the radiation exposure has ceased. This radiation may have been previously administered for treating other cancers

What are the Signs and Symptoms of Parosteal Osteosarcoma?

The presentations are based on the location of the tumor. Parosteal Osteosarcoma signs and symptoms may include:

  • A painless mass that lasts for years
  • Symptoms can be present from few months to years
  • Decreased range of joint movements in the affected limb, in some cases
  • Dull pain and local tenderness
  • Frequently, the long bones of the leg (thigh bone near the knee in most cases, and the shinbone) and the upper arm bone (humerus) is affected

How is Parosteal Osteosarcoma Diagnosed?

A diagnosis of Parosteal Osteosarcoma is made using the following tools:

  • Physical examination, evaluation of patient’s medical history
  • Plain x-ray of the affected region:
    • The tumor shows up as a lobulated, mushroom-like mass protruding from underlying cortex with broad based attachment
    • It has an irregular pattern of mineralization
    • Parosteal Osteosarcoma shows cartilaginous cap that can be confused with osteosarcoma
  • CT or MRI scan of the affected region
  • Microscopic and pathological evaluation of tissue biopsy - the specimen is examined under a microscope by a pathologist, to arrive at a definitive diagnosis
  • Molecular testing of biopsy, using CDK4 and MDM2 markers can be helpful

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 Parosteal Osteosarcoma?

The possible complications of Parosteal Osteosarcoma include:

  • The well-differentiated Parosteal Osteosarcoma can become dedifferentiated Parosteal Osteosarcoma. The presence of tumor dedifferentiation is associated with local recurrence and distant metastases
  • They are known to recur, even on surgical excision and removal
  • Deep-seated tumors (those buried inside the body tissues) may cause damage to adjoining tissues and organs
  • Blood loss during invasive treatment methods may be heavy
  • Damage to vital nerves, blood vessels, and surrounding structures, during surgery
  • Side effects from chemotherapy (such as toxicity), radiation therapy

How is Parosteal Osteosarcoma Treated?

Treatment measures for Parosteal Osteosarcoma include the following:

  • Surgery is the treatment of choice. A wide excision with more than 1 cm surgical margin is considered adequate
  • Recurrent cases may require amputation of the affected limb portion
  • Chemotherapy may be required in areas of dedifferentiation
  • Radiation therapy may be given depending upon the stage of the tumor
  • Post-operative care is important: A minimum activity level is to be ensured, until the surgical wound heals
  • Follow-up care with regular screening and check-ups are important

How can Parosteal Osteosarcoma be Prevented?

  • Parosteal Osteosarcoma is thought to occur due to a variety of reasons, such as cytogenetic change with giant marker chromosomes carrying amplified DNA materials from 12q13-15 region; it cannot be prevented
  • However, the presence of any tumor or lesion should be immediately informed to the physician and periodic follow-up and screening maintained
  • Regular medical screening at periodic intervals with blood tests, scans, and physical examinations, are mandatory for those who have already endured the tumor. This is due to both its high metastasizing potential and chances of recurrence. Often several years of active vigilance is necessary

What is the Prognosis of Parosteal Osteosarcoma? (Outcomes/Resolutions)

The prognosis of Parosteal Osteosarcoma, depends upon the stage of the tumor

  • Lower the stage, better is the prognosis
  • Higher the stage, poorer is the prognosis

Largely, Parosteal Osteosarcoma prognosis is much more favorable, when compared to that of conventional high-grade osteosarcoma. Certain poor prognostic factors include:

  • Incomplete excision
  • Presence of tumor dedifferentiation, associated with local recurrence and distant metastases

Additional and Relevant Useful Information for Parosteal Osteosarcoma:

There are approximately 1000 cases of osteosarcomas, diagnosed each year in the United States.

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Krish Tangella MD, MBA

Pathology, Medical Editorial Board, DoveMed Team

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