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

• PM (Proliferative Myositis)

What is Proliferative Myositis? (Definition/Background Information)

• Proliferative Myositis (PM) is a rapidly-growing benign lesion that occurs in the skeletal muscles (intramuscular) and forms a mass. It is described as a variant of nodular fasciitis
• The tumor forms a mass of a type of cells, known as fibroblastic/myofibroblastic cells, which are observed to be abnormally-sized
• Proliferative Myositis frequent sites are the chest and back. It can cause pain and tenderness at the site of the tumor
• A complete surgical removal of Proliferative Myositis results in a cure and is the treatment of choice; a recurrence of the tumor is not very common
• The prognosis of Proliferative Myositis is excellent on suitable surgical treatment, since it is a benign tumor

Who gets Proliferative Myositis? (Age and Sex Distribution)

• Proliferative Myositis is commonly seen in middle-age and older adults (40-70 years); however, young adults and, in a few cases, children have also been affected
• Individuals of both genders (males and females) are affected
• The tumor is seen in individuals of all races and ethnic groups

What are the Risk Factors for Proliferative Myositis? (Predisposing Factors)

• The risk factors for Proliferative Myositis are unknown in many cases
• In some cases, a history of trauma at the site of the tumor is observed. Some reports indicate that over 30% of the individuals with Proliferative Myositis may have experienced some form of trauma

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 Proliferative Myositis? (Etiology)

Proliferative Myositis is a benign tumor of unknown cause.

• Very rarely, some chromosomal abnormalities have been detected
• However, some researchers indicate that this may be an aberration caused most probably due to advancing age of the individual

What are the Signs and Symptoms of Proliferative Myositis?

The signs and symptoms of Proliferative Myositis include:

• A rapidly-growing solitary mass in the skeletal muscles; the tumor may double in size within a few weeks
• Proliferative Myositis averages 3-4 cm in size; it is typically not larger than 6 cm
• It is mostly observed in the torso (chest and back), followed by the shoulders and forearm. In some cases, the thigh may be involved
• The tumor margin/borders are not well defined
• Pain in the affected region with feeling of tenderness is noted; the pain may be significant. In some cases, there may be no pain

How is it Diagnosed of Proliferative Myositis?

Proliferative Myositis diagnosis may involve the following tests and exams:

• Physical examination and evaluation of medical history
• Radiological studies of the affected region such as MRI and CT scans; these are generally found to be effective in studying/diagnosing the tumor
• Tissue biopsy: A tissue biopsy is performed and sent to a laboratory for a pathological examination, who 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

Note: Proliferative Myositis can grow into the muscle fibers and exhibit what is known as a “checkerboard pattern” that can be seen on tumor examination under a microscope.

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 Proliferative Myositis?

The possible complications from Proliferative Myositis include:

• The rapid growth of the tumor may give rise to emotional stress due to concern for cancer
• Rarely, the tumor can recur following its surgical removal

How is Proliferative Myositis Treated?

• The treatment of Proliferative Myositis is a complete surgical excision, which can result in a cure
• The tumor is surgically removed, since it can cause concern in the healthcare seeker and the healthcare provider, due to its rapid growth
• Occasionally, these tumors are known to spontaneously resolve by themselves

How can Proliferative Myositis be Prevented?

Currently, Proliferative Myositis is a condition that is generally not preventable.

What is the Prognosis of Proliferative Myositis? (Outcomes/Resolutions)

• The prognosis of Proliferative Myositis is generally excellent after a local excisional surgery to remove the benign mass
• Recurrence risk following tumor removal is very minimal and no metastasis is observed (even though PM may exhibit rapid growth)

Additional and Relevant Useful Information for Proliferative Myositis:

• Proliferative Myositis is not as frequently seen as nodular fasciitis
• Nodular fasciitis is a benign, rapidly growing mass that frequently affects the upper extremities (hands). This benign tumor reduces in size, after a certain time period of rapid growth (usually by 6 weeks)

The following link can help you understand nodular fasciitis:

https://www.dovemed.com/diseases-conditions/nodular-fasciitis/