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Inflammatory Myofibroblastic Tumor of Thyroid Gland

Last updated Oct. 12, 2018

Approved by: Maulik P. Purohit MD, MPH

Inflammatory Myofibroblastic Tumor of Thyroid Gland is a very rare, mostly benign tumor of the thyroid gland (located in the neck). They generally occur in older populations.


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

  • Inflammatory Pseudotumor of Thyroid Gland
  • Plasma Cell Granuloma of Thyroid Gland
  • Thyroidal Inflammatory Fibrosarcoma

What is Inflammatory Myofibroblastic Tumor of Thyroid Gland? (Definition/Background Information)

  • Inflammatory Myofibroblastic Tumor of Thyroid Gland is a very rare, mostly benign tumor of the thyroid gland (located in the neck). They generally occur in older populations
  • Inflammatory myofibroblastic tumor (IMT) is generally considered as a benign tumor with aggressive behavior (low-grade tumor), which can occur anywhere in the body
  • The cause of Thyroidal Inflammatory Myofibroblastic Tumor is generally unknown, though an association with genetic mutations is observed. There are also no well-established risk factors for this tumor type
  • The signs and symptoms of Inflammatory Myofibroblastic Tumor of Thyroid Gland may include a painless mass in the neck, fever, and even hypothyroidism. Complications, such as tumor recurrence after treatment, is generally not known to occur
  • The mainstay of treatment of Inflammatory Myofibroblastic Tumor of Thyroid Gland is a surgical excision that can be curative. The prognosis is generally good on tumor removal, but some tumors are known to be aggressive and/or metastasize (rare cases)

Who gets Inflammatory Myofibroblastic Tumor of Thyroid Gland? (Age and Sex Distribution)

  • Inflammatory Myofibroblastic Tumor of Thyroid Gland is typically seen in middle-aged and older adults (older than 50 years); Thyroidal IMT in children is unusual
  • Very few cases (less than 20) of IMT of Thyroid Gland have been recorded in the medical literature
  • Both males and females are affected, though a strong predilection for females is noted
  • All races and ethnic groups are at risk for the condition

Note: Most inflammatory myofibroblastic tumors are found in the lung, which is the most common site of the tumor. In such cases, these tumors are frequently diagnosed in middle-aged adults. However, in contrast, the average age of presentation for extrapulmonary IMT (IMT outside the lung) is around 10 years.

What are the Risk Factors for Inflammatory Myofibroblastic Tumor of Thyroid Gland? (Predisposing Factors)

  • Presently, the specific risk factors for Thyroidal Inflammatory Myofibroblastic Tumor are unknown or unidentified
  • In some cases, an association with Hashimoto's thyroiditis is observed

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 Inflammatory Myofibroblastic Tumor of Thyroid Gland? (Etiology)

The cause of development of Inflammatory Myofibroblastic Tumor of Thyroid Gland is generally unknown.

  • Some research scientists believe that the cause of the condition is mostly due to genetic mutations, which results in tumor formation. In over 40% of the tumors, ALK gene mutation has been observed
  • Some believe that the inflammatory myofibroblastic tumor is the result of an inflammatory reactive process and not a true tumor
  • It is also believed by some researchers that the tumor may arise due to viral infections caused by human herpes virus 8 (HHV8) or Epstein-Barr virus (EBV)

What are the Sign and Symptoms of Inflammatory Myofibroblastic Tumor of Thyroid Gland?

The signs and symptoms depend on the size of the tumor. Specific signs and symptoms of Inflammatory Myofibroblastic Tumor of Thyroid Gland may include:

  • Small tumors usually do not cause any symptoms. But, occasionally they may become painful, if surrounding structure is compressed
  • Lump in the neck or a sensation of a lump in the throat
  • Absence of pain
  • Fever and fatigue
  • Large tumors may cause difficulty in speaking, eating, swallowing, and/or breathing
  • Persistent cough

The inflammatory myofibroblastic tumor may range in size from 0.5 to 9 cm (average size 3-4 cm).

If the tumor affects the functioning of the thyroid gland, then the signs and symptoms of hypothyroidism may be seen, which include:

  • Enlarged thyroid gland initially; shrunken thyroid gland (later in the disease stage)
  • Difficulty concentrating or thinking
  • Fatigue and tiredness
  • Dry skin and hair loss (may be excess during showering)
  • Heavy and irregular periods (in women)

In some cases, when the tumor is associated with Hashimoto's thyroiditis, signs and symptoms of hypothyroidism (as above) may be present.

How is Inflammatory Myofibroblastic Tumor of Thyroid Gland Diagnosed?

A diagnosis of Inflammatory Myofibroblastic Tumor of Thyroid Gland may be undertaken using the following tests and exams:

  • Complete evaluation of family (medical) history, along with a thorough physical examination
  • Individuals with the tumor may be referred to an ear, nose, and throat (ENT) physician (otolaryngologist) for further examination
  • Thyroid function studies
  • Plain X-ray of the neck
  • Ultrasound scan of the thyroid gland
  • A thyroid scan can be performed to create an image of the thyroid gland using radioactive iodine
  • CT or CAT scan with contrast of the head and neck usually shows a well-defined mass. This radiological procedure creates detailed 3-dimensional images of structures inside the body
  • MRI scans of the head and neck: Magnetic resonance imaging (MRI) uses a magnetic field to create high-quality pictures of certain parts of the body, such as tissues, muscles, nerves, and bones. These high-quality pictures may reveal the presence of the tumor

Although the above modalities can be used to make an initial diagnosis, a tissue biopsy of the tumor is necessary to make a definitive diagnosis to begin treatment. The tissue for diagnosis can be procured in multiple different ways which include: 

  • Fine needle aspiration (FNA) biopsy of the tumor: A FNA biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a FNA biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy is preferred
  • Thyroid core biopsy of the tumor
  • Thyroid open biopsy of the tumor

Tissue biopsy of the tumor:

  • A tissue biopsy of the tumor is performed and sent to a laboratory for a pathological examination. A 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. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis
  • Biopsy specimens are studied initially using Hematoxylin and Eosin staining. The pathologist then decides on additional studies depending on the clinical situation
  • Sometimes, the pathologist may perform special studies, which may include immunohistochemical stains, molecular testing, and very rarely, electron microscopic studies to assist in the diagnosis

Note: Inflammatory Myofibroblastic Tumors are very rare. Due to this, it typically causes diagnostic challenges to the pathologist while trying to establish an accurate diagnosis.

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 Inflammatory Myofibroblastic Tumor of Thyroid Gland?

Some potential complications of Inflammatory Myofibroblastic Tumor of Thyroid Gland include:

  • They can mimic cancer and cause considerable emotional stress in the affected individual
  • In rare cases, these tumors can be locally aggressive
  • Also, very rarely, these tumors are known to metastasize; in which case the tumor is known as Malignant Inflammatory Myofibroblastic Tumor

Recurrence of the tumor after treatment is not generally reported with IMT of Thyroid.

How is Inflammatory Myofibroblastic Tumor of Thyroid Gland Treated?

Inflammatory Myofibroblastic Tumor of Thyroid Gland may be treated through the following measures:

  • Surgical removal of the entire tumor is the preferred method of treatment. A surgical procedure, called partial or total thyroidectomy, may be performed to completely remove the tumor
  • In young children, if the tumors cannot be surgically removed, then corticosteroid administration is found to be beneficial
  • Chemotherapy may help, if the condition recurs , if there is a local invasion, or a distant metastasis is noted (in very rare cases)
  • Occasionally, some tumors are known to disappear over time, without any treatment

Observation and periodic checkups to monitor the condition is recommended following treatment.

How can Inflammatory Myofibroblastic Tumor of Thyroid Gland be Prevented?

Presently, there are no specific methods or guidelines to prevent Inflammatory Myofibroblastic Tumor of Thyroid Gland.

What is the Prognosis of Inflammatory Myofibroblastic Tumor of Thyroid Gland?

  • An early diagnosis and prompt treatment of Inflammatory Myofibroblastic Tumor of Thyroid Gland generally yields better outcomes than a late diagnosis and delayed treatment
  • The prognosis on timely surgical removal of the tumor is generally good. On a complete excision and removal, Thyroidal IMT is generally not known to recur
  • Some tumors are known to spontaneously regress and disappear. But, some tumors are known to metastasize (occasionally)

Additional and Relevant Useful Information for Inflammatory Myofibroblastic Tumor of Thyroid Gland:

The following article link will help you understand other cancers and benign tumors:

http://www.dovemed.com/diseases-conditions/cancer/

What are some Useful Resources for Additional Information?


References and Information Sources used for the Article:


Helpful Peer-Reviewed Medical Articles:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: May 28, 2016
Last updated: Oct. 12, 2018