Muir-Torre Syndrome (MTS)

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What is Muir-Torre Syndrome?

Muir-Torre syndrome (MTS) is a rare autosomal dominant genetic disease characterized by tumors of the sebaceous (oil) glands of the skin such as sebaceous adenoma, as well as malignancies of internal organs, such as colorectal, breast, endometrial, ovarian, genitourinary, and small bowel cancers. Of these, colorectal cancer is the most common, which accounts for about 50% of all primary cancers in MTS. Approximately 15% of female MTS patients develop endometrial cancer. Muir-Torre syndrome is considered to be a subtype of Lynch syndrome, which is also known as hereditary nonpolyposis colorectal cancer (HNPCC).

Origin of the Term "Muir-Torre Syndrome"

The syndrome is named after Drs. E.G. Muir and D. Torre who independently described several aspects of the syndrome. Muir and his colleagues in 1967 first described a patient with multiple cancers of the colon, duodenum, and larynx (voice box) in association with keratoacanthoma (cancer of sunburnt areas of the skin). Torre in 1968 described the occurrence of multiple sebaceous tumors (tumors of the oil glands) of the skin.

Epidemiology of Muir-Torre Syndrome

Muir-Torre syndrome is a very rare condition, which has been reported to occur in Caucasians in western countries. Data from developing countries is lacking. It is more prevalent in men with a male-to-female ratio of 3:2. The median age of onset of symptoms is usually 53 years, but can appear as early as 23 years or as late as 89 years. Muir-Torre syndrome occurs in 9.2% of patients suffering from Lynch syndrome.

What are the Causes of Muir-Torre Syndrome?

Muir-Torre syndrome is caused by genetic mutations (alterations) in the deoxyribonucleic acid (DNA) mismatch repair (MMR) genes, which help to repair damaged parts of DNA. The DNA MMR genes include mutS homolog 2 (MSH2), mutS homolog 6 (MSH6) and mutL homolog 1 (MLH1). These genes maintain genomic integrity by correcting errors in base pairing during DNA replication. Sometimes, there may be loss of DNA MMR function due to inactivating mutations of MMR genes leading to the accumulation of mutations across the genome and mainly in the microsatellites (short repetitive DNA sequences), leading to microsatellite instability.

What Causes Muir-Torre Syndrome?

What are the Symptoms and Signs of Muir-Torre Syndrome?

Muir-Torre syndrome exhibits some general symptoms and signs. Others include symptoms associated with the skin (cutaneous symptoms) and internal organs (visceral symptoms). These are briefly highlighted below:

General Symptoms

The general symptoms include the following:
  • Bleeding along with stool
  • Painful abdominal mass
  • Weight loss
  • Loss of appetite
  • Blood in vomit (hematemesis)
  • Weakness and fatigue
  • Anemia
  • Menstrual abnormalities
Cutaneous Symptoms

These are associated with the sebaceous glands. Sebaceous neoplasms have the potential to arise from any sebaceous gland in the body, but are most commonly seen on the nose, eyelids, and other areas where there is a high density of sebaceous glands. The sebaceous neoplasms include the following:
  • Sebaceous Adenoma: A slow-growing, benign tumor of the sebaceous glands, which is the most characteristic feature of MTS patients.
  • Sebaceous Epithelioma: A yellowish, benign, nodular tumor of the epithelium of sebaceous glands.
  • Sebaceous Carcinoma: This is an invasive cancer of the sebaceous glands that occurs most commonly on the eyelids.
  • Keratoacanthoma: A skin tumor that occurs on sun-exposed areas as firm nodules, which are usually tan-colored or reddish in color.
Visceral Symptoms
  • Colorectal Cancer: This is a cancer of the large intestine and rectum.
  • Endometrial Cancer: This is a cancer of the mucus membrane lining the uterus.
  • Urological Cancer: These are cancers of any part of urinary system, including the kidneys, ureters, urinary bladder, or urethra.
  • Breast Cancer: This is a cancer of the breasts which appears as a lump in the breast tissue.
  • Other Cancers: Besides the above, cancers may arise in other organs too. These include cancers of the stomach, ovaries, small bowel, and prostate. Cancers of the lymphatic system (lymphoma) and blood (leukemia) may also occur.

How do you Diagnose Muir-Torre Syndrome?

The following diagnostic approaches can be adopted:

Screening: It is important that MTS is diagnosed as early as possible. Therefore, screening for tumors and/or invasive cancer should always be performed regularly. The following screening methods may be adopted:
  • Physical Examination: These should be done annually, which include:
    • Pelvic exam, breast exam and PAP smear in female patients.
    • Prostate and testicular exam in male patients.
  • CT Scan: Computed tomography (CT) scan may be used to visualize the abdomen and pelvis.
  • Colonoscopy: This should be done annually from the age of 40 years.
  • Laboratory Investigations: These include the following blood tests and urine tests:
    • Complete blood count (CBC)
    • Cancer antigen 125 (CA-125)
    • Carcinoembryonic antigen (CEA)
    • Fecal occult blood test (FOBT)
    • Urinalysis
Biopsy: Tissue biopsy samples can be taken from sites where cancer is suspected to be present. The tissue samples are stained with dyes and then observed by microscopy.

Immunohistochemistry: This is an immunological technique that uses antibodies that bind to specific antigens present on the tissue samples. This technique is very useful for evaluating MSH-2 and MLH-1 expression levels. This is a simple and rapid technique used for identifying the mutated genes and obtaining an early diagnosis of MTS presenting with skin lesions.

Genetic Tests: These tests are used to identify any changes that destabilize the chromosomes thereby hindering their functioning. This is technically termed as microsatellite instability analysis.

How do you Treat Muir-Torre Syndrome?

Muir-Torre syndrome can be treated by the following approaches:
  • Medical Treatment: Muir-Torre syndrome can be successfully treated by using the drugs isotretinoin and interferon α-2a. Cancers that occur as a result of MTS can be treated by chemotherapy or radiotherapy.
Drugs to Treat Muir-Torre Syndrome
  • Surgical Treatment: There is a high frequency of metastasis and death (sometimes up to 25%) in MTS. This requires general surgical excision to remove the tumors. A special type of surgical procedure called Mohs micrographic surgery is used to treat skin cancer. In this procedure, each layer of the cancerous tissue is excised and sequentially examined under the microscope until the whole cancer tissue has been removed.

What are the Risk Factors and Estimated Cancer Risks Associated with Muir-Torre Syndrome?

The following risk factors can predispose an individual to MTS:
  • Family history of MTS, colorectal cancer and sebaceous tumors.
  • Mutations in the MLH1 and MSH2 genes.
  • Individuals having a defective DNA mismatch repair mechanism.
The estimated cancer risk (%) for various types of cancer associated with MTS are tabulated below:

Type of CancerEstimated Cancer Risk (%)
Sebaceous gland cancerHigh risk
Colorectal cancer80%
Endometrial cancer20-60%
Stomach cancer11-19%
Ovarian cancer9-12%
Hepatobiliary cancer2-7%
Urinary tract cancer4-5%
Small bowel cancer1-4%
Brain cancer1-3%

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