|Classification and external resources|
Muir–Torre syndrome (MTS) is a rare hereditary, autosomal dominant cancer syndrome:663 that is thought to be a subtype of HNPCC. Individuals are prone to develop cancers of the colon, breast, and genitourinary tract, and skin lesions, such as keratoacanthomas and sebaceous tumors. The genes affected are MLH1, MSH2, and more recently, MSH6, and are involved in DNA mismatch repair.
Muir-Torre Syndrome is characterized by both:
- At least a single sebaceous gland tumor (either an adenoma, an epithelioma, or a carcinoma)
- A minimum of one internal malignancy
The Amsterdam criteria are frequently used to diagnose Lynch syndrome and Muir–Torre syndrome. They include the following:
- 3 or more relatives with an HNPCC-associated cancer (i.e., colorectal, cancer of the endometrium, small bowel, ureter, or renal pelvis)
- 2 or more successive generations affected by cancer
- 1 or more persons with cancer is a first-degree relative of the other 2, at least 1 case of colorectal cancer younger than age 50 years, a diagnosis of familial adenomatous polyposis has been excluded, tumors are verified by histologic examination
Muir-Torre Syndrome is a genetic condition. Mutations in MLH1 and MSH2 are linked with the disease. These genes code for DNA mismatch repair genes, and mutations increase the risk of developing cancerous qualities.
The 2 major MMR proteins involved are hMLH1 and hMSH2. Approximately 70% of tumors associated with the MTS have microsatellite instability. While germline disruption of hMLH1 and hMSH2 is evenly distributed in HNPCC, disruption of hMSH2 is seen in greater than 90% of MTS patients.
Gastrointestinal and genitourinary cancers are the most common internal malignancies. Colorectal cancer is the most common visceral neoplasm in Muir–Torre syndrome patients.
Immunohistochemistry is now being used more often to diagnose patients likely to have Muir-Torre. Sebaceous neoplasms are only infrequently encountered, and immunohistochemistry is reliable and readily available, so researchers have recommended its use. Routine immunohistochemical detection of DNA mismatch repair proteins help identify hereditary DNA mismatch repair deficiency.
Genetic Overlap with Turcot Syndrome
A couple studies have been conducted on patients with both Muir-Torre Syndrome and Turcot Syndrome. It is thought that the two may have some genetic overlap. Both have been associated defects in MLH1 and MSH2 genes.
In one study, a patient with defective MSH2 and MSH6 mismatch repair genes exhibited both syndromes. This is the first case where a patient with genotypic changes consistent with HNPCC has been properly diagnosed with an overlap of both syndromes. Along with neoplasms of the sebaceous gland, this patient developed cerebral neoplasms, characteristic of Turcot Syndrome.
- List of cutaneous conditions
- List of cutaneous conditions associated with increased risk of nonmelanoma skin cancer
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