|ECR 2019 / C-2457|
|Recognizing Cowden Syndrome; radiological findings to look for|
Cowden Syndrome is an autosomal dominant disorder. It belongs to a group linked to germline mutations in the Phosphate and Tensin homolog tumour suppressor gene (PTEN) that includes basically three disorders: the Cowden Syndrome, the Bannayan-Ruvalcaba Syndrome and the Proteus-like Syndrome. Given the common genetic aetiology of the aforementioned syndromes, they are grouped under the term PTEN hamartoma tumour syndromes (PTHS).
Amongst these three syndromes, Cowden Syndrome, is the prototype, the most well-known and better characterised one. It was described for the first time in 1962 by Doctors Macey Dennis and Kenneth M. Lloyd, and diagnostic criteria were depicted for the first time by the International Consortium of Cowden in 1995. Criteria continue to evolve and change at the same time that new research and investigations define Cowden Syndromes´ clinical spectre.
Previous studies estimate an incidence of 1 case per 200,000 people, although this number is thought to be underestimated. This inherited syndrome has no gender predilection, but some manifestations are more likely to appear in males; thyroid cancer, while others will appear more frequently in females; breast cancer.
It is a multisystem disease with increased risk for malignancies (breast, thyroid, kidney, and endometrium), as well as benign hamartomatous overgrowth of several tissues (skin, mucosae, colon, thyroid…).
Among the benign lesions we can find various mucocutaneous changes that are considered to be pathognomonic of Cowden Syndrome, including trichilemmomas and other facial papules, acral keratosis and oral papilloma. Other benign findings include lipomas, colonic polyps and thyroiditis.
Patients have traditionally been considered at a higher risk for developing breast and thyroid tumours, both benign and malignant.
Other associated features, such as Lhermitte-Duclos disease, are less frequent diseases, but it is important for both clinicians and radiologists to be acquaintance with them, since they could be signals that lead to Cowden Syndrome diagnosis.
The spectrum of mutations of the germline detected in these syndromes expands along the PTEN gene codification sequence; gene that is found in 10q 23.3 chromosome.
PTEN gene is a tumour suppressor gene involved in many different cell signalling pathways, such as the PI2K/AKT/mTOR pathways. Mutations in PTEN tumour suppressor gene therefore causes, a dysregulation of the AKT pathways, which subsequently leads to a decrease in the apoptosis and an increase of cellular growth.
In the last decade, it has become obvious that some individuals with Cowden Syndrome do not present with PTEN germline mutations, but rather show mutations in other susceptible genes in the PTEN germline, or in other germlines. Moreover, unfortunately, the attempts to establish a clear correlation between the clinical phenotypic variations and the genotype have been unsuccessful, and due to high risk of cancer development, patients with PTHS must be offered a special management, independent of the type of mutation.
For this reason, molecular genetic testing can be offered to these patients to assess this mutation, nevertheless, the consensus diagnostic criteria should always be used. These criteria are listed in Table 1. (Fig. 1)
Diagnosis will be established when encountering:
• ≥ 3 major criteria: including macrocephaly, Lhermitte-Duclos and gastrointestinal hamartomas
• 2 major y 3 minor criteria
Family diagnosis (one family member already diagnosed):
• Any major criteria with or without minor criterion
• One major and one minor criterion
• 3 minor criteria
Criteria highlighted in bold are nowadays considered pathognomonic of Cowden Syndrome.
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