Ovarian neoplasm and endometrioid carcinoma in a patient with Turcot syndrome

Phenotypic and genotypic characterisation of biallelic mismatch repair deficiency (BMMR-D) syndrome

Lynch syndrome, the most common inherited colorectal cancer syndrome in adults, is an autosomal dominant condition caused by heterozygous germ-line mutations in DNA mismatch repair (MMR) genes MLH1, MSH2, MSH6 and PMS2. Inheriting biallelic (homozygous) mutations in any of the MMR genes results in a different clinical syndrome termed biallelic mismatch repair deficiency (BMMR-D) that is characterised by gastrointestinal tumours, skin lesions, brain tumours and haematologic malignancies. This recently described and under-recognised syndrome can present with adenomatous polyps leading to early-onset small bowel and colorectal adenocarcinoma. An important clue in the family history that suggests underling BMMR-D is consanguinity. Interestingly, pedigrees of BMMR-D patients typically show a paucity of Lynch syndrome cancers and most parents are unaffected. Therefore, a family history of cancers is often non-contributory. Detection of BMMR-D can lead to more appropriate genetic counselling and the implementation of targeted surveillance protocols to achieve earlier tumour detection that will allow surgical resection. This review describes an approach for diagnosis and management of these patients and their families.

Paediatric intestinal cancer and polyposis due to bi-allelic PMS2 mutations: case series, review and follow-up guidelines

BACKGROUND

Bi-allelic germline mutations of one of the DNA mismatch repair genes, so far predominantly found in PMS2, cause constitutional MMR-deficiency syndrome. This rare disorder is characterised by paediatric intestinal cancer and other malignancies. We report the clinical, immunohistochemical and genetic characterisation of four families with bi-allelic germline PMS2 mutations. We present an overview of the published gastrointestinal manifestations of CMMR-D syndrome and propose recommendations for gastro-intestinal screening.

METHODS AND RESULTS

The first proband developed a cerebral angiosarcoma at age 2 and two colorectal adenomas at age 7. Genetic testing identified a complete PMS2 gene deletion and a frameshift c.736_741delinsTGTGTGTGAAG (p.Pro246CysfsX3) mutation. In the second family, both the proband and her brother had multiple intestinal adenomas, initially wrongly diagnosed as familial adenomatous polyposis. A splice site c.2174+1G>A, and a missense c.137G>T (p.Ser46Ile) mutation in PMS2 were identified. The third patient was diagnosed with multiple colorectal adenomas at age 11; he developed a high-grade dysplastic colorectal adenocarcinoma at age 21. Two intragenic PMS2 deletions were found. The fourth proband developed a cerebral anaplastic ganglioma at age 9 and a high-grade colerectal dysplastic adenoma at age 10 and carries a homozygous c.2174+1G>A mutation. Tumours of all patients showed microsatellite instability and/or loss of PMS2 expression.

CONCLUSIONS

Our findings show the association between bi-allelic germline PMS2 mutations and severe childhood-onset gastrointestinal manifestations, and support the notion that patients with early-onset gastrointestinal adenomas and cancer should be investigated for CMMR-D syndrome. We recommend yearly follow-up with colonoscopy from age 6 and simultaneous video-capsule small bowel enteroscopy from age 8.

Café-au-lait spots and early onset colorectal neoplasia: a variant of HNPCC?

BACKGROUND

Café-au-lait spots (CALS) are classically found in neurocutaneous syndromes such as neurofibromatosis, but have not been associated with hereditary colorectal cancer. However, review of hereditary colorectal cancer case reports reveals occasional description of CALS on physical exam.

METHODS

We describe the colonic and extracolonic phenotype in a family with CALS and early onset colorectal neoplasia (adenomas and/or cancer) and review 23 additional families reported in the literature.

RESULTS

Among the 24 families, 32/59 (54.2%) individuals had colorectal adenomas diagnosed at a mean age of 15.7 +/- 1.1 (SE) years (range 5-38 years). The majority (24/32, 75.0%) of persons at first colorectal examination had oligopolyposis (< 100 polyps) versus polyposis (> or = 100 polyps). Forty-two of 59 (71.2%) individuals were affected with colorectal cancer, diagnosed at a mean age of 31.9 +/- 2.7 years (range 5-70 years). A brain tumor was found in 28/59 (47.5%) affected individuals (4 families with 2 or more cases) with an overall mean age of diagnosis of 16.5 +/- 1.2. Lymphoma and/or leukemia was found in 8/24 (33.3%) families (one family with 3 cases). Two families had mutation of the mismatch repair gene, hPMS2 (1 with homozygous germline mutation), while two carried homozygous germline mutations of another mismatch repair gene, hMLH1.

CONCLUSIONS

Café-au-lait spots with early onset colorectal neoplasia may identify families with a variant of HNPCC characterized by oligopolyposis, glioblastoma at young age, and lymphoma. This variant may be caused by homozygous mutation of the mismatch repair genes, such as hPMS2 or hMLH1.