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COMMENT ON TABLE I.1.– Genes: names of the genes directly linked to the predisposition mentioned and which were reported in a diagnostic report, in France, in 2016. IC+: Index cases identified in 2016 as carriers of a genetic alteration in the genes mentioned; REL+: relatives identified in 2016 as carriers of a genetic alteration in the genes mentioned; AR: allelic status for genes with autosomal recessive transmission; BI: index or relatives carrying biallelic mutations; MONO: index or relatives carrying a monoallelic mutation; *constitutional hypermethylation of the promoter of the MLH1 gene; **CEBPA, ETV6, GATA2, KIT, MPL, SBDS, SH2B3, SRP72, WAS, etc.; ***BRAF, CBL, HRAS, KRAS, MAP2K1, MAP2K2, NRAS, PTPN11, RAF1, RIT1, SHOC2, SOS1, SOS2, etc.
DEFINITION.– DNA methylation is the enzymatically controlled addition of a methyl group to a nucleotide base (such as cytosine in eukaryotes) in a DNA molecule that plays a role in the regulation of gene expression (e.g., by inhibiting gene transcription).
Table I.2 Order of syndromes according to their frequency (as deduced from statistics on index patients and their relatives carrying a genetic alteration predisposing to cancer, identified in the various accredited centers in France in 2016). *IC+ and REL+: index patient and relatives
| Genetic predisposition to cancer | *IC+ and REL+ | % | Rank |
| Breast ovarian syndrome (including isolated ovarian cancers) | 4,356 | 52.62 | 1 |
| Lynch syndrome | 1,148 | 13.87 | 2 |
| Neurofibromatosis | 682 | 8.24 | 3 |
| Familial adenomatous polyposis | 528 | 6.38 | 4 |
| Endocrine neoplasia | 213 | 2.57 | 5 |
| Hereditary paraganglioma–pheochromocytoma | 184 | 2.22 | 6 |
| Birt–Hogg–Dubé syndrome | 167 | 2.02 | 7 |
| RASopathies and Noonan syndrome | 159 | 1.92 | 8 |
| Familial malignant melanoma | 120 | 1.45 | 9 |
| Gorlin syndrome | 120 | 1.45 | 10 |
| Li–Fraumeni syndrome | 71 | 0.86 | 11 |
| Ataxia–telangiectasia | 59 | 0.71 | 12 |
| Hyperparathyroidism | 51 | 0.62 | 13 |
| Cowden syndrome | 51 | 0.62 | 14 |
| Fanconi syndrome | 50 | 0.60 |