Serrated polyposis syndrome: Molecular, pathological and clinical aspects

Table 3 Characteristics of serrated polyps

Polyp name	Alternative terminology	Morphology and significance	Predominant location	Molecular features
Hyperplastic polyp, goblet type	Type 1 hyperplastic polyp	Subtype of hyperplastic polyp with conspicuous goblet cells and showing the least morphologic deviation from normal; Described as goblet-cell rich type	Distal colon: Sigmoid and rectum	Frequent KRAS mutation (54%)
Hyperplastic polyp, microvesicular type	Type 2 hyperplastic polyp	Variant of hyperplastic polyp in which columnar cells have mucin-filled vesicles within the apical cytoplasm and goblet cells are relatively inconspicuous	Right colon and distal colon	Frequent BRAF mutation (76%) and CIMP (68%)
Sesile serrated adenoma	Sessile serrated polyp; Serrated polyp with atypical proliferation	Advanced type of serrated polyp with abnormalities of architecture and proliferation but lacking the classic features of epithelial dysplasia (intraepithelial neoplasia)	Right colon	Frequent BRAF mutation (75%-82%) and CIMP (92%)
Sessile serrated adenoma with cytological dysplasia	Mixed polyp	Rare serrated polyp that includes two separate components: Nondysplastic (usually SSA) and either traditional adenoma or serrated adenoma	Right and left colon	Frequent BRAF mutation, (89%)
Serrated adenoma	Mixed hyperplastic adenomatous polyp; Atypical hyperplastic polyp; TSA	Relatively rare neoplastic polyp having a serrated architecture reminiscent of hyperplastic polyp but with unequivocal traditional adenomatous dysplasia; Comprises < 5% of serrated polyps	Left colon	Marked molecular heterogeneity; May have either KRAS or BRAF mutation

SSA: Sessile serrated adenoma; TSA: Traditional serrated adenoma; CIMP: CpG island methylator phenotype.