Table 1.

Endoscopic, Histologic, and Molecular Features of Sessile Serrated Adenoma/Polyps

	Endoscopic	Histologic	Molecular
Nondysplastic	Flat (0-IIa/0-IIb) morphology Pale colour, indistinct borders Mucous cap, surrounding rim of debris/stool Type II-0 pit pattern	Saw-toothed architecture of crypt epithelium Boot shaped crypts +/− goblet/mucinous cells at base Pseudoinvasion	BRAF V600E mutation CIMP-high MLH1 promotor methylation KRAS mutations (infrequent)
Dysplastic	Transition from flat to nodular, sessile or depressed area Type III–V pit pattern NICE 2, Sano II on NBI	Adenomatous dysplasia* (most common) Serrated dysplasia† (less common)	Reduced expression of MLH1 Microsatellite instability Silencing of other tumor suppressor genes‡

CIMP, CpG island methylator phenotype; NICE, narrow band imaging (NBI) international colorectal endoscopic classification.

^*Characterized by elongated penicillate nuclei with hyperchromasia, nuclear pseudostratification and amphophilic cytoplasm;³

^†Characterized by cells with a more cuboidal shape and eosinophilic cytoplasm, enlarged vesicular nuclei and prominent nucleoli;³

^‡Including p16INK4a, IGFBP7 and MGMT.⁴