metallothionein and Colonic-Polyps

Metallothionein (MT) expression is observed in various carcinomas, but its role is not fully understood. To clarify the clinicopathological significance of MT, 87 colorectal adenomas and 128 early-stage carcinomas were immunohistochemically analysed for MT expression. The degree of MT immunostaining of a specimen was graded according to the proportion of MT-positive cells; negative (<5%) and positive (focally 5-50%, diffusely >50%). MT expression significantly decreased with tumour development. For carcinomas, MT-positivity was significantly associated with depth of invasion (T1 60% versus T2 33%; P<0.01), vascular involvement (positive 35% versus negative 61%; P<0.01) and morphology (polypoid 62% versus depressed 26%; P<0.01). Regarding MT-positive distribution, the diffuse-positive rate in MT-positive polypoid lesions was 28%, while MT-positive depressed lesions were all diffusely stained (P<0.01). In conclusion, our results suggested that decreasing MT expression is an early event in colorectal carcinogenesis and may reflect local invasion. Furthermore, MT-positive distribution may reflect genetic differences between the polypoid and depressed-type.

Topics: Adult; Aged; Aged, 80 and over; Colonic Polyps; Colorectal Neoplasms; Female; Humans; Immunohistochemistry; Intestinal Mucosa; Male; Metallothionein; Middle Aged; Neoplasm Proteins; Proliferating Cell Nuclear Antigen