Emergence of adenomatous aberrant crypt foci (ACF) from hyperplastic ACF with concomitant increase in cell proliferation.

To investigate the relationship between aberrant crypt foci (ACF) and colon neoplasia in colorectal carcinogenesis, we evaluated 433 ACF, which were collected from the grossly normal mucosa of surgical specimens from 57 patients with colorectal cancer. The ACF ranged in size from 3 to 412 aberrant crypts/focus. Large ACF (> or = 50 crypts/focus) comprised 25% of the total ACF studied. Histopathologically, 65% (67 of 103) of large ACF were diagnosed as hyperplasia, 10% (10 of 103) as adenoma, and 1% (1 of 103) as within normal colorectal mucosa. The remaining 24% (25 of 103) were diagnosed as "stage I abnormality crypts," which were characterized by their extension of the proliferative compartment to the surface of crypts but with no changes in the major site of proliferation, as designated by E. E. Deschner [Pathol. Annu., 18 (Part 1): 205-219, 1983]. Of the 25 stage I abnormality ACF, 7 ACF coexisted with hyperplasia. Of 10 adenomatous ACF, two coexisted with stage I abnormality crypts. A K-ras codon 12 mutation was identified in 85% (93 of 109) of large ACF. The proliferative activity of stage I crypts was significantly higher than that of hyperplastic crypts in the same ACF. These observations suggest that some hyperplastic ACF may develop into adenomatous ACF by way of stage I abnormality ACF with concomitant acquisition of higher proliferative activity through some genetic and/or epigenetic changes.