Non-polypoid adenomas of the colon are associated with subjacent lymphoid nodules. An experimental study in rats.
BACKGROUND
Subjacent lymphoid nodules (SLNs) have been found in 38% of non-polypoid colonic adenomas in humans. In the present work the presence of SLNs in experimentally induced colonic adenomas was investigated in rats.


METHODS
1,2-Dimethylhydrazine was injected subcutaneously in 290 Sprague-Dawley rats for 27 weeks.


RESULTS
An SLN was present in 28.6% of the 84 adenomas, in 8.4% of the 119 adenocarcinomas, and in 9.7% of the 31 small carcinomas without remnant adenomatous tissue. An SLN was found in 35.6% of the 59 non-polypoid neoplasias but only in 9.1% of the 175 polypoid (that is, exophytic) neoplasias. When only adenomas were considered, SLNs were present in 50.0% of the 34 non-polypoid adenomas but only in 14.0% of the 50 polypoid adenomas.


CONCLUSIONS
Non-polypoid colonic adenomas evolve preferentially from the minimal fraction of the colonic mucosa that overlays the few existing lymphoid nodules in rats.
Rubio
C A
CA
Dept. of Pathology, Karolinska Institute, and Clinic of Gastroenterology and Hepatology, Karolinska Hospital, Stockholm, Sweden.
Shetye
J
J
Jaramillo
E
E
D000236:Adenoma / Q000473:pathology*; D000818:Animals; D003110:Colonic Neoplasms / Q000473:pathology*; D005260:Female; D008221:Lymphoid Tissue / Q000473:pathology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley