Lymphatic vessels in colorectal cancer and their relation with inflammatory infiltrate.
OBJECTIVE
The aim of this study was to determine why colorectal tumors confined to submucosa rarely metastasize. Under normal conditions, the submucosa contains many large lymphatic vessels with thin walls that would presumably favor the spread of cancer cells through the lymphatic system.


METHODS
Specimens of colorectal cancer tissue, the border between tumor and normal tissue, and normal tissue were obtained from patients undergoing radical resection of colorectal cancer. The material was embedded in methacrylate resin for light microscopy and Epon for transmission electron microscopy examination. Light microscopy observations were routinely performed on serial sections.


RESULTS
No lymphatic vessels were ever found in the tumor mass. The border area contained peritumoral inflammatory infiltrate of variable thickness. Where submucosal lymphatic vessels came into contact with peritumoral inflammatory infiltrate, they were profoundly altered: their endothelium was fragmented, and their walls were disrupted. These altered lymphatic vessels were almost always accompanied by mast cells, which were observed in the process of degranulating toward the lymphatic endothelium. No such alterations were detected in blood vessels.


CONCLUSIONS
Our results suggest that mast cells, probably influenced by inflammatory infiltrate and/or colorectal cancer cells, destroy lymphatic vessels, which prevents cancer cells from spreading through the lymphatic system.
Sacchi
Giovanni
G
Dipartimento di Neuroscienze, Sezione di Medicina Molecolare, University of Siena, Siena, Italy.
Weber
Elisabetta
E
Aglianó
Margherita
M
Lorenzoni
Paola
P
Rossi
Antonella
A
Caruso
Anna Maria
AM
Vernillo
Remo
R
Gerli
Renato
R
Lorenzi
Marco
M
D000368:Aged; D000369:Aged, 80 and over; D015179:Colorectal Neoplasms / Q000473:pathology* / Q000648:ultrastructure; D005260:Female; D006801:Humans; D008207:Lymphatic Metastasis / Q000648:ultrastructure; D008208:Lymphatic System / Q000473:pathology* / Q000648:ultrastructure; D008297:Male; D008407:Mast Cells; D008854:Microscopy, Electron; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging