The possible role of stromal influences in tumor cell heterogeneity. Histology and fibronectin pattern of the Yoshida sarcoma of the rat.

Yoshida tumors implanted subcutaneously in the rat are conspicuously heterogeneous. A definite zoning can be discerned. Cell nuclei range from uniform epitheloid (type I) via pleomorphic (type II) to compact (type III). Type III is seen to detach at the rim of the tumor and to infiltrate the dermis. Type I is characterized by positive pericellular fibronectin staining, type II and III are fibronectin-negative. A marked spatial relationship was seen between types II and III on one hand and the presence of collagenous stroma on the other. It is conjectured that stromal components play a role in tumor promotion or progression.