In vivo demonstration of cytoplasmic fibronectin in human breast carcinomas.

The distribution pattern of fibronectin in 24 invasive human breast carcinomas has been studied using the indirect immunoperoxidase technique. A positive cytoplasmic staining reaction was observed in 16 tumours. Well-differentiated carcinomas showed weak or no staining, whereas all moderately or poorly differentiated carcinomas and one signet ring cell carcinoma contained fibronectin positive tumour cells with moderate or strong staining. The staining intensity was positively correlated to degree of anaplasia with the exception of two moderately differentiated duct carcinomas and the two medullary carcinomas, which were only slightly positive. Non-attached independently growing tumour cells stained more intensely than tumour cells in clusters. Pericellular fibronectin was found in only one carcinoma of medullary type. In normal ducts and glands it was seen at the stromal-epithelial junction corresponding to the basement membrane, around myoepithelial cells and along the luminal border. The results support the findings of several in vitro investigations that breast tumour cells synthesize fibronectin. It also suggests that cytoplasmic fibronectin expression might be an indicator of tissue differentiation in non-solidly growing invasive duct carcinomas of the human mammary gland.