Differentiation between metaplastic carcinomas and sarcomas of the human female breast by fibronectin

The distribution pattern of fibronectin in metaplastic carcinomas, stromal sarcomas, malignant cystosarcoma phyllodes tumours and histiocytic type lymphomas of the human female breast has been studied using the indirect immunoperoxidase technique on formalin fixed paraffin embedded tissue. Fibronectin was demonstrated as intensely stained strands between tumour cells forming an irregular network in metaplastic carcinomas and lymphomas. Stromal sarcomas and the malignant stromal component of the phyllodes tumours exhibited, in contrast, a uniform staining throughout tumour cells and stroma which was weaker than in adjacent normal-looking connective tissue. We suggest that the intense staining reaction of metaplastic carcinomas is due to the scirrhous reaction generally associated with invasive human breast carcinomas. The advantage of using fibronectin as a diagnostic tool in the differentiation of carcinoma/lymphoma versus sarcoma is the fact that the antigen is a stromal marker and its staining intensity is not influenced by the morphology or degree of differentiation of non-mesenchymal tumours.