Fluorescent location of tumour cells in fine needle aspirates.

Cells obtained by fine needle aspiration of breast lumps were spread onto microscope slides, defatted with xylene and stained with a fluorescent probe for a cell surface protease. In these aspirates, carcinoma cells possess an active cell surface protease, guanidinobenzoatase (GB), very similar to plasminogen activator (1), which binds the fluorescent probe as a competitive inhibitor. Cells obtained from benign and normal breast lack this active GB and can be distinguished easily from the carcinoma cells by fluorescent microscopy. We use this simple technique to examine breast lumps containing carcinoma cells and to demonstrate the similarity of GB on these carcinoma cells to tissue type plasminogen activator (t-PA).