The use of fine needle aspirates in the evaluation of progesterone receptor content in breast cancer.

Material obtained by fine needle aspiration (FNA) from 30 surgically removed breast carcinomas was tested for the immunocytochemical localization of progesterone receptor (PR) using a monoclonal antibody (MAb) developed against human breast cancer PR. When compared to values obtained by conventional biochemical analysis of cytosol protein in the same tissue, a semiquantitative relationship suggested that a high intensity (3+) stain in cases in which more than 30% of the cells were positive was compatible with a PR concentration of greater than 200 fmol/mg. An absence of nuclear stain was indicative of a PR concentration of less than 10 fmol/mg, while a stain of an intermediate intensity (2+) or a stain of high intensity (3+) in less than 30% of the cells correlated with a PR level of 51-200 fmol/mg. Only one case in this group showed weak staining with a PR concentration of 85.5 fmol/mg. Cases containing a low concentration of PR (less than 50 fmol/mg) demonstrated a weak nuclear stain (1+) in less than 10% of the cells. Localization of nuclear PR by MAb staining of FNA cytologic specimens affords a relatively simple, inexpensive method of obtaining potentially significant information regarding tumor response to hormonal therapy and the recurrence potential of a tumor in patients with primary breast cancer; at the same time, this technique obviates several important disadvantages of conventional biochemical analysis.