Retrospective c‐erbB‐2 immunostaining in aspiration cytology of breast cancer

Fifty fine-needle aspiration cytologies of breast that were diagnosed as carcinomas were retrieved from the files and retrospectively evaluated for the expression of c-erbB-2 oncoprotein using standard immunocytochemical methods. Corresponding histologic sections of all tumors were similarly studied. Seventeen fine-needle aspirates (34%) reacted positively for the presence of c-erbB-2 oncoprotein. All but one (32%) of the corresponding tissue sections were also positive for c-erbB-2 by immunohistochemistry. All positive cases were infiltrative ductal carcinomas with a preponderance of the comedo type. Positive reactions were localized in the cytoplasmic membrane of tumor cells. The staining was either present in all cells throughout a tumor, or it was completely absent. We conclude that immunocytochemistry for c-erbB-2 oncoprotein can be performed on fine-needle aspiration cytology samples that are previously fixed and stained with the Papanicolaou technique. Furthermore, the sensitivity of immunostaining results are comparable to that obtained in histologic sections.