Comparison of two methods of storing breast fine needle aspirates (FNAs) using oestrogen receptor immunocytochemical assay as a method of evaluating the storage methods.

Two methods of storing fine needle aspirates were compared in 14 patients with breast cancer. The methods of storage were: (1) as a Cytospin slide prepared immediately from the aspirated material and stored at -80 degrees C; (2) as a suspension of cells in tissue culture medium, stored at -80 degrees C. The effect of storage on the cells was assessed by means of an oestrogen receptor immunocytochemical assay (ER-ICA). An ER positivity of 100% was obtained by ER-ICA staining of cells after storage method 1, whilst all of the specimens stored by method 2 were ER-negative. The data demonstrate that cells stored in tissue culture medium at -80 degrees C are not suitable for ER measurement. The storage method of choice for specimens intended for ERICA is as a Cytospin slide. The ER status of cells deposited on Cytospin slides prepared immediately and stored at -80 degrees C for 2 years could be demonstrated despite the delay in processing the specimen.