Background: Estrogen receptor (ER) status and progesterone receptor (PgR) status are strong prognostic and predictive markers in breast carcinomas. Steroid receptors are fragile and optimal handling of both cytological and histological material, including fixation, is crucial. Liquid based material offers the possibility to prepare a number of slides from one lesion and is increasingly being used for immunocytochemistry. It also offers the possibility to prepare several smears and to store these at different temperatures as well as storing residual material in the liquid.
Materials and methods: The samples consisted of fine needle aspirate material from 53 breast carcinomas. Direct smears and liquid based preparations were used in parallel for immunocytochemical detection of ER and PgR receptor status. Slides from liquid suspensions were stored at -20°C and -74°C for 3 and 6 months, respectively. Direct smears were fixed primarily in 4% formalin. Liquid based specimens were post-fixed in 4% formalin. All specimens were subjected to microwave-stimulated epitope retrieval. Antibody concentrations were ER 1:150 and PgR 1:200 for both preparation methods. The immunostaining program was identical for both the methods.
Results: Liquid based specimens had a statistically non-significant higher percentage of positive cases compared to direct smears. Specimens prepared from liquid suspensions and stored at -20°C and -74°C for 3 and 6 months, respectively, showed a virtually unchanged ER and PgR reactivity (P = 0.002).
Conclusions: Liquid suspensions and liquid based slide preparations seem to offer an optimal pre-fixation and preservation of ER/PgR in breast carcinoma cells. Post-fixation with 4% formalin followed by microwave-stimulated epitope retrieval before immunostaining is recommended. Long-time storage of liquid based specimens at -20°C or -74°C for at least 6 months without significant loss of immunoreactivity is feasible. They may be used as internal positive and negative controls.
Keywords: Breast carcinoma; estrogen receptor; fine needle aspiration cytology; liquid based preparation; long-time storage.