Comparison of Estrogen Receptor Immunostaining in Papanicolaou-Stained Direct Smears and Matched Cell Block Sections
Rhonda A Burch-Smith, Linda Payne, Anirban Bhattacharyya, Karla Valencia, Janet Quinones, Michael Deavers, Savitri Krishnamurthy. UT MD Anderson Cancer Center, Houston, TX
Background: Cell block (CB) is the optimal cytologic specimen for evaluating estrogen receptor (ER) in patients with breast carcinoma. The need for ER immunostaining (IS) of Papanicolaou (Pap)-stained direct smears (DSs) arises in patients with breast carcinoma when CBs cannot be prepared because of limited cellularity of the aspirate. The primary objective of our study was to compare the IS of Pap-stained DSs with corresponding formalin-fixed and paraffin-embedded CB sections.
Design: The study included 68 matched specimens of Pap-stained DSs and CBs from 18 effusions with metastatic breast carcinoma and 16 scrapes of surgical specimens of breast carcinoma (34 cases). Immunostaining for ER was performed using a polymeric biotin-free horseradish peroxide (HRP) method on (Leica Microsystems, Bannockburn, IL) using anti- ER antibody (Clone ER 6F11, dilution 1:35, Novocastra) with antigen retrieval (citrate buffer). The proportion of ER nuclear positivity in the tumor cells was expressed as a percentage and categorized as low positive (LP) (1% to 9% ER +) or as positive (≥10% ER +); intensity was scored on a scale of 1-3. Comparison of the ER IS of DS and CB was performed using the kappa statistic.
Results: The DSs and CBs demonstrated positive ER IS in 24 (71%) DSs and 26 (76%) CBs, and were negative in 10 (29%) DSs and 8 (24 %) CBs. The DSs were positive for ER in 22 specimens and LP in 2, whereas the CBs were positive in 24 specimens and LP in 2. Except for one DS, the proportion and intensity of IS was higher in DSs than in CBs. There were concordant results for ER IS in 30 (88%) of the 34 cases. We found discrepant results in 4 cases (12%); 3 DSs with negative results where the CBs showed positive IS (20%, 1+; 10%, 2+; 50%, 1+) and 1 DS with low positive (1%, 1+) ER with negative results on CB. Comparison of DSs with CBs revealed a kappa statistic of 0.70, which indicates substantial agreement.
Conclusions: 1. Pap-stained DSs were comparable to CBs for ER IS.
2. The proportion and intensity of ER IS was higher in DSs than in CBs.
3. Discrepant cases mainly consisted of negative results in DSs corresponding to weakly ER-positive CBs.
4. Whereas DSs positive for ER expression indicate true positives, a negative result may represent either a true-negative or false-negative result.
Tuesday, March 20, 2012 9:30 AM
Poster Session III # 83, Tuesday Morning