IMAGE-ANALYSIS QUANTIFICATION IN HORMONE-RECEPTOR ASSAY OF MUCINOUS CARCINOMA OF THE BREAST - COMPARISON WITH BIOCHEMICAL-ANALYSIS

Mucinous carcinoma (MC) of the breast is characterized by abundant ext racellular mucin and by variable epithelial cellularity. Since some MC s are extremely hypocellular, we questioned the validity of biochemica l (BIO) assays in these tumors. We analyzed parffin-embedded tissue fr om 34 cases of MC of the breast for quantitative estrogen receptor (ER ) and progesterone receptor (PR) using immunohistochemistry (IHC) on t he Cell Analysis System GAS-200. Of the 34 cases, 31 (91%) were positi ve for ER, whereas 18 (53 %) were positive for PR. In 21 cases the qua ntitative ER and PR were assayed biochemically by a dextran-coated cha rcoal method. Using the BIO results as the ''true'' values, the sensit ivity of IHC for ER and PR was 100% and 78%, and the specificity tons 13% and 64%, respectively. The low specificity of the values obtained by IHC was attributed to the fact that eight cases were ''falsely'' fa lse positive (negative by BIO and positive by IHC) for ER and/or PR. R eview of the histologic patterns of all 21 cases showed that 7 of the 8 falsely false positive cases were significantly hypocellular (epithe lial cellularity 5-20%) as compared to the remaining cases (epithelial cellularity 20-75%). We conclude that immunohistochemical analysis of ER/PR status using image analysis in MC is a sensitive method, with t he ability to detect receptor content when their concentration might b e too low to be demonstrated by the conventional method as a result of sparse cellularity.