en Internal Medicine & Gastroenterology Internal Medicine & Gastroenterology Original Research Original Research In human breast cancer, estrogen receptor (ER) status of the tumor has prognostic and therapeutic significance. However, facilities to study ER are not widely available to us. We postulated that if there is a correlation between histologic grade and ER status of invasive ductal carcinoma (IDC), it may help predict the ER status of the tumor. Of 8 4 cases of breast carcinoma referred to the Cancer I:q.stitute of Tehran for immunohisto logic study of ER in 1995, 69 cases of IDC that had adequate H & E stained slides were chosen. Using the Nottingham modifi. cation of the Bloom-Richardson grading system of IDC, all cases were scored by each of us separately. Conflicting cases were jointly reassessed until a consensus was reached. Sections of paraffin blocks were stained for ER using the avidinbiotin complex method and then they were assessed by a digital image analyzer. There was an inverse relationship between ER positivity of tumors and each of the grading parameters and the•ultimate grade that were all statistically significant (p<0.0001). Moreover, further analysis revealed that low histologic grade (with scores of3 or 4) had a 92.3% positive predictive value (range 62.9%-98 .2%) for ER positivity. Similarly, histologic grade-=-in the presence of score 3 nuclei-had an 83.9% positive predictive value (range 71.2%-91.9%) of ER negativity in tumor cells. These findings suggest that in tumors with histologic grades at both ends of the spectrum, ER status may reliably be predicted in a significant number of cases. Breast carcinoma, invasive ductal carcinoma, estrogen receptor, histologic grading. 133 135 http://mjiri.iums.ac.ir/browse.php?a_code=A-10-298-330&slc_lang=en&sid=1 F TIRGARI 20031947532846004424 20031947532846004424 Yes From the Cancer Institute, Tehran University of Medical Sciences, Tehran, ALI ZARE MEHRJARDI 20031947532846004425 20031947532846004425 No Kerman University of Medical Sciences, Kerman, I.R. Iran GUITY IRAVANLOO 20031947532846004426 20031947532846004426 No From the Cancer Institute, Tehran University of Medical Sciences, Tehran,