Evaluation of Number Density of Tumor-Associated Macrophages by Immunohistochemistry and Semiquantitative Scoring in Invasive Breast Cancer: An Indian Study.

Abstract

Tumor microenvironment is emerging as a critical factor for progression of breast cancer. Tumor-associated macrophages (TAMs) play an important role in promoting tumor growth. This study was aimed at correlation of number density (ND) of TAMs with invasive ductal carcinoma (IDC) grading utilizing an image morphometric technique. We also sought to compare the TAMs and ND in the tumoral area and stromal region. We also explored the relationship between the clinical and pathological prognostic parameters. The study included 75 cases of IDC that had undergone modified radical mastectomy. The Institutional Ethics Committee approved the study. Samples were classified as Grade 1, 2, and 3. Cases were graded as per the modified Bloom and Richardson criterion. Mean with standard deviation was calculated for each group. We utilized CD68 and CD163 immunostained sections for determining the ND of TAMs. TAMs were evaluated using computerized digital photomicrograph system with image analyzing software. ND was defined as the number of TAMs in total number of TAMs in five high-power fields/total area of five fields. ND was calculated separately in tumor and tumor stroma (TS). Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2/neu (HER2/neu) were scored in accordance with recommendations. Ki-67 was scored as per the recommended guidelines. Data were tabulated in Microsoft Excel. SPSS version 20.0 (IBM Corp., Armonk, NY, USA) was used for statistical analysis. To determine the relationship between macrophage density and clinicopathologic parameters, we used the independent t-test. To determine the differences in the parameters, analysis of variance (ANOVA) was utilized. Age of the patients ranged from 34 to 58 years (mean: 55.5). One-way ANOVA between various grades of tumor indicating significant differences in terms of CD68 and CD163 densities in tumor and stroma (P < 0.0001). i.e., significant increased density of CD68 and CD163 was observed in Grade 3 tumor as compared to other two groups. A greater histological grade, ER, PR negative status, and a high Ki-67 index were all associated with TAM ND. There was no relation to HER2/neu status. Result of unpaired t-test indicates increased density in stroma as compared to tumor among various grades of IDC. We analyzed images with a software using photographs of the stained slides. This helped in quantitative analysis of TAMs on the CD68 and CD163 stained sections. This approach standardizes and reproducibly counts TAMs per unit area. We found significant difference between the number densities of TAMs in grades of invasive breast carcinoma. There were statistically significant differences in numerical densities of TAMs with ER, PR negativity, and Ki-67. There was no correlation with HER2/neu. Densities of CD68 and CD163 densities are more prevalent in TS as compared to intratumoral region.