The Pattern of the IHC Based Molecular Classification of Breast Cancer

Breast cancer (BC) is heterogeneous in its presentation, showing marked diversities spanning its morphological features, clinical outcomes, intrinsic subtypes and prevalence patterns. Morphologically, identical tumours can display divergent clinical outcomes. This can predominantly be attributed to molecular class differences that exist amongst the histologically similar types. Molecular analysis of breast cancer might lead to novel predictive tests that could help selection of the most effective adjuvant therapy for each individual. Molecular classes are luminal tumours being categorized by hormone receptor (HR) positivity, Human epidermal receptor (HER2) expression a feature of Human epidermal receptor (HER 2) tumours, and cytokeratin (CK5/6) and/or epidermal growth factor receptor (EGFR) indicative of basal-like tumours.
Aim of the study:-Molecular classification of breast cancer by using Immunohistochemistry (IHC) to evaluate the expression of Estrogen Receptors (ER), Progesterone Receptors (PR), Human epidermal receptor (HER2/neu), Epidermal growth factor receptor (EGFR) and cytokeratin (CK5/6), To investigate the expression of P53 and Ki67 and to study their correlation with previously studied as prognostic markers. Digimizer software used for image analysis of immunohistochemical expression of these markers. Patients and Methods:- Sixty four females cases with breast cancer with mean of age =46.22 and median 46y.. Their age ranged from (21- 67) years old were included in this study. They were attendants of Al –Kadhimiyia teaching hospital and Medical city hospital in Baghdad and from private laboratory in Baghdad in the period between 2010 to 2011compared with twenty female normal breast tissue samples were taking from normal tissue around biopsies taken during lumpectomies in benign breast diseases. From each block, eight sections of 5µm thickness were taken, one section was stained with H&E and the other seven sections were immunohistochemically stained for ER, PR, HER2, CK5/6, EGFR, P53 and Ki67. Computerized digital analysis by using digimizer software was utilized for image analysis of immunohistochemical expression of various markers in both malignant and healthy tissues. Results:- In current study ER showed significant differences, in terms of Intensity, between control and breast carcinoma groups with p-values <0.05. Ck5/6 showed significant differences, in term of Intensity, between control and breast carcinoma groups with p-values <0.05. PR showed no significant differences, in term of Intensity, between control and breast carcinoma groups with p-values >0.05. According to molecular classification Majority of cases were Luminal A subtype (52%), 28% of cases Luminal B subtype, 8% HER2 enriched subtype, 9% Basal-like subtype and 3% unclassified subtype. non-significant correlations in molecular types LA, LB, Basal, HER2/neu, and unclassified with age P-value > 0.05. Luminal-like cancers represent the highest proportion (80%).The luminal subtypes were mainly medium grade (72.72% for luminal A and 61.11% for luminal B). Luminal tumors, both A and B, express hormone receptors, but these two luminal subtypes present distinguishing characteristics. Luminal A cancers have a high expression of ER and PR, HER2-negative;the highest proportion of stage I–II (81.82%) and moderately differentiated lesions (72.72%). The patients were ages a mean of 47.09 years. Luminal B cancers (28%) have a lower expression of ER and PR with HER2-positive. Patients with luminal B subtype tumor were between the same age limits, but younger than those with luminal A subtype, mean age being 46.28 years. Luminal B cases have shown poorly differentiated cancers, in a larger percentage than luminal A cases, Luminal B cases have shown lymph node involvement in a larger percentage than luminal A cases and Luminal B cases have shown Ki67 and P53 expression in a larger percentage than luminal A cases. The basal-like cases were patients’ age with an average of 47.33 years. This type was displays aggressive features, such as large size tumor 33.33% <5 cm., poorly differentiated cancers33.33% grade III and stage III . 50% of cases were invasive ductal carcinomas and 83% presented nodal metastasis at the time of diagnosis. The HER2 subtype is more likely to be high-graded and poorly differentiated 40% , 60% in stage III, and more likely to involve axillary lymph nodes (100%). Age of patients were a mean age of 41.40 years. All five tumors of HER2 subtype were histologically invasive ductal carcinomas and had high expression of Ki67 and P53. In our study, only two cases were framed in unclassified cancers type, moderately/poorly differentiated. All cases are of ductal invasive type (100%). All tumor size between 2-5cm and all cases were negative for Ki67 (100%) expression but equally express P53 (50%).There were correlation significant (P value <0.05) in PR (DLI) and HER2 (DLI) with molecular subtype. There were significant correlation in Ki67 with type of tumor with P-value <0.05. Significant correlation in P53 with grade of tumor with P-value <0.05 but there is no significant correlation with Ki67. There was significant relation between the immunohistochemical expression of p53 and EGFR. (P=0.032) and significant relation between the immunohistochemical expression of Ki67 and PR. (P=0.013). There was significant relation between the immunohistochemical expression of Ki67 and P53. (P =0.019).
Conclusion:- According to the results of current study, breast cancer in Iraqi women can be classified to five subtype and classify each type in to good and bad prognosis by prognostic marker P53 and Ki67.