Pathological characteristics of triple negative breast cancer phenotype in a cohort of Sri Lankan females

Introduction: Breast cancer is the commonest cancer among Sri Lankan women. Triple negative is a type of breast cancer that is negative for expression of oestrogen receptors (ER), progesterone receptors (PR) and human epidermal growth factor 2 receptors (HER 2). Objective: To identify the pathological characteristics of triple negative breast cancer phenotype in a group of Sri Lankan women. Method: 200 cases of diagnosed breast cancers were analysed to determine the prevalence of triple negative breast cancers. All the slides were re-examined histologically to find out whether there were specific morphological features in the triple negative group when compared with the ER/PR positive HER 2 negative group, ER/ PR negative HER2 positive group and ER/PR positive HER2 positive group. Department of Cellular Pathology, Wycombe Hospital, Buckinghamshire Healthcare NHS Trust High Wycombe, Buckinghamshire, United Kingdom1, Department of Pathology2, Faculty of Medicine, University of Peradeniya, Sri Lanka, Correspondence : G V S Wathuge, Department of Cellular Pathology, Wycombe Hospital, Buckinghamshire Healthcare NHS Trust, High Wycombe, Buckinghamshire HP11 2TT, United Kingdom E mail: gayathrivasana@hotmail.com Paper Journal of Diagnostic Pathology 2015;10(2):21-31 Paper Pathological characteristics of triple negative breast cancer phenotype in a cohort of Sri Lankan females G V S Wathuge1, N V I Ratnatunga2 21 Results and conclusion: The prevalence of triple negative breast cancer in the study group was 36%. The mean age affected by this tumour category was 49.5 years. The commonest age group affected was 41-50 years. The commonest histological type in all categories was invasive ductal carcinoma. A significant number of triple negative tumours were histologically Grade 3 compared to the ER/PR positive HER2 negative group. The mean tumour size was 2.73 cm. Although the percentage of triple negative tumours among the lymph node stages was similar, a statistically significant number of triple negative tumours was in stage 3 and showed tumour necrosis. The triple negativity was also associated with a lymphocytic reaction at the host tumour interface and infiltrative margins. Triple negative status showed a negative association with skin and nipple invasion, lymphovascular invasion and an insitu component.


Introduction
Breast cancer is the commonest cancer among Sri Lankan women. 1 Triple negative breast cancer is a specific subtype of breast cancer, so called because the tumour cells are negative for expression of oestrogen receptors (ER), progesterone receptors (PR), and human epidermal growth factor 2 receptor (HER 2 ) proteins.They do not respond to endocrine therapy and Herceptin as the required receptors are not expressed in them.The only treatment option available currently is chemotherapy. 2,3ese cancers occur more commonly in young (<40years), African American women 4 and show an aggressive behaviour and poor survival rates 5 .The prevalence is about 15% in the world 6 .The range in some studies is 10-20%.6 In Sri Lanka the prevalence was 28.23% according to a study done in 2007 7 .
The so called 'basal-like' breast cancers are also triple negative and they arise from the outer myoepithlial or basal cell layer of the duct epithelium and express a unique basal like (basal layer/myoepithelial-like) molecular profile and morphological characteristics. 2,8They are positive for basal cytokeratins such as CK 5/6, CK 14, CK17 and EGFR and are more common in BRCA 1 carriers. 3,9The morphological features include invasive ductal carcinoma like features 10 and presence of other features such as medullary carcinoma-like features and metaplastic elements such as spindle cells and squamous elements.Other features include a high grade (Grade 3), a central scar, pushing growth patterns, geographic or comedo type necrosis with two distinct growth patterns including a solid sheet like growth and a trabecular arrangement. 5,10Many of these tumours show frequent apoptotic bodies, scanty stromal content and glomeruloid microvascular proliferations. 11The triple negative phenotype significantly correlates with tumour size, histological grade, lymph node status, P 53 expression and EGFR according to a study done in China. 12 is also documented that identifying "basal like" tumours as a distinct entity has a real clinical significance because there are several associations that are opposite to those observed for luminal group of cancers 10 .More importantly, brain metastases are more common than bone metastases 10,13 in these tumours.
Therefore, it is important to document the status of triple negative phenotype in Sri Lanka to decide on targeted therapy. 3

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To determine the prevalence of triple

Methods
The material consisted of two hundred breast carcinomas referred for receptor status analysis.The morphology of the tumour was studied with haematoxylin and eosin stained sections.
Staining for ER, PR and HER2 was done using DAKO monoclonal antibodies and a three stage system.Semi quantitative scoring of ER and PR was done using the Quick Allred Score (0-8), and a total score of more than 2 was taken as being positive for both in this analysis. 9 HER2 amplification was scored according to the guidelines given in pathology reporting of breast diseases NHSBSP publication no 58, January 2005.A score of +3 was taken as being positive and +2 was taken as borderline. 9The slides were interpreted independently by the two authors, and a consensus reached if there was a discrepancy.

Results and interpretation
The percentage prevalence of triple negative breast cancers (Group A) was 36% compared to Group B -47.5%, Group C -9%, and Group D -7.5% (Table1).A 7.77% increase in the percentage of triple negative breast cancers was noted compared to 28.23% previously reported in a Sri Lankan study 7 .
Moreover, the prevalence of triple negative breast cancers in our study group is more than double that of the world average prevalence. 6is higher prevalence of triple negativity raises the possibility of technical errors or a higher Grade 3 tumours were significantly higher in group A compared to group B (Table 3) (p value = 0.000).These results were in keeping with the results of the other studies and the study done in China. 10,12 oreover, the percentage of grade 1 tumours is considerably less within Group A (Table3).However, all four groups showed highest percentage of Grade 2 tumours (Table 3).In the Nottingham grading system, a high histological grade reflects a high mitotic count, high degree of nuclear pleomorphism and lack of tubule formation. 14,15These are also features of the basal-like tumours.The mean tumour size at diagnosis for group A was 2.73 cm.A statistically significant difference was not seen in the tumour size among the four categories when the Chi square test was applied for analysis.(Table 4).Therefore, the triple negative status does not significantly correlate with the tumour size, a finding which is contradictory to the results of the Chinese study. 12There was no statistically significant difference in the type of tumour margin between group A and groups B or groups A and C (p values 0.115 and 0.339 respectively).Statistical analysis was not possible between groups A and D due to lack of samples in category 1 of group D. All the groups showed a high percentage of infiltrating margins (Table 4).Tumours with pushing margins are known to have a better prognosis than tumours with infiltrating margins. 14e presence of tumour necrosis was significant in group A compared to group B (p value = 0.001).This could be due to the fact that some tumours in group A were basal like tumours, where geographic areas or comedo type necrosis are a characteristic feature 5,10 However, groups C and D did not show a significant difference to group A with regard to necrosis (p values 0.431 and 0.597 respectively) (Table 4).All four groups did not have a high percentage of skin and nipple invasion (Table 5).
It has been found that tumours with an absence of an inflammatory reaction at the periphery have a lesser degree of nodal metastases and presumably a better prognosis, the only exception being medullary carcinoma 14 .
In our study, all four groups showed a higher percentage of tumours with a lymphocytic reaction at the host-tumour interface (Table 5).
This finding is a bad prognostic factor for triple negative and other types of cancers such as medullary carcinomas which were not included in the 200 cases analysed.
The presence of tumour emboli in lymphatic vessels within the breast is associated with an increased risk of tumour recurrence. 14esence of tumour emboli has shown a high correlation with tumour size, histological grade, tumour type, lymph node status, development of distant metastasis and a poor prognosis. 14l four groups showed a higher percentage of tumours without lympho-vascular invasion (Table 5).This is a good prognostic factor observed in the triple negative group.Also the difference was not statistically significant when The amount of in-situ component correlates with the incidence of multicentricity and indirectly with the probability of occult invasion. 14It is also reported that sometimes in-situ ductal malignancies of the comedo carcinoma type can be associated with metastases in the absence of detectable invasion. 14Therefore, the presence of an in-situ component is associated with an unfavourable prognosis.
Our results showed a negative association of all four groups with the occurrence of an in-situ component and thus a better prognosis (Table 5).

Paper
negative breast cancers ( Group A) in Paper Journal of Diagnostic Pathology 2015;10(2):21-31 a cohort of breast cancer patients and compare it to the prevalence of ER/PR positive and HER 2 negative cancers (Group B), ER/PR negative and HER 2 positive cancer group (Group C) and ER/ PR positive and HER 2 positive cancer group (Group D) • To determine the age distribution in group A and compared to groups B C and D • To determine the pathological characteristics of group A with special reference to basal like morphological features • To determine the occurrence of such pathological characteristics in group A compared to the other groups (B, C and D) were the histological type, histological grade (Nottingham), tumour size at diagnosis, invasion of nipple and skin, lymph node stage, infiltrative or pushing tumour margins, a lymphocytic reaction at the host tumour interface, presence of lymphovascular invasion, an associated in-situ component and the presence of tumour necrosis.
group A was compared with groups B, C and D (p values 0.754, 0.705 and 0.138 respectively in chi square test).

Fig. 1 .
Fig.1.Basal-like breast cancer with areas of necrosis and high grade nuclei (H&Ex10)

Table 3 : Histological type, histological grade and tumour stage
11,14Some of the studied triple negative tumours may have