IGF-1R Expression has More Potential Proliferation Effect in Invasive Breast Carcinoma Of No Special Type Compared to HER-2 Expression Yessy Setiawati 1 , Aswiyanti Asri 1 , Rosfita Rasyid 2 yessyamri@gmail.com 1 , aswiyanti.asri@gmail.com 1 , rosfitarasyid135ros@gmail.com 2 Department of Pathology Anatomic of Andalas University, Padang, Indonesia 1 Department of Public Health of Andalas University, Padang, Indonesia 2 Abstract. About 75% of breast carcinoma is invasive carcinoma of no special type (NST) and between 20%-30% of breast carcinoma is HER-2 positive. HER-2 overexpression now is a predictive factor for targeted therapy with anti-HER-2 agent like trastuzumab (herceptin). However, primary (de novo) resistance with trastuzumab occured in 65% patients and secondary resistance occured in 70% patients who have had good initial response. IGF-1R expression have been reported high in many malignancies including breast carcinoma. Researches have showed that IGF-1R signaling pathway have a cross- talk with HER-2 signaling pathway and was thought to become one of resistance mechanism in anti-HER-2 targeted therapy. This research was a retrospective observational cross-sectional study with a total 55 samples. Expression of IGF-1R and HER-2 was evaluated immunohistochemically. A strong positive IGF-1R cytoplasm and membranous expression was found in 18,2% and 34,5% cases, respectively. HER-2 expression was positive in 23,6% cases. IGF-1R cytoplasm expression was correlated significantly with mitosis count (p=0.049). There was no correlation between IGF-1R membranous expression with mitosis count (p=0,641). There was no correlation between IGF-1R membranous and cytoplasm expression with histological grade (p=1,000) and there was no correlation between HER-2 expression with mitosis count (p=0,495) and histological grade (p=1,000). IGF-1R expression has more potential effect in mitosis compared with HER-2 expression. Inhibition it’s signaling pathway may have therapeutic value in breast carcinoma. Combination therapy of anti-HER-2 with anti-IGF-1R could overcome resistancy of trastuzumab in HER-2 positive breast carcinoma. Keywords : Invasive breast carcinoma of NST, IGF-1R and HER-2 expression. 1 Introduction Approximately 75% breast carcinoma is invasive carcinoma of no special type (NST) (1). Breast carcinoma is heterogenous disease. Tumor with similar histologic subtype can have different clinical outcome and response to systemic therapy (2). Invasive carcinoma of NST have been reported to show highest heterogeneity among other subtype of breast carcinoma (3). Breast carcinoma is the most common malignancy in woman all over the world (4). According to data from GLOBOCAN 2012, new cases of breast carcinoma was approximately 1,67 million (43 cases per 100,000 people) (5). A total of 48,998 breast carcinoma cases (40,3 ICOMHER 2018, November 13-14, Padang, West Sumatera, Indonesia Copyright © 2019 EAI DOI 10.4108/eai.13-11-2018.2283795