The present thesis analyzes, from a multi-sited perspective, the identity performances of Vitória and Glória, women in treatment of breast cancer who, through their online interactions, construct themselves as victims when they discover the disease and begin to act as protagonists in social networks in the fight against cancer. Thus, the objectives of this study are: (i) to analyze the identity performances of two women with breast cancer in different websites; and (ii) to understand how the participants construct themselves as protagonists in social networks throughout the treatment of the disease. The theoretical perspective of the research is located in studies on the identity performances in narrative and multimodal discourse, in the discursive and social protagonism and in the theory of the positioning. The methodology of the research is qualitative and interpretative of a netnographic nature. The data consist of videos, interviews and narratives of the participants that are registered in public pages of Facebook, YouTube, three institutional websites and one blog. The analysis indicate that: (i) there are changes in identity performances and in the positioning of participants in social networks, signaling the transformation of life trajectories throughout their treatments - from being ordinary to protagonism; (ii) participants reassign their experiences of pain and lamentation, from a discourse perspective as social action through discourses of emotion, hope, triumph and political engagement; (iii) agency is directed to interlocutors in social networks, as a political and identity positioning for coping with cancer. In this sense, as a social contribution, this thesis indicates that, in contemporary society, social networks become fertile spaces of resistance and personal/users empowerment, and spaces of metamorphosis from caterpillar to butterfly in relation to cancer.