Breast cancer has a high mortality and morbidity rate. Treatment using conventional methods such as surgery, chemotherapy and radiotherapy is difficult when the carcinoma is diagnosed at an advanced stage. In order to contribute to cancer treatment, the use of Magnetohyperthermia Therapy, whose procedure consists of increasing the temperature in a region of the body affected by the neoplasm using magnetic fluids, has brought satisfactory results. In this sense, magnetic nanoparticles are part of the international multidisciplinary effort to combat breast cancer. In this work, a new sample of magnetic fluids, made up of maghemite nanoparticles coated with gold, was tested for its potential to treat breast cancer with magnetohyperthermia (MHT). Using both iron oxide and gold, a system that exploits the surface chemistry of gold while maintaining the magnetic characteristics of iron oxide.