The spread of instant messenger systems provides an excellent opportunity and a helpful tool to healthcare professionals. WhatsApp instant messenger use is widely prevalent among health professionals, cancer patients, caregivers and the general population. It is a quick and easy communication tool that may also be used on personal computers and business purposes. WhatsApp instant messenger and other similar tools may be a very useful complement for e-medicine. Instant messaging systems may be helpful, especially in rural areas, in medium- or low-income countries, or to avoid unnecessary travels, improve knowledge and awareness of cancer, monitor home care and support the delivery of home care. The unregulated use of WhatsApp instant messenger requires sound and shared guidelines to assure impeccable professional service. Although a significant number of papers have investigated the roles of social networks in connecting patients to health professionals, there is still a lack of information and scientific data about their uses, benefits and limitations in connecting health providers only for professional communication. The role of instant messenger systems in cancer practice and research needs to be clarified. In this paper, we report a focus on available data, pros and contras of the unregulated use of WhatsApp instant messaging, in the context of e-medicine, as an interprofessional and doctor/patient communication tool in oncology.