Breast cancer related lymphedema (BCRL) at the arm and/or trunk is an extremely dreaded complication after breast cancer treatment due to its chronicity and impact. The incidence of objective arm and trunk/ breast BCRL is declining due to the major shift into the treatment approach of breast cancer. However, many patients report a sensation of swelling without the presence of objective BCRL, referred to as subjective BCRL. Therefore, subjective BCRL is defined as the diagnosis of BCRL based on the patient's sensation of a difference in size at the arm and/or trunk without the presence of objective BCRL. At this moment, there is no clear information on the prevalence and the transitions between different BCRL states (no-subjective-objective) over time, as well as about the underlying mechanisms and contributing factors of subjective BCRL. Therefore, the investigators hypothesize that four mechanisms might be associated with the presence and severity of subjective arm or trunk/breast BCRL, including the presence and/ or severity of lymphatic (1) and sensory processing problems (nociceptive (2), neuropathic (3), and/or central sensory processing problems (4)). The investigators will set up a prospective longitudinal study with breast cancer patients to determine the prevalence of subjective and objective arm or trunk/ breast BCRL at 1, 6, and 12 month(s) post-surgery and the transitions between different BCRL states (no-subjective-objective BCRL) (AIM 1). In addition, factors related to four potential underlying mechanisms (lymphatic, nociceptive, neuropathic, and central sensory processing problems) that contribute to the occurrence of subjective BCRL in comparison to no self-reported swelling and objective BCRL will be determined (AIM 2). Furthermore, the present study will be undertaken to determine factors related to these four underlying mechanisms that contribute to the severity of subjective BCRL at arm or trunk/ breast BCRL within the group of patients with subjective BCRL at different time-points after surgery (at 1, 6, and 12 month(s) post-surgery) (AIM 3).