To understand pain pathophysiology in terms of risk factors and protective mechanisms ranging from molecular pathways to societal impacts.

Pain and loss of function are intimately associated with the reaction of the nervous system to neural damage. A lesion to the somatosensory nervous system caused by mechanical trauma, metabolic disease, neurotoxic chemicals, infection or tumor invasion may give rise to neuropathic pain. Neuropathic pain affects around 8% of the population and may negatively impact the individual's quality of life; moreover, the condition leads to significant costs to the healthcare system and society. Not all subjects with such a lesion develop neuropathic pain, and those who do develop neuropathic pain have varying degrees of symptom severity, impact and outcomes and may respond unpredictably to treatment.

The interaction between genetics and environmental and clinical factors in a susceptible individual most likely contribute to the variation in pain prevalence and severity. A better understanding of the exact nature of these risk factors and their interactions will ultimately improve the patients' health, both in terms of recognizing patients at risk and identifying new treatment modalities.

Genetic, neurophysiological and psychological factors all influence the risk of developing persistent pain. It is therefore possible to describe a genetic, neurophysiological and psychological profile, in particular in patients experiencing neuropathic pain after surgery and/or neurotoxic chemotherapy.

Inclusion Criteria:

• Patients scheduled for breast cancer resection performed via lumpectomy (partial or segmental mastectomy) or mastectomy with or without sentinel lymph node biopsy and axillary lymph node dissection, and any combinations hereof.
• Willingness and ability to comply with study procedures as judged by the site investigator/manager.
• Expected availability for follow-up throughout the study, i.e., ~12 months.
• Willingness to voluntarily sign and date the study-specific informed consent form.

Exclusion Criteria:

• Mental incapacity or language barriers precluding adequate understanding of study procedures.
• Current alcohol or substance abuse according to the site investigator's medical judgement.
• Unsuitability for participation in the study for any other reason, e.g. due to a significant serious underlying condition (e.g. other cancer or AIDS), as determined by the site investigator/manager.

Patients scheduled for breast cancer resection at the Department of Breast Surgery, Aarhus University Hospital, Aarhus, and the Breast Surgery Clinic, Viborg Regional Hospital, Viborg, Denmark.