Abstract: A method of assessing recurrence status in a breast cancer patient comprises a step of assaying a biological sample from the patient for a level of a biomarker selected from S100? or HOX-C1I, wherein positive detection of one or both of the biomarkers is indicative of a positive recurrence status. Suitably, the method is a method of prognosis of poor disease free survival in a breast cancer patient, wherein positive detection of one or both of the biomarkers is indicative of poor disease survival. The method may also be a method of diagnosis of recurrence, wherein positive detection of circulating S100? is a diagnostic variable of recurrence. The method of diagnosis is carried out on a patient who is undergoing first line therapy and/or a patient who has had surgery to remove a primary breast tumour.