Secondary breast cancer: a 5-year population-based study with review of the literature.

Secondary tumours in the breast are rare. Based on literature, an incidence of 0.4-2% is reported. In this population-based study, secondary breast tumours from a 5-year period (2001-2005), not including metastasis from contralateral breast carcinoma, were reviewed (Vestfold County, Norway). A total of 722 patients with breast malignancies were found in this population (89.3% from Vestfold County Hospital). Ten of these, approximately 1.4%, were metastatic tumours, representing four cutaneous melanomas, three pulmonary carcinomas and three malignant lymphomas. The tumours were often solitary, palpable and close to the skin. Radiologically, the lesions mostly resembled primary carcinomas by mammography and ultrasound, which differs from other studies. Comparison with a known primary tumour and use of immunohistochemical profiling is of crucial importance. Melanoma markers (Melan-A, HMB-45, S-100 protein), lung cancer markers (Cytokeratins, TTF1, Chromogranin, Synapthophysin) and lymphoid markers (CD3, CD20) usually help to confirm a secondary breast tumour diagnosis. This approach is especially indicated in diffusely growing tumours with lack of glandular structure and high-grade cytological features, and staining for ER and GCDFP15 may be helpful. Thus, the diagnosis of a breast metastasis may be suspected by careful mammography and ultrasound imaging, although some cases have atypical radiological features, and histological examination might be necessary to ensure a correct diagnosis and appropriate treatment.