Breast metastasis of primary colon cancer with micrometastasis in the axillary sentinel node: a metastasis that metastasized?

A case of single breast metastasis from colon adenocarcinoma, with omolateral axillary micrometastasis, is reported with a brief review of the pertinent literature. The originality of the oncological concept of metastasis from metastasis, through lymphatics penetration, is discussed in the setting of a rare condition of breast metastasis from a colorectal carcinoma. The demonstration of axillary lymph node micrometastasis has been possible because fine needle aspiration cytology of the breast nodule was suspicious, but not conclusive for metastasis from colon cancer, so lumpectomy with sentinel node biopsy was planned. Although no disseminated nodal metastases were evident on computerized tomography scan and ultrasonography before breast surgery, the patient developed brain metastases and deteriorated rapidly; she died 16 months after presenting with the breast mass. In conclusion, solid cancers are able to further metastasize, via well-known pathways also recognized in primary cancers such as neoplastic cell invasion of peritumoral lymphatics.