Solitary breast metastases are rare and mimic primary breast carcinoma. A 60-year-old female with a history of pulmonary adenocarcinoma presented with a solitary left breast lump suspicious for malignancy on breast imaging. Core-needle biopsy disclosed an adenocarcinoma strongly and diffusely positive for oestrogen receptors. Further immunohistochemistry was consistent with the breast tumour being a solitary metastasis of her pulmonary cancer. Clinicians and pathologists should be aware of the fact that pulmonary adenocarcinomas may sometimes display strong rather than only focal positivity for oestrogen receptors by immunohistochemistry and may mimic breast cancer of no special type.