From lung to breast: a rare case of metastatic lung adenocarcinoma presenting as a breast lump in a male patient.

Pulmonary adenocarcinoma, the most common subtype of non-small cell lung cancer, frequently metastasizes to the brain, liver, bones, and adrenal glands. However, breast metastases are exceedingly rare, accounting for 0.2%-1.3% of extramammary metastases, with only 0.1% of secondary breast malignancies originating from the lung. This case report presents a 56-year-old non-smoking male who presented with a unilateral retro-areolar breast lump. Further evaluation revealed ipsilateral axillary lymphadenopathy, and diagnostic biopsy and immunohistochemistry confirmed the lung origin of the breast lesion. This study emphasizes the significance of taking into account breast metastasis in the differential diagnosis of breast lesions in male patients, particularly those with a known primary malignancy. It highlights the need to recognize breast lumps as a potential presentation of secondary breast malignancy.