Multiple primary malignancies (MPM )may arise in the same organ or differentsites of the body. Wepresent a challengingcase of non-small cell lung cancer (NSCLC) with metastatic subcutaneous nodule beneath the skin of the breast, coexisting with a second lesion in the breast tissue on the same side. The latter was confirmed later as a second primary invasive breast cancer. Generally, when a patient presents with a suspicious breast mass and a firm, possibly malignant subcutaneous nodule on the same breast, this situation guides the clinician to suspect breast cancer. However, in some atypical cases, metastasis might originate from another primary cancer site, such as the lung parenchyma. Here, we report this case to improve the management of similar cases and remind clinicians to always consider such rare possibilities.