Systematic review of lung cancer with breast metastasis.

Background: Lung cancer with metastatic spread to the breast is a rare entity that is not commonly considered on the differential of diagnoses in the clinical context of new breast masses. The aim of our study is to provide a comprehensive literature review to highlight key clinical and histological features. Methods: A comprehensive review of literature from 1962 to 2024 regarding lung cancer with breast metastasis using PubMed was performed alongside an exemplary patient description. Data collection consisted of variables categorized as patient demographics, clinical disease characteristics, tumor immunohistochemistry and biomarker profile, and disease management and clinical outcomes. Results: Eighty-three studies consisting of case reports and case series were used for data collection and analysis, which consisted of 145 unique patient profiles. Of the included patients, 65.5% had adenocarcinoma, which was consistent with the reported chemical staining and molecular profiles; 49.6% had metachronous metastatic and primary disease with an average time to breast diagnosis of 24.2 months; 66.2% presented with an additional site of metastatic disease; 24.5% were initially misdiagnosed as having primary breast cancer. The overall mortality was 62.5% of those with reported survival outcomes, with an average follow-up of 15.0 months. Conclusions: Patients with lung cancer who have metastasized to the breast are at elevated risk for being misdiagnosed with primary breast cancer and may receive unnecessary surgery and incorrect treatment regimens.