Clinical and molecular characteristics of secondary breast metastases from primary lung cancer: a study of 22 Chinese cases.

Background: To analyze the clinical and molecular characteristics, as well as pathologic diagnosis and treatment of lung tumors that spread to the breast in 22 Chinese patients.

Materials And Methods: A systematic literature search of PubMed, Embase, ScienceDirect, Chinese National Knowledge Infrastructure (CNKI), Chinese Science and Technology Journal Database and Wanfang Databases was conducted to identify the related studies published before March 31, 2020. A case of a 64-year-old man who underwent pneumonectomy and who was eventually diagnosed with a breast lump 5 years after surgery at our hospital, was also included in the present study. We analyzed the clinical and immunohistochemical characteristics from these case reports.

Results: The analysis totally incorporates 21 case reports and our own case, covering 22 subjects. Among all cases we found 11 adenocarcinomas, 7 small-cell carcinomas, and 4 squamous carcinomas. In addition, most of metastatic breast masses were located below or near the nipple, rather than in the outer quadrant. The results of immunohistochemistry mostly showed triple negative breast cancers.

Conclusion: A lung cancer patient with a breast tumor should suggest the possibility of metastasis. It is extremely difficult to distinguish secondary breast cancer from primary simply through medical observation and pathologic testing. Additional immunohistochemical examinations are necessary to avoid delays in diagnosis and treatment.