Tumor-to-tumor metastasis in the lung: report of three cases and review of the literature

Tumor-to-tumor metastases (TTM) correspond to a rare event in which a primary tumor metastasizes to another primary tumor, whether benign or malignant. Lung carcinoma is an unusual recipient, but one of the most frequent donors. In this article, we present three cases of TTM to the lung: the first one is of a woman with a history of papillary thyroid carcinoma and ductal carcinoma in situ of the breast, with the presence of TTM and papillary thyroid carcinoma to a primary adenocarcinoma of the lung. The second case is of a woman with TTM from ductal carcinoma of the breast to a primary pulmonary adenocarcinoma, and the third is TTM from a breast ductal carcinoma to a pulmonary hamartoma. In all three cases, the clinical-pathological connection and complementary immunohistochemical studies were essential.