Tumor-to-tumor metastasis: Metastatic invasive lobular carcinoma of the breast within adenocarcinoma of the lung

Tumor-to-tumor metastasis (TTM) is an extremely rare phenomenon in patients with multiple synchronous or metachronous primary malignancies. Previous studies reported that renal cell carcinoma and meningioma are the most common recipients of TTM, whereas the most prevalent donors are lung and breast carcinomas [1]. Although the lung is one of the organs most vulnerable to metastases, a lung carcinoma is one of the most rare recipients of TTM. To the best of our knowledge, only two cases of lung carcinoma harboring metastatic breast carcinoma have been reported in English literature [2]. Herein, we report another TTM case in which an invasive lobular carcinoma of the breast metastasized to a lung adenocarcinoma.