Complex Differential Diagnosis between Primary Breast Cancer and Breast Metastasis from EGFR-Mutated Lung Adenocarcinoma: Case Report and Literature Review

Abstract

We present a case of a woman with epidermal growth factor receptor (EGFR)-mutated lung adenocarcinoma who received gefitinib for 2 years and obtained a partial response. The patient then developed liver metastasis and a breast lesion, displaying high estrogen receptor (ER) expression and harboring the same EGFR mutation. From the radiological studies, it was not possible to make a differential diagnosis between primary breast cancer and breast metastasis from lung cancer. After the removal of the breast nodule, thanks to the clinical history, radiology, and above all, molecular and immunohistochemical investigations, a diagnosis of breast metastasis from lung adenocarcinoma was made. This case emphasizes the importance of a comprehensive clinical, pathological, and molecular analysis in the differential diagnosis between primary breast cancer and metastases from extramammary tumor to guide adequate treatment decision making.

Metastasis of Pulmonary Carcinoma to the Breast: Case Report

“…Thyroid Transcription Factor-1 (TTF1) is a well-established biomarker for lung carcinoma and is currently one of the most widely used to find the origin of the tumor. Current data indicate that 58% of non-small cell lung carcinomas that metastasize to the breast are TTF1 positive, while in cases of primary lung adenocarcinoma the positivity is 83% 2,8 . The estrogen receptor (ER) is present in up to 80% of breast malignancies and between 7.6 to 27.2% of lung adenocarcinoma cases.…”

“…Another important element that must be highlighted in the case is the presence of the T790 mutation 2 . Epidermal growth receptor (EGFR) is a protein present in cells that plays a role associated with cell growth and survival 2,8 . It can present several mutations, one of them being the T790M mutation, which is related to resistance to EGFR tyrosine-kinase inhibitor therapy and disease progression.…”

“…Metastases from lung cancer to the breast are extremely rare 8 . The literature show that extra-mammary metastases correspond to 0.4 to 1.3% of breast carcinomas.…”

“…The literature show that extra-mammary metastases correspond to 0.4 to 1.3% of breast carcinomas. The most common tumors that metastasize to the breast are melanoma, lung cancer, renal cell carcinoma, and ovarian tumors 8,9 . Lung cancer accounts for 16 to 33% of all breast metastasis cases, with adenocarcinoma being the most common subtype 8 .…”