Metastasis of lung adenocarcinoma to the breast in core needle biopsy:clinicopathological features and gene mutations analysis

CUI Lifang; CHEN Huang; LEI Ting; ZHANG Shuang; JIANG Xi; ZHONG Dingrong

doi:10.3969/j.issn.1007-8096.2026.01.001

Abstract：Objective To investigate the clinicopathologic features and gene mutations of metastatic lung adenocarcinoma to the breast,in order to distinguish metastatic lesions from primary breast cancer.Methods A total of 5 cases were collected.The morphological and immunohistochemical characteristics of tumors in breast tissue were observed,and molecular detection of lung adenocarcinoma was performed by PCR.Results All patients were female,with age ranging from 47 to 60 years(median 50 years).The time from the diagnosis of primary lung cancer to the current breast metastasis was 0 to 64 months.PET/CT showed that breast metastasis was found along with metastases to other sites in 4 patients,including bone,lymph nodes,and subcutaneous tissues.Histologically,the tumor infiltrated surrounding normal breast tissue.None of the cases showed an in situ ductal carcinoma and none showed micro-calcifications.Lymphatic vessel emboli were observed in 1 case,necrosis was found in 2 cases.Immunohistochemically,TTF-1 was positive in all cases,NapsinA was positive in 4 cases,ER was weakly positive in 2 case,HER2(1+)was observed in 2 cases;GATA3 and PR were negative in all cases.Primary lung adenocarcinoma showed different genetic mutations by PCR,including HER2-Exon 20 ins,K-RAS Exon 2,EGFR-Exon 21(L858R),EGFR-Exon 18(E709A,G719A)mutation.3 patients died after breast metastasis,1 was alive and 1 was lost of follow-up.Conclusion Differential diagnosis between primary breast cancer and metastatic lung adenocarcinoma is difficult.Microscopic,immunohistochemical and radiologic findings in conjunction with the patient's clinical history should be considered in order to provide accurate diagnosis and treatment for patients.