Uterine metastasis of lung adenocarcinoma revealed by the same epidermal growth factor receptor mutation in both lung and endometrial biopsies

We experienced a rare case of uterine metastasis of non-small cell lung cancer in an 82-year-old Japanese woman revealed by detecting the same epidermal growth factor receptor (EGFR) gene mutation in both lung and endometrial biopsy specimens. The patient noticed abnormal genital bleeding at the first presentation. Further examination revealed huge masses in both lung and uterus. Biopsies from the lung and endometrium were performed. Although the pathological findings of both specimens showed similar adenocarcinomatous features including intracytoplasmic luminas, immunohistochemical analyses could not clarify whether these two tumors are lung metastasis of endometrial adenocarcinoma, uterine metastasis of lung adenocarcinoma or double primary adenocarcinomas of the lung and endometrium. Mutational analyses of EGFR gene using genomic DNA revealed that both lung and endometrial tumors had the same substitution mutation (L858R) at exon 21 which is often observed in lung adenocarcinomas. Since EGFR mutations are rarely detected in primary endometrial cancers and especially L858R mutation has not been reported in them, detection of the same L858R EGFR gene mutation in both lung and endometrial tumors strongly suggested that uterine tumor is the metastasis of lung adenocarcinoma. Mutational analyses might be useful to determine whether the tumor is primary or metastatic when the particular mutational types are observed in particular tumor types and/or particular organs.