[Atypical metastatic breast localization in lung cancer]. / Localisation secondaire atypique au « sein ¼ des cancers bronchiques.

INTRODUCTION: In the context of bronchial cancers, the most frequent sites for metastases to occur are the lung, bone, brain, liver and adrenal glands. However, metastasis to other sites does additionally occur and this might be influenced by the biological characteristics of the tumour. OBSERVATION: We report the case of a 54-year-old woman with a primary bronchial adenocarcinoma with an EML4-ALK translocation. During her treatment with crizotinib, the patient developed a lesion in her right breast. The initial pathological diagnosis was of an invasive ductal adenocarcinoma of the breast. However, an additional immuno-histochemical analysis revealed it to be a metastasis from her bronchial tumour. CONCLUSION: This case is an illustration that, in the context of a lung cancer with ALK rearrangement, synchronous or secondary lesions must be interpreted with caution. Specific biological analysis - ALK immunohistochemistry or FISH - must be performed to confirm a primary or metastatic origin for these lesions.