Metaplastic breast carcinoma is a rare subtype of breast cancer. This subtype is mostly found in association with poorly differentiated ductal breast carcinomas and rarely with other breast carcinoma types. We report the case of a 69-year-old woman with an exceptional invasive lobular breast carcinoma associated with metaplastic squamous cell bone metastasis occurring 2 years after the initial breast cancer diagnosis. Whole-exome sequencing and subsequent immunohistochemistry of the lesions were used to link the squamous cell bone metastasis of unknown origin to the primary breast carcinoma initially diagnosed. Searching for primary carcinoma when metastatic lesions of unknown origin occur can be complex. Current molecular biology techniques may help pathologists in associating metastasis with the primary carcinoma by identifying shared specific gene mutations, even when different morphological and immunohistochemical profiles are observed between the tumours.
- breast cancer
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Handling editor Cheok Soon Lee.
Contributors AB, RB and LA: designed and performed the experiments, analysed the data and wrote the manuscript. CR: assisted with the experiments. ID, FB, CC-B, SC and EM: provided patient details. AB and LA: supervised the research and designed the experiments. All authors contributed to the final version of the manuscript with their critical revision.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Next of kin consent obtained.
Ethics approval Study Ethics approval was obtained from the French Ethics Research Committee – ‘Comité de Protection des Personnes’ (CPP EST I N° 2016/03°) in Mars 2016.
Provenance and peer review Not commissioned; externally peer reviewed.