Tumour-to-tumour metastasis from papillary thyroid carcinoma with BRAF mutation to lung adenocarcinoma with EGFR mutation: the utility of mutation-specific antibodies.

AIMS: Tumour-to-tumour metastasis is a rare event. The aim of this study is to demonstrate the utility of mutation-specific antibodies to prove the occurrence of metastatic papillary thyroid cancer donor into lung adenocarcinoma recipient. METHODS AND
RESULTS: We report the case of an 80-year-old woman who had a papillary thyroid carcinoma with a v-raf murine sarcoma viral oncogene homologue B1 mutation that metastasized into a lung adenocarcinoma with an epidermal growth factor receptor mutation. Immunohistochemical analysis with mutation-specific antibodies not only clearly revealed two components, but also revealed their gene mutation statuses.
CONCLUSIONS: As a component of multimodal diagnostic tools, immunohistochemistry can avoid some pitfalls involved in the molecular diagnosis of complicated cases (such as our own) and can help to ensure that patients receive optimal treatments.