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

AimsTumour-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 resultsWe 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 lungadenocarcinoma 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. ConclusionsAs 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 helptoensure that patients receive optimal treatments.