Samara Skwiersky¹, Gil Hevroni¹, Gurbaj Singh¹, Lisel Hope¹, Tahmineh Haidary², Moro O. Salifu¹, Samy I. McFarlane^1,

Anaplastic thyroid cancer (ATC) is a rare, but extremely aggressive, form of cancer with a high mortality rate. Differentiated thyroid cancer (DTC), on the other hand, including papillary and follicular subtypes, are relatively common and typically follows a more indolent course. Cases have been reported in which ATC transforms from DTC, and where DTC and ATC exist simultaneously. Given the low incidence of such cases, they have not been well studied, and the optimal treatment regimen has yet to be determined. We present a case of a 77-year-old woman who was initially presented with papillary thyroid cancer (PTC) with focal ATC. Five months after undergoing total thyroidectomy, she returned with a new right sided neck mass. Fine needle aspiration (FNA) with biopsies of the mass and lymph node at one level revealed a smear pattern consistent with ATC. However, lymph node biopsy taken from a different level revealed a smear pattern consistent with PTC. Mutation analysis was performed and results were positive for metastatic BRAF V600- mutant ATC. The patient was then started on dabrafenib/trametinib chemotherapy. Seven months later, she was tolerating treatment well. These unique clinical features including the initial presentation and the relatively favorable survival, that is more than double that of the median survival rate for ATC, suggests that those with synchronous PTC and ATC may have a more indolent course with better prognosis than those with ATC alone. It is also possible that the relatively longer survival in our patient is due to the use of the BRAF inhibitor, dabrafenib and the MEK inhibitor, trametinib in this case with concurrent ATC and PTC. While patients with both PTC and ATC have been documented to have mutations in the BRAF V600 gene, the objective of this report is to present the relatively favorable outcomes when a therapeutic regimen is guided by mutation analysis. Future research into advanced treatment options including targeted therapy and /or immunotherapy for both DTC and ATC is needed. Somatic mutation testing may also be helpful to identify oncogenic kinase abnormalities that will inform therapeutic decision making.

anaplastic thyroid cancer, papillary thyroid cancer, concurrent