BACKGROUND. Poorly differentiated thyroid cancer (PDTC) and anaplastic thyroid cancer (ATC) are rare and frequently lethal tumors that so far have not been subjected to comprehensive genetic characterization. METHODS. We performed next-generation sequencing of 341 cancer genes from 117 patient-derived PDTCs and ATCs and analyzed the transcriptome of a representative subset of 37 tumors. Results were analyzed in the context of The Cancer Genome Atlas study (TCGA study) of papillary thyroid cancers (PTC). RESULTS. Compared to PDTCs, ATCs had a greater mutation burden, including a higher frequency of mutations in TP53, TERT promoter, PI3K/AKT/mTOR pathway effectors, SWI/SNF subunits, and histone methyltransferases. BRAF and RAS were the predominant drivers and dictated distinct tropism for nodal versus distant metastases in PDTC. RAS and BRAF sharply distinguished between PDTCs defined by the Turin (PDTC-Turin) versus MSKCC (PDTC-MSK) criteria, respectively. Mutations of EIF1AX, a component of the translational preinitiation complex, were markedly enriched in PDTCs and ATCs and had a striking pattern of co-occurrence with RAS mutations. While TERT promoter mutations were rare and subclonal in PTCs, they were clonal and highly prevalent in advanced cancers. Application of the TCGA-derived BRAF-RAS score (a measure of MAPK transcriptional output) revealed a preserved relationship with BRAF/RAS mutation in PDTCs, whereas ATCs were BRAF-like irrespective of driver mutation. CONCLUSIONS. These data support a model of tumorigenesis whereby PDTCs and ATCs arise from well-differentiated tumors through the accumulation of key additional genetic abnormalities, many of which have prognostic and possible therapeutic relevance. The widespread genomic disruptions in ATC compared with PDTC underscore their greater virulence and higher mortality. FUNDING. This work was supported in part by NIH grants CA50706, CA72597, P50-CA72012, P30-CA008748, and 5T32-CA160001; the Lefkovsky Family Foundation; the Society of Memorial Sloan Kettering; the Byrne fund; and Cycle for Survival.

Background: Anaplastic thyroid carcinoma (ATC) is nearly always fatal. Large studies on ATC are exceedingly rare. We aimed to study the clinical, genotypic, and histologic characteristics of ATC in the largest retrospective cohort of ATC to date. Methods: Three hundred sixty patients with ATC from two tertiary centers were studied. Molecular testing was performed in 126 cases including 107 using next-generation sequencing. Results: The median patients' age was 68 years. Differentiated thyroid carcinoma (DTC) was present in 208 cases (58%), the most common being papillary carcinoma ( n = 150). The 1-, 2-, 3-, and 5-year overall survival (OS) was 36%, 17%, 13%, and 11%, respectively. On univariate analysis, age, resectability, chemotherapy, radiotherapy, margin status, encapsulation, gross residual disease, gross extrathyroidal extension, percentage, and size of ATC in the primary tumor predicted OS ( p < 0.05). Age, resectability, chemotherapy, and gross residual disease were independent prognostic factors in the entire cohort, while gross residual disease was the only independent predictor of OS in patients who had resection of their tumor. BRAF , RAS , TERT promoter, TP53 , PIK3CA , E1F1AX , and PTEN mutations were detected in 45%, 24%, 75%, 63%, 18%, 14%, and 14% of ATC, respectively. Concomitant BRAF/RAS and TERT mutations were associated with worse outcome than mutation in only one of the genes. BRAF- mutated and RAS -mutated ATCs had similar frequency of nodal and distant metastasis. Twelve cases were pure squamous cell carcinoma, 60% of which carried BRAF ^V600E mutation and showed a similar OS to other ATCs. Conclusions: (i) Gross residual disease remains the most crucial indicator of outcome in ATC. (ii) Encapsulation, margin status, percentage, and size of ATC in the primary were prognostically relevant. (iii) Pure thyroid squamous cell carcinoma may be considered as ATC given a BRAF ^V600E genotype and similar outcome. (iv) In contrast to DTC, BRAF -mutated and RAS -mutated ATCs have similar metastatic spread. (v) Concomitant mutations of BRAF or RAS with TERT confer a worse prognosis.

Surgical resection of the primary tumor with negative margins is the gold standard for treatment of squamous cell carcinoma (SCC) of the oral tongue (SCCOT). The primary goal of an oncologic resection is the complete excision of the tumor with no residual cancer cells left behind. A microscopically positive surgical margin is associated with a higher risk for local recurrence and a poor clinical outcome.^1-3 Close margins or the appropriate margin clearance from tumor remain as a controversial debate in the literature. More importantly, the treatment of a patient with a close margin resection is often a matter of discussion among clinicians.