Context.-Papillary thyroid carcinoma (PTC) is an uncommon tumor in the pediatric population. A limited number of studies have examined genetic mutations affecting the mitogen-activated protein kinase (MAPK) pathway in the pediatric population.Objective.-To examine mutations affecting this pathway in PTC in our pediatric population and compare the BRAF V600E mutation rates in pediatric and adult tumors.Design.-Eighty-four patients, including 14 pediatric and 70 adult, with PTC were tested for the BRAF V600E mutation by using real-time polymerase chain reaction and sequencing. Additionally, we examined the rate of RAS point mutations with real-time polymerase chain reaction and rearrangements of RET/PTC1 and RET/PTC3 in the pediatric group with fluorescence in situ hybridization. Clinical and histologic data were compared as well.Results.-Of 77 tumors that had an interpretable result, the BRAF V600E mutant was identified in 4 of 13 pediatric patients (31%) and 43 of 64 adult patients (67%), which was a significant difference (using Fisher exact test, P ¼ .03). One pediatric and 6 adult cases did not reveal an interpretable result with melting curve analysis. One of these cases harbored a rare 3-base pair deletion mutation (c.1799_1801delTGA). Mutations in RAS genes were not seen in any pediatric tumors. One tumor with a RET/PTC1 rearrangement and another with RET/PTC3 were identified in the pediatric population (15%).Conclusions.-The rate of the BRAF V600E mutation in the pediatric population is significantly lower than that seen in the adult population. Mutations in RAS do not contribute significantly to pediatric PTC. This experience from our institution adds to the growing body of knowledge regarding tumor genetics in pediatric PTC.(Arch Pathol Lab Med. 2016;140:134-139; doi: 10.5858/ arpa.2014-0612-OA) P apillary thyroid carcinoma (PTC) is an uncommon tumor in the pediatric population. Despite having an excellent prognosis with long-term mortality rates of less than 1%, 1,2 pediatric patients with PTC tend to present with advanced disease often with increased rates of extrathyroidal tumor extension, lymphovascular invasion, and distant metastases. 1,3-5The distinct clinical nature of papillary thyroid cancer in the pediatric population has prompted interest in the molecular tumorigenesis. The mitogen-activated protein kinase (MAPK) pathway includes components of particular interest, including BRAF, RAS, and RET. Between 37% and 52% of PTCs have been linked to the specific BRAF mutation V600E, and clinical correlations support that this foretells a more aggressive disease course in adults. [6][7][8][9] The incidence of this BRAF mutation in the pediatric population is thought to be lower than in adults with rates of 0% to 37%, 10-15 though 1 recent series 16 revealed a rate of 63%. The rearrangement mutations of RET are also considered a major contributor to PTC tumorigenesis, but rates of this mutation have fluctuated widely in reported series.17 RET/PTC rearrangements have been associated with young age 18 an...

The initial presentation of follicular thyroid carcinoma is rarely related to metastatic lesions. Presented here is the case of a 70-year-old woman with the initial presentation of a 13-cm chest wall mass identified as a metastatic follicular thyroid carcinoma. The chest wall lesion had features of a poorly differentiated carcinoma with areas of necrosis, an insular growth pattern focally and increased mitotic activity. A small follicular carcinoma was subsequently identified. The primary tumor was a 1-cm well-differentiated follicular carcinoma with capsular and vascular invasion. This represents a rare presentation of a follicular thyroid carcinoma with initial recognition of a large, dedifferentiated metastatic lesion from a small primary carcinoma. Dedifferentiation and metastasis in the context of microcarcinoma is an exceptionally rare event and suggests other mechanisms may be involved in disease spread other than simply increased cell proliferation.

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