Background Fine needle aspiration biopsies (FNAB) of the thyroid categorized as atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is a newly defined category per the recent Bethesda guidelines. In this study, we sought to assess the characteristics and treatment of patients with an AUS/FLUS FNAB at our institution. Additionally, we evaluated the utility of the recommended three-month timing of repeat FNAB. Methods A retrospective study of all patients with an FNAB categorized as AUS/FLUS between 1/2005–12/2007 at an academic, tertiary care center. Clinical, cytological and ultrasound variables were compared among management groups. Differences in patients receiving repeat FNAB before or after a three-month interval were also compared. Results 203 patients of the 5,391 FNAB’s performed at our institution met the Bethesda criteria for AUS/FLUS. 62% were triaged directly to surgery (group I), 25% had a repeat FNAB (group II) and 13% were observed (group III). Younger (p = 0.006), male patients (p = 0.04) were more likely to go directly to surgery. 2.4% of males were observed vs. 16% of the women (p = 0.04); Timing of repeat FNAB (< or ≥ 3 months) did not alter the results of the second FNAB (p = 0.73). The overall rate of malignancy in patients undergoing surgery was 15.7%. Conclusion(s) Current practice relies mainly on established prognostic factors such as gender, and age. Timing of repeat biopsy did not alter management, repeat FNAB diagnosis, or rate of malignancy in our cohort.

Purpose B-RafV600E may play a role in the progression from papillary thyroid cancer to anaplastic thyroid cancer (ATC). We tested the effects of a highly selective B-RafV600E inhibitor, PLX4720, on proliferation, migration, and invasion both in human thyroid cancer cell lines (8505cB-RafV600E and TPC-1RET/PTC-1 and wild-type B-Raf) and in primary human normal thyroid (NT) follicular cells engineered with or without B-RafV600E. Experimental Design Large-scale genotyping analysis by mass spectrometry was performed in order to analyze >900 gene mutations. Cell proliferation and migration/invasion were performed upon PLX4720 treatment in 8505c, TPC-1, and NT cells. Orthotopic implantation of either 8505c or TPC-1 cells into the thyroid of severe combined immunodeficient mice was performed. Gene validations were performed by quantitative polymerase chain reaction and immunohistochemistry. Results We found that PLX4720 reduced in vitro cell proliferation and migration and invasion of 8505c cells, causing early downregulation of genes involved in tumor progression. PLX4720-treated NT cells overexpressing B-RafV600E (heterozygous wild-type B-Raf/B-RafV600E) showed significantly lower cell proliferation, migration, and invasion. PLX4720 treatment did not block cell invasion in TPC-1 cells with wild-type B-Raf, which showed very low and delayed in vivo tumor growth. In vivo, PLX4720 treatment of 8505c orthotopic thyroid tumors inhibited tumor aggressiveness and significantly upregulated the thyroid differentiation markers thyroid transcription factor 1 and paired box gene 8. Conclusions Here, we have shown that PLX4720 preferentially inhibits migration and invasion of B-RafV600E thyroid cancer cells and tumor aggressiveness. Normal thyroid cells were generated to be heterozygous for wild-type B-Raf/B-RafV600E, mimicking the condition found in most human thyroid cancers. PLX4720 was effective in reducing cell proliferation, migration, and invasion in this heterozygous model. PLX4720 therapy should be tested and considered for a phase I study for the treatment of patients with B-RafV600E ATC.

Human anaplastic thyroid cancer (ATC) is a lethal disease with an advanced clinical presentation and median survival of 3 months. The BRAF(V600E) oncoprotein is a potent transforming factor that causes human thyroid cancer cell progression in vitro and in vivo; therefore, we sought to target this oncoprotein in a late intervention model of ATC in vivo. We used the human ATC cell line 8505c, which harbors the BRAF(V600E) and TP53(R248G) mutations. Immunocompromised mice were randomized to receive the selective anti-BRAF(V600E) inhibitor, PLX4720, or vehicle by oral gavage 28 d after tumor implantation, 1 wk before all animals typically die due to widespread metastatic lung disease and neck compressive symptoms in this model. Mice were euthanized weekly to evaluate tumor volume and metastases. Control mice showed progressive tumor growth and lung metastases by 35 d after tumor implantation. At that time, all control mice had large tumors, were cachectic, and were euthanized due to their tumor-related weight loss. PLX4720-treated mice, however, showed a significant decrease in tumor volume and lung metastases in addition to a reversal of tumor-related weight loss. Mouse survival was extended to 49 d in PLX4720-treated animals. PLX4720 treatment inhibited cell cycle progression from 28 d to 49 d in vivo. PLX4720 induces striking tumor regression and reversal of cachexia in an in vivo model of advanced thyroid cancer that harbors the BRAF(V600E) mutation.