Bilateral follicular variant of papillary thyroid cancer with different RAS mutations detected with next-generation sequencing: Report of an unusual case and literature review.

Multifocality in papillary thyroid carcinoma (PTC) is a common finding, but the clonal relationship between individual tumors remains uncertain. While multiple synchronous tumor foci of PTC may develop through permeation of intraglandular lymph vessels of a single malignant clone, they can also arise from independent progenitor clones sustained by different genetic events. We report the case of a 37-year-old man who underwent total thyroidectomy after fine-needle aspiration of two bilateral thyroid nodules that yielded cytological findings consistent with atypia of undetermined significance/follicular lesion of undetermined significance.