Aggressive variants of papillary thyroid cancer.

PURPOSE OF REVIEW: Aggressive variants of papillary thyroid cancer (PTC) have been recognized with increasing frequency. The most common of these include the diffuse sclerosing variant, tall cell variant, and insular thyroid cancer. These tumors may represent a spectrum of dedifferentiation from classic PTC to anaplastic thyroid cancers.

RECENT FINDINGS: Pathologists are reaching consensus in the diagnosis of these variants, recognizing their important distinction in clinical behavior. Preoperative studies such as ultrasonography, fine-needle aspiration, and better molecular and genetic markers help raise the suspicion of a thyroid nodule possibly harboring an aggressive cancer; this in turn allows the surgeons and endocrinologists to formulate a more complete operative plan, including thyroidectomy, possible lymphadenectomy, and postoperative radioactive iodine administration. In the past, most studies on these variants have relied on single institution and small clinical series; however, recent population-level analyses using national databases such as Surveillance, Epidemiology and End Result have included larger numbers of cases collected over many years.

SUMMARY: These studies have allowed for the identification of temporal trends in tumor incidence, and long-term analyses of the clinical, pathological, and survival outcomes of patients with these aggressive variants.