Multifocal micropapillary thyroid cancer: a new indication for total thyroidectomy?

Area of Science:

• Endocrinology
• Oncology
• Surgical Pathology

Background:

• Current American Thyroid Association guidelines recommend total thyroidectomy (TT) for thyroid cancers measuring 1 cm or greater.
• Increased use of neck sonography has led to earlier detection of papillary thyroid cancers, with many found to be multifocal or at the micropapillary level.
• Concerns exist regarding the safety of routine TT, particularly in young patients with favorable cancers, and the clinical significance of multifocal micropapillary cancers.

Purpose of the Study:

• To analyze the incidence of contralateral (bilateral) thyroid cancer in patients with well-differentiated papillary thyroid cancer (WDPTC) undergoing TT.
• To evaluate the risk factors, including tumor size, multifocality, age, and contralateral malignancy, in patients with WDPTC.

Main Methods:

• Retrospective review of 516 thyroid cancer patients.
• Analysis of a subset of 269 patients with WDPTC confined within the involved lobe undergoing TT.
• Stratification based on age, tumor size, ipsilateral multifocality, and presence of contralateral nonpalpable malignancy.

Main Results:

• Overall contralateral histologic malignancy was found in 46.4% of patients.
• The incidence of contralateral malignancy was 34% for subcentimeter tumors (<1 cm) and increased significantly to 52% for tumors 1 cm or greater (P = 0.006).
• In patients 45 years or older with subcentimeter multifocal tumors, the incidence of contralateral malignancy approached 76% (P = 0.0002).
• Permanent hypocalcemia occurred in 0.4% of patients, and there were no recurrent nerve injuries.

Conclusions:

• Bilateral thyroid cancer is significantly prevalent in patients with 1 cm or greater WDPTC.
• Patients older than 45 years with ipsilateral multifocal micropapillary cancers, even if subcentimeter, are at higher risk for bilateral disease.
• Total thyroidectomy should be considered for patients older than 45 years with ipsilateral multifocal micropapillary cancers, given its safety and the high incidence of bilateral involvement.