Unusual metastases from differentiated thyroid cancers: A multicenter study in Korea

Area of Science:

• Oncology
• Endocrinology
• Pathology

Background:

• Distant metastasis from differentiated thyroid cancer (DTC) is a primary cause of mortality.
• Unusual metastatic sites in DTC are rare and poorly understood.
• This study focuses on the clinical and pathological aspects of rare DTC metastases.

Purpose of the Study:

• To evaluate the clinico-pathological findings of unusual metastases in DTC patients in Korea.
• To analyze treatment outcomes for patients with rare DTC metastases.
• To improve understanding of the clinical course of uncommon DTC metastatic sites.

Main Methods:

• Retrospective review of medical records from four Korean tertiary hospitals.
• Diagnosis of unusual metastases confirmed by cytology/histology and/or imaging (FDG-PET/CT, I-131 WBS) with elevated thyroglobulin.
• Analysis of primary tumor pathology, metastatic site diagnosis, and treatment response.

Main Results:

• 19 patients had 25 unusual metastatic foci, predominantly papillary thyroid carcinoma.
• The median time to metastasis was 110 months; 21.1% had synchronous metastases.
• Unusual sites included solid organs (kidney, liver, pancreas, adrenal, ovary) and skin/muscles; 68.8% were radioiodine-refractory.
• Tyrosine kinase inhibitors (e.g., lenvatinib) showed efficacy in some patients.

Conclusions:

• Unusual DTC metastases are likely underestimated due to rarity and metachronous presentation.
• Clinical outcomes of unusual metastases may not differ significantly from common distant metastases.
• Further research is needed to fully understand the behavior and management of rare DTC metastases.