Intrathyroidal tumors presenting with extranodal extension: what are we missing?

Area of Science:

• Oncology
• Pathology
• Surgical Oncology

Background:

• Extranodal extension (ENE) is a poor prognostic indicator in well-differentiated thyroid cancer (WDTC).
• Extrathyroidal extension (ETE) predicts ENE in WDTC with positive lymph nodes, suggesting tumor biology concordance.
• The predictive value of primary tumor histology for ENE in intrathyroidal WDTC remains unclear.

Purpose of the Study:

• To investigate whether specific histologic features of primary intrathyroidal WDTC tumors predict lymph node ENE.
• To identify potential markers of aggressive tumor biology in early-stage WDTC.

Main Methods:

• Retrospective review of 39 patients with WDTC and positive lymph nodes (Jan 2004-Mar 2013).
• Compared histologic features (tumor size, capsule, infiltration, sclerosis, lymphocytic thyroiditis, psammoma bodies, LVI, PNI, architecture, focality) between ETE-negative/ENE-positive (n=12) and ETE-negative/ENE-negative (n=27) intrathyroidal tumors.
• Statistical analysis using Mann-Whitney and Fischer exact tests.

Main Results:

• No statistically significant differences were found in tumor size or the nine other examined histologic features between the ENE-positive and ENE-negative groups.
• Features like tumor size (p=0.072), encapsulation, infiltration, sclerosis, lymphocytic thyroiditis, psammoma bodies, lymphovascular invasion, perineural invasion, architecture, and focality did not significantly predict ENE.
• None of the evaluated histologic features reliably predicted extranodal extension in intrathyroidal WDTC.

Conclusions:

• Histologic examination of primary intrathyroidal WDTC tumors does not currently identify those with a higher risk of extranodal extension.
• Molecular analysis of intrathyroidal tumors is necessary to uncover features that predict ENE and aggressive behavior.
• Further research is needed to understand the molecular underpinnings of aggressive WDTC phenotypes.