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

Extranodal extension (ENE) is an indicator of poor prognosis in well-differentiated thyroid cancer (WDTC). We have demonstrated that extrathyroidal extension (ETE) predicts ENE in patients with positive lymph nodes, indicating concordance between primary tumor and lymph node biology. In an effort to determine if there were other histologic features of the primary tumors that indicated an aggressive biology, we examined a subset of patients with intrathyroidal (T1/T2) disease whose lymph nodes had ENE. A review was conducted from January 2004 to March 2013. The histologic features of ETE-negative/ENE-positive tumors (group A, 12 cases) were compared with a random sample of ETE-negative/ENE-negative node-positive patients (group B, 27 cases). Cases were reviewed for size, capsule presence, infiltration, sclerosis, lymphocytic thyroiditis (LT), psammoma bodies, lymphovascular invasion (LVI), perineural invasion (PNI), architecture/cytomorphology, and focality. Size was compared using the Mann-Whitney test, while the remaining features were compared using a Fischer exact test. The breakdown of pathologic features of groups A/B were as follows: 2.28 cm/1.46 cm mean tumor size, 90 %/67 % unencapsulated, 100 %/89 % infiltrative, 100 %/89 % sclerotic, 60 %/52 % LT, 30 %/59 % positive psammoma bodies, 0 %/11 % LVI, 0 %/4 % PNI, 90 %/96 % classic architecture, 50 %/44 % multifocal. Neither size (p = 0.072) nor the other nine histologic features examined reached statistical significance. None of the histologic features appeared to significantly predict ENE. Further examination of intrathyroidal tumors at a molecular level is necessary to determine if there are any identifiable features of intrathyroidal tumors that predict ENE and thus a more aggressive phenotype.