Metastatic Follicular Thyroid Carcinoma and the Primary Thyroid Gross Examination: Institutional Review of Cases from 1990 to 2015

The diagnosis of follicular-patterned carcinomas, including follicular thyroid carcinoma, oncocytic (Hürthle cell) carcinoma, and the encapsulated follicular variant of papillary thyroid carcinoma, requires evidence of capsular and/or vascular invasion. With minimally invasive carcinomas classified often within less than a millimeter of tissue segregating them from adenomas and non-invasive follicular thyroid neoplasms with papillary-like nuclear features, opinions vary internationally over how much of the capsule to submit in order to deem it well enough represented, considering that even if grossly entirely submitted in microcassettes, without leveling through each tissue block, the capsule is truly never entirely examined microscopically. Here, we retrospectively examine submission practices and outcomes at a single, high-volume institution over a 25-year period. Our results indicate that the vast majority of lesions with poor outcomes are those with wide invasion, and tumors lacking gross evidence of capsular perturbation rarely lead to recurrence or metastasis, an unsurprising result that should prompt re-evaluation of our grossing methods and approach to follicular-patterned tumors in a time of cost restraint, molecular diagnostics, and low biological potential of encapsulated, circumscribed neoplasia of the thyroid.