Whole Tumor Capsule Is Prognostic of Very Good Outcome in the Classical Variant of Papillary Thyroid Cancer
Carlotta Giani, Liborio Torregrossa, Teresa Ramone, Cristina Romei, Antonio Matrone, Eleonora Molinaro, Laura Agate, Gabriele Materazzi, Paolo Piaggi, Clara Ugolini, Fulvio Basolo, Raffaele Ciampi, Rossella Elisei
Abstract
CONTEXT: Tumor capsule integrity is becoming a relevant issue to predict the biological behavior of human tumors, including thyroid cancer. OBJECTIVE: This work aims to verify whether a whole tumor capsule in the classical variant of papillary thyroid carcinoma (CVPTC) could have as a predictive role of a good outcome as for follicular variant (FVPTC). METHODS: FVPTC (n = 600) and CVPTC (n = 554) cases were analyzed. We distinguished between encapsulated-FVPTC (E-FVPTC) and encapsulated-CVPTC (E-CVPTC) and, thereafter, invasive (Ei-FVPTC and Ei-CVPTC) and noninvasive (En-FVPTC and En-CVPTC) tumors, according to the invasion or integrity of the tumor capsule, respectively. Cases without a tumor capsule were indicated as invasive-FVPTC (I-FVPTC) and invasive-CVPTC (I-CVPTC). The subgroup of each variant was evaluated for BRAF mutations. RESULTS: E-FVPTC was more frequent than E-CVPTC (P < .001). No differences were found between En-FVPTC and En-CVPTC or between Ei-FVPTC and Ei-CVPTC. After 18 years of follow-up, a greater number of not-cured cases were observed in Ei-CVPTC with respect to Ei-FVPTC, but not in En-CVPTC to En-FVPTC. Multivariate clustering analysis showed that En-FVPTC, En-CVPTC, and Ei-FVPTC have similar features but different from I-FVPTC and I-CVPTC and, to a lesser extent, from Ei-CVPTC. A total of 177 of 614 (28.8%) cases were BRAFV600E mutated, and 10 of 614 (1.6%) carried BRAF-rare alterations. A significantly higher rate of En-CVPTC (22/49, 44.9%) than En-FVPTC (15/195, 7.7%) (P < .0001) were BRAFV600E mutated. CONCLUSION: En-CVPTC is less prevalent than En-FVPTC. However, it has good clinical/ pathological behavior comparable to En-FVPTC. This finding confirms the good prognostic role of a whole tumor capsule in CVPTC as well. New nomenclature for En-CVPTC, similar to that introduced for En-FVPTC (ie, noninvasive follicular thyroid neoplasm with papillary-like nuclear features; NIFTP) could be envisaged.