ENCAPSULATED CLASSIC AND FOLLICULAR VARIANTS OF PAPILLARY THYROID CARCINOMA: COMPARATIVE CLINICOPATHOLOGIC STUDY

Objective: To compare the clinicopathologic features of papillary thyroid carcinoma classic variant (PTC-CV) and papillary thyroid carcinoma follicular variant (PTC-FV), with a focus on the encapsulated form. Methods: In a retrospective search of computerized pathology files for 1996 to 1998, a cohort of 114 cases (58 cases of PTC-CV and 56 cases of PTC-FV) were selected for this study. Clinicopathologic data and long-term follow-up (serum thyroglobulin measurements, radiologic studies, and additional tissue sampling) through the date of compilation of study data were extracted from the medical records. Results: The median patient age at initial diagnosis was 46 years for the PTC-CV group and 45.5 years for the PTC-FV group. Complete tumor encapsulation was seen in 40 PTC-CV cases (69%) and in all PTC-FV cases (100%). A higher rate of tumor capsule invasion (CI), lymphovascular invasion (LVI), extrathyroidal extension, and lymph node metastatic lesions was seen in PTC-CV than in PTC-FV: CI, 26% versus 18%; LVI, 17% versus 4%; extrathyroidal extension, 19% versus 7%; and lymph node metastatic lesions, 68% versus 29%. Clinical, radiologic, or pathologic follow-up data were available in 36 PTC-CV cases (62%) and 34 PTC-FV cases (61%). The median duration of follow-up for the PTC-CV group was 10 years and for the PTC-FV group was 9 years. Tumor recurrence was found in 10 patients with PTC-CV (28%) and 2 with PTC-FV (6%). Distant metastatic lesions occurred in 3 patients with PTC-CV (8%) and 1 patient with PTC-FV (3%) (P = .17); of these, 2 cases of PTC-CV were encapsulated and showed CI, LVI, and lymph node metastatic lesions. Conclusion: Our current study confirms previous reports that both encapsulated PTC-CV and encapsulated PTC-FV are indolent tumors and are associated with very low mortality. (Endocr Pract. 2010;16:952-959)