Can we rely on pathologic parameters to define conservative treatment of papillary thyroid carcinoma?

Papillary thyroid carcinoma is the most common malignant tumor of the thyroid and usually behaves in an indolent fashion. At most institutions these tumors are treated by near-total or total thyroidectomy followed by radioactive iodine ablation. The 2 main reasons for this extensive treatment include high rate of multicentricity in papillary carcinoma and difficulty in ablating large thyroid remnants with radioactive iodine after partial thyroidectomy. Some authors believe, however, that this treatment protocol may not be justified in all cases of papillary carcinoma. We analyzed 253 total thyroidectomies performed for papillary thyroid carcinoma for the following pathologic variables: tumor size, presence of tumor capsular and/or vascular invasion, intrathyroidal spread, tumor in the contralateral lobe, and lymph node metastases. Tumors measuring less than 1 cm and those with extrathyroidal soft tissue extension were excluded from this study. Among 253 cases (197 females, 56 males, age range 14-88 years), the primary tumor size ranged from 1-9.5 cm; 162 cases were completely encapsulated. Tumor capsule invasion was seen in 139 (86%) and vascular invasion was present in 32 (13%) cases; of these 27 (11% of the total) patients showed both tumor capsule and vascular invasion. Seventy-four (29%) patients showed tumor in the contralateral lobe; in 35 (47%) of these cases the contralateral tumor measured less than 1.0 cm. Lymph nodes were sampled in 106 cases, metastases were present in 67 (67/106 = 63%) and only 16 cases with lymph node metastases showed contralateral tumors. No significant correlation was noted between tumor size, occurrence of contralateral tumors, and lymph node metastases. Seventy-one percent of cases included in this study failed to show contralateral tumors. Hence, pathologic parameters such as lack of vascular invasion and lack of multifocality may be used to identify patients who can benefit from conservative therapy alone.