Histological patterns of locoregional recurrence in Hürthle cell carcinoma of the thyroid gland

Background: Hürthle cell carcinoma (HCC) is regarded as an aggressive variant of follicular thyroid carcinoma based in part on its propensity to metastasize regionally and recur locally. The current treatment recommendation of formal regional lymph node dissection is largely based on the presumption of lymphatic dissemination to cervical lymph nodes as the main mechanism of regional spread. The purpose of this study was to better define the distribution of locoregional recurrence in HCC, and specifically to differentiate soft-tissue implants from true nodal metastases. Methods: The surgical pathology files of The Johns Hopkins Hospital were searched for cases of HCC with locoregional recurrences. The slides were reviewed to assess the histologic patterns of tumor spread, including the presence or absence of lymph node metastasis. Elastic staining was used to confirm vessel invasion. Results: Twenty-four cases from 19 patients were identified. Thirteen were men, and the patients ranged in age from 35 to 83 years (mean 66). All had total or near-total thyroidectomies, and 16 received postoperative radioactive iodine. The time from primary diagnosis to first recurrence ranged from 0 to 12 years (mean 5 years). The locoregional disease involved the lateral neck (n=16), central neck (n=18), and larynx/trachea (n=4). In all 24 cases, the dominant tumor nodule was present as a rounded nodule of carcinoma within the soft tissues and unassociated with lymphoid tissue. Of 22 cases evaluated by elastic staining, 13 had tumor nodules within veins. True lymph node metastases were present in only six (25%) cases, and in all but one case, the lymph node metastases were <0.5cm. Conclusions: When HCC spreads in the neck, it usually does so as soft-tissue implants likely resulting from spread within venous channels. True lymph node metastases are not a major source of nodular recurrences in the neck. Resolving the pattern of tumor spread could help guide and refine the management of locoregional recurrence for patients with HCC.