Tumor deposits in thyroid carcinomas

Tumor deposits (TDs) are defined as discontinuous neoplastic masses within the lymphatic drainage pathway of the primary tumor. The poor prognostic implication of these masses have been demonstrated in various cancers. The aim of this study is to investigate the incidence of TDs in our thyroid carcinoma cases, which has not been studied so far to the best of our knowledge, and to determine the prognostic value of their existence. In this retrospective cohort study, 194 thyroid carcinoma cases with cervical lymph node sampling and/or dissection were reevaluated for TDs. The case series consisted of 176 thyroid papillary carcinoma (TPC) and 18 thyroid medullary carcinoma (TMC) patients. TDs were detected in 54 (27.8%) patients. TMC cases (55.6%) had significantly more TDs compared to TPCs (25.0%; P = .006). TDs were more common in women (P = .045), and in multifocal tumors (P = .017). In addition, cases with TDs had larger tumor size (P = .002), more lymphatic invasion (P = .009), extrathyroidal extension (P < .001), and distant metastasis (P < .001). The mean follow-up period of the patients was 120.1 months (range, 4-341 months). Locoregional recurrence detected in 17 patients (8.8%) was more common in TMC (33.3%) than TPC cases (6.3%; P = .002). Distant metastasis was identified in 27 patients (13.9%). Ten-year recurrence free survival (RFS) and overall survival (OS) for all patients were 89.0% and 92.4%, respectively. Mean estimated OS time for TD negative and TD positive cases were: 281.9 (±17.2), 325.6 (±6.2) and 217.6 (±27.4) months, respectively (P = .002). Sex (P = .001), tumor type (P = .002), pT classification of the tumor (P < .001), perineural invasion (P = .002) and TDs (P = .002) were significantly associated with OS. In TPC cases individually, extrathyroidal extension (P = .001) and TDs (P = .002) were significantly correlated with distant metastasis. In multivariate analysis, only tumor size was detected as an independent prognostic marker in TPC cases (P = .005). Our results demonstrate the existence of TDs in thyroid carcinoma cases, and indicate a more aggressive behavior pattern of TDs in these tumors.