Dendritic cells (DCs) are antigen-presenting cells and mature from precursor CD34+ stromal cells (dendritic interstitial cells [DICs]) or monocytes. The aim of the present study was to gain insight into the local immune response to various thyroid lesions. We investigated, immunohistochemically, the presence of S-100+ DCs and CD34+ DICs in 13 papillary carcinomas, 10 follicular carcinomas, 7 follicular adenomas, 1 Hurthle cell carcinoma, 1 Hurthle cell adenoma, 2 medullary carcinomas, 6 undifferentiated carcinomas, and 3 nodular goiters. Dense infiltrates of S-100+ DCs were noted in the majority of papillary carcinomas (mean: 66.4), while moderate infiltrates were observed in follicular adenomas (mean: 23.3), follicular carcinomas (mean: 23.5), and undifferentiated carcinomas (mean: 31.6). The remaining lesions showed slight infiltrates of scattered DCs. DICs were noted exclusively in neoplastic lesions, specifically at the periphery and within the tumor capsule. The increased number of DCs in papillary carcinomas is possibly correlated with their good prognosis. The specific distribution of DICs suggests a possible contribution to growth regulation of thyroid neoplasms.