Sodium Iodide Symporter Expression in Adenoid Cystic Carcinoma of the Head and Neck.

Sodium iodide symporter (NIS) expression in adenoid cystic carcinoma (ACC) has not been fully elucidated in the literature, and it is unclear whether radioactive iodine may be a potential therapeutic modality. To our knowledge, the present study includes the largest ACC tumor sample size to evaluate for NIS expression. To assess whether ACC of the head and neck expresses NIS by using immunohistochemical staining techniques, as well as assess whether the presence or intensity of staining correlates with tumor or patient variables. Immunohistochemical analysis of NIS expression was performed on 20 ACC specimens from various head and neck subsites obtained from January 1, 1988, to May 6, 2013, at a single academic tertiary care medical center. Staining intensity was graded on a scale of 0 to 3+ (higher numbers indicate greater staining intensity) and was analyzed according to multiple patient and tumor variables. Tumors were eliminated from the study if the patient had undergone prior surgical resection, chemotherapy, or radiotherapy, or was receiving thyroid hormone supplementation at the time of the operation. Presence or absence of staining was the primary outcome measured; secondary outcomes were the intensity and localization of staining. Sodium iodide symporter staining was positive in 15 of the 20 tumor specimens (75%). Staining was largely localized to the cytoplasm and was of low intensity. There was no significant association between the presence or intensity of staining and the tumor subtype, tumor location, or any of the patient variables assessed (P > .05). No association between staining intensity and tumor growth pattern was shown on χ² analysis: 1+ (P = .53), 2+ (P = .14), or a combination of 1+ and 2+ staining (P = .64). Parotid control tissue demonstrated intense membranous staining of the striated parotid gland ducts. Sodium iodide symporter was expressed in the cytoplasm with low intensity in most of the tumor specimens examined in this study. These staining characteristics are also commonly found in thyroid cancer cells. Further investigation is required to determine the significance of this finding. We are optimistic that future studies using endogenous NIS stimulation and identification of genes associated with NIS plasma membrane localization could be applied to the treatment of ACC with radioactive iodine techniques.