Expression and significance of aquaporin-4 in thyroid carcinoma

Objective: To investigate the expression of aquaporin-4 (AQP4) in thyroid carcinoma (TC) and explore its clinical significance.

Materials and methods: The formalin-fixed paraffin-embedded specimens including 275 TC cancer tissues, 258 corresponding paracancerous thyroid tissues and their clinicopathologic data were retrospectively analyzed. Immunohistochemical EnVision two-step method was used to detect the expression of AQP4 in the cancer tissues and adjacent thyroid tissues, and its clinical significance was analyzed.

Results: AQP4 could be expressed in both TC cancer tissues and paracancerous thyroid tissues. In TC cancer tissues, the positive expression rate was 99.3% (273/275), and the positive expression rate was 86.4% (223/258) in paracancerous thyroid tissues. The expression level of AQP4 in cancer tissues was significantly higher than that in paracancerous thyroid tissues, and the difference was statistically significant (P < 0.05). The positive expression rates of AQP4 in papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC), medullary thyroid carcinoma (MTC) and undifferentiated thyroid carcinoma (UTC) were 99.2% (258/260), 100.0% (6/6), 100.0% (6/6) and 100.0% (3/3), respectively and there was little difference in different types of TC. Analysis of relationship between expression level of AQP4 in 275 TC cancer tissues and 260 PTC cancer tissues and clinicopathologic characteristics of patients was not significant correlation (P > 0.05). Among the 275 patients, one (0.4%, 1/275) was diagnosed as neuromyelitis optica spectrum disorder (NMOSD) associated with TC.

Conclusions: AQP4 is generally expressed in TC cancer tissues and paracancerous thyroid tissues. Expression level of AQP4 in cancer tissues was significantly higher than that in paracancerous thyroid tissue. Expression level of AQP4 in TC cancer tissues is not related to the clinicopathological characteristics of the patients. Paraneoplastic NMOSD caused by TC is rare, and whether its specific pathogenesis is related to the expression of AQP4 in TC still needs further study.