The potential diagnostic value of Rac1 immunohistochemistry in follicular thyroid carcinoma

Rac1 and Galectin-3 has been suggested to involve in the invasion and aggressive behaviour of several cancers. The aim of this study is to evaluate the immunoreactivity of Rac1 and Galectin-3 in follicular adenoma (FA) and follicular thyroid carcinoma (FC) in an attempt to investigate its association with the invasion of FC and its immunohistochemical diagnostic value to discriminate FA and FC.

This study included 120 selected paraffin embedded tissue blocks from surgically resected follicular thyroid neoplasms, consists of 60 cases of FA and 60 cases of FC. Immunohistochemistry staining for Rac1 and Galectin-3 were performed on all cases. The diagnostic value of these immunohistochemical markers to determine invasion in FC were calculated.

Positive immunoreactivity of Rac1 were found in 25/60 (41.67%) cases of FA and 56/60 (93.3%) cases of FC (p=0.0001). Positive immunoreactivity of Galectin-3 was found in 8/60 (13.3%) cases of FA and 47/60 (78.3%) cases of FC (p=0.0001). The sensitivity of Rac1 in distinguishing FA from FC were 93.3% with specificity, PPV, NPV, and overall accuracy were 58.3%, 69.1%, 89.7%, and 75.8% consecutively. The sensitivity of combination Rac1 and Galectin-3 were 73.3% with specificity, PPV, NPV, and overall accuracy were 96.7%, 95.7%, 78.4%, and 85% consecutively.

Rac1 immunohistochemistry is a sensitive marker in discriminating FA from FC, but its specificity and accuracy are low. Combination of Rac1 and Galectin-3 gives more specific and higher diagnostic accuracy. Combination of Rac1 and Galectin-3 may be useful to determine invasion and diagnose FC.