Fascin expression is associated with aggressive clinicopathological features in parathyroid tumors

BACKGROUND: Parathyroid tumors are classified by the World Health Organization as adenomas, atypical tumors, or carcinomas. While the loss of parafibromin expression and a Ki-67 labeling index >5% are well known markers of malignancy, the role of fascin, an actin-bundling protein implicated in cancer invasion and metastasis, has not yet been investigated in parathyroid tumors. METHODS: We examined fascin expression by immunohistochemistry in 19 carcinomas, 16 atypical tumors, 23 adenomas and 14 normal parathyroid tissues. Staining for parafibromin and Ki-67 was also performed. Fascin expression was evaluated semiquantitatively, with cases scoring ≥3 considered positive. Associations with parafibromin and Ki-67 were analyzed, and clinicopathological correlations were assessed. RESULTS: Fascin positivity was observed in 0% of normal tissues, 21.7% of adenomas, 50.0% of atypical tumors, and 42.1% of carcinomas. Nuclear fascin expression was more frequent in atypical tumors (25.0%) and carcinomas (42.1%) than in adenomas (4.3%). Parafibromin loss was detected in 43.7% of atypical tumors and 89.5% of carcinomas but not in adenomas or normal tissues. Ki-67 labeling index >5% was detected in 31.3% of atypical tumors, and 63.2% of carcinomas. Fascin-positive cases showed a higher rate of parafibromin negativity (p = 0.0071), whereas fascin expression was not correlated with Ki-67. All recurrent cases were fascin-positive, parafibromin-negative, and had a Ki-67 labeling index >5%. CONCLUSION: Although fascin immunostaining was not superior to parafibromin or Ki-67 for differential diagnosis, its higher expression in atypical tumors and carcinomas and its presence in recurrent cases indicate that fascin expression is associated with aggressive clinicopathological features.