Fascin expression is associated with aggressive clinicopathological features in parathyroid tumors

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.

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.

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%.

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.