NPM1 and undifferentiated carcinoma: Pianta et al. analyzed nucleophosmin expression in thyroid tumors and found differences in nucleophosmin expression between benign (follicular adenomas) and malignant tumors (papillary carcinoma, follicular carcinoma and undifferentiaded carcinoma); however, expression in benign follicular adenoma was higher than in highly aggressive undifferentiated carcinoma.30