In some cases it may be difficult to differentiate between a benign and a malignant lesion, particularly as there may be overlapping cytological features. Follicular neoplasms are often reported in this category, it being difficult to differentiate between follicular/Hürthle cell carcinomas and adenomas cytologically. 'Suspicious' cases may be: suspicious for papillary carcinoma, suspicious for a follicular neoplasm, suspicious for a Hürtle cell neoplasm. 60% of nodules reported as 'suspicious for papillary carcinoma' are malignant, in contrast with only 10-15% of nodules reported as 'suspicious for follicular or Hürthle cells neoplasms'.
Definition of suspicious:
- All follicular lesions with cytological atypia
- All papillary lesions without the nuclear criteria of papillary thyroid carcinoma
- All pure Hürthle cell lesions
- All monomorphic lymphoid lesions