Diagnostic pitfalls of thyroid pathology

The huge amount of information carried to the field of thyroid oncology by immunohistochemistry, cytogenetics and molecular biology did not solve (yet?) the most frequent dilemmas faced by surgical pathologists when dealing with thyroid lesions: differential diagnosis of encapsulated, follicular-patterned tumours with less-than-typical nuclei and equivocal signs of invasiveness; classification of oncocytic (Hürthle cell) tumours; identification of poorly differentiated carcinomas in the background of papillary carcinomas with foci of solid growth pattern and of widely invasive follicular carcinomas; and, finally, cytological and histological diagnosis of metastatic lesions. This review is intended to point out the diagnostic pitfalls in the aforementioned settings and to provide some strategies to deal with them in a practical way.