Differentiated thyroid tumours of follicular cell origin comprise follicular adenoma, follicular carcinoma and papillary carcinoma. The main areas of diagnostic difficulty are the distinction of follicular adenoma and carcinoma and the differentiation between follicular adenoma and follicular variant of papillary carcinoma. This presentation will address these issues and will discuss the use of the categories ‘well‐differentiated carcinoma, not otherwise specified (WDC‐NOS)’ and ‘well differentiated tumour of uncertain malignant potential (WDT‐UMP)’.
There is evidence that prognosis is worse in widely invasive than in minimally invasive follicular carcinoma. The criteria for differentiating these subgroups will be discussed. The prognostic relevance of subclassifying papillary carcinoma will also be addressed.
The diagnosis of poorly differentiated carcinoma has been a matter of debate and this will also be included. Relevant immunohistochemical and molecular genetic aspects will be presented.