Differentiated thyroid carcinoma, intermediate type.

A thyroid carcinoma showing histological and histochemical features of both follicular and parafollicular cell carcinoma was diagnosed in a 56 year old male. Previously the two cell types have been considered to be derived from embryologically distinct and separate precursors. The unusual combination of the two cell types in this tumour suggests the possibility that the cell lines may be derived from a common stem cell with the potential of differentiating into both follicular and parafollicular cells. The tumour was aggressively invasive and had metastasized widely to lymph nodes at the time of presentation. It represents an example of the recently described entity of differentiated thyroid carcinoma of intermediate type.