Rare Mixed Thyroid Carcinomas: A Report of Two Cases

Introduction: thyroid cancers constitute 0.5%- 1% of all cancers of which differentiated cancers are most common. mixed thyroid carcinomas are rare entities comprising only 0.5% of thyroid cancers. these tumours pose challenges in diagnosis by fine needle aspiration cytology. case report: here, we present two rare cases of these mixed thyroid carcinomas. the first is that of a 21 year old female diagnosed with medullary thyroid carcinoma by the method of fine needle aspiration cytology (fnac). she underwent definitive surgical treatment. final histopathology revealed diagnosis of a nodular tumour with mixed features predominantly medullary carcinoma with areas of follicular carcinoma, confirmed on immunohistochemistry. second report is that of a 45-year- old female diagnosed as medullary thyroid carcinoma on fine needle aspiration cytology (fnac). definitive surgical treatment was performed. histopathology showed a mixed tumour with medullary and papillary components as confirmed through the process of immunohistochemistry. conclusions: the knowledge of these rare carcinomas is important in avoiding a dilemma in management of this condition. detection of these mixed tumours is difficult by fnac. the definitive treatment essentially requires recognition of medullary component. we re-emphasize the importance of immune-histochemistry in arriving at an accurate diagnosis.