Difficulties in diagnosis of Riedel's thyroiditis on aspiration cytology: A case report and brief review of the literature.

Riedel's thyroiditis (RT) is a rare disorder characterized by extensive fibrosis extending to the extrathyroidal tissues. An elderly male presented with diffuse moderate thyromegaly and hoarseness of voice for two years. Radiology showed extrathyroidal extension around trachea with compression and deviation suggestive of malignancy. Thyroid was hard and non tender. Ultrasound guided Fine Needle Aspiration (FNA) from multiple foci on both sides using thinner needle yielded moderately cellularity showing follicular cells, lymphoplasmacytic infiltrate, scant colloid and fibrous tissue fragments. Hurthle cells were absent. Adiagnosis of chronic thyroiditis was given with possibility of RT in view of clinical and radiological findings. A core biopsy showed similar picture as cytology. Guided FNA from multiple foci using thinner needle helped to obtain adequate material allowing a confident diagnosis. This case adds to the meagre literature available on the cytologic diagnosis of RT and highlights the diagnostic challenge due to suspicious radiology findings.