Diagnosis of carcinomas of extrathyroidal origin with fine needle aspiration cytology of the thyroid: An experience from a tertiary care center in South India

Intrathyroidal metastasis and direct extension of extrathyroidal malignancies can present with palpable thyroid nodules or may be detected as suspicious nodules in a thyroid scan. They can lead to diagnostic difficulty in fine needle aspiration cytology (FNAC) of the thyroid, especially in the absence of any previous history of such malignancies. Here we report an interesting case of intrathyroidal metastasis, which was initially suspected as a primary carcinoma of the thyroid; along with a short summary of a series of 11 cases of carcinomas of extrathyroidal origin, diagnosed in the FNACs of thyroid over the past three years in our institute. Knowledge of the potential diagnostic pitfalls in thyroid FNAC, a proper clinical evaluation, and judicious use of the ancillary techniques will help to attain a proper diagnosis.