We report the case of a 59-year-old man with a two-month history of a fast-growing, left-sided neck mass and a 5 mm nodule over a thyroid mass at the site of fine needle aspiration cytology performed four weeks earlier. Histopathological studies confirmed anaplastic carcinoma of the thyroid and cutaneous needle track seeding of the primary tumour. The patient succumbed to extensive disease 10 weeks after initial diagnosis. To our knowledge, this is a rare report of implantation of anaplastic thyroid carcinoma along the track of fine needle aspiration. Some factors involved in needle track seeding are: needle size; number of passes; withdrawing the needle without releasing suction; injecting the tumour at time of biopsy; and inherent characteristics of the lesion (e.g. number of cells dislodged, adhesiveness of cells, amount of stroma present, enzymes released and immunologic characteristics).
