Anaplastic spindle-cell squamous carcinoma arising in association with tall-cell papillary cancer of the thyroid: A potential pitfall

Transformation of a differentiated thyroid carcinoma is an infrequent occur rence and is usually associated with a dismal prognosis. Following a long-s tanding history of papillary carcinoma of the thyroid, the patient in the p resent report developed anaplastic thyroid carcinoma. The anaplastic compon ent initially arose in the setting of papillary carcinoma with tall-cell fe atures, represented a very small proportion of the tumor and was overlooked at the time of the original diagnosis. Several years later the patient dev eloped a recurrent neck mass. Fine-needle aspiration (FNA) of this mass rev ealed a population of atypical spindle cells arranged singly and in papilla ry clusters which lacked the classical cytologic features of papillary carc inoma of the thyroid. Histology of the resected mass revealed an unusual an d recently described subtype of thyroid carcinoma, termed "anaplastic spind le-cell squamous carcinoma," which has been reported as occurring in associ ation with tall-cell papillary carcinoma. The FNA findings of this unusual subtype of anaplastic thyroid carcinoma are presented (C) 1999 Wiley-Liss, Inc.