Abstract
A 58-year-old man presenting with acute development of a left neck mass was referred to our department with a suspicion of anaplastic thyroid carcinoma. On physical examination, an elastic-hard and ill-defined tumor in the entire left thyroid lobe was palpated. On blood biochemical examinations, the thyroglobulin level was as high as 4,970 ng/mL. Ultrasonogram revealed a 68-mm ill-defined heterogeneous hypoechoic tumor in the left thyroid lobe. A contrast-enhanced CT scan showed the heterogeneously enhanced tumor and bilateral cervical lymph node swellings. A core-needle biopsy revealed hyperplasia of spindle-shaped cells with clear nucleolus. The Ki-67 index was more than 50%. The mitotic figure was 6/10 HPFs. Necrosis was present. We thus made the diagnosis of anaplastic thyroid carcinoma (T3aN1bM0, Stage IVB). Total thyroidectomy, peritracheal dissection and left #6 sampling were performed. On the resected specimen, the section of the tumor was cystic and hemorrhagic and/or necrotic portions accounted for about 80% of the inner portion, which included infarction and ischemic change. In the periphery of the tumor, follicular structure was confirmed, indicating the tumor to be a follicular tumor ; and there was a part of capsular invasion. Consecuently we diagnosed the case as minimally invasive follicular thyroid carcinoma (pT3aN0M0, Stage II). The spindle-shaped cells seen at the tumor periphery preoperatively were associated with infiltration of inflammatory cells and granuloma, so we considered that reactive changes might occur. Here we present this case finally diagnosed through a rare process.
