Introduction: Chronic lymphocytic thyroiditis (LT) is a very common condition, and its coexistence with papillary thyroid carcinoma has often been reported. Analytical and echographic challenges must be kept in mind in the follow-up of patients with both these disorders.
Case report:: We present the case of a woman with a history of multinodular goitre who underwent left thyroidectomy and isthmectomy at the age of 43, with the histopathological finding of papillary microcarcinoma associated with nodular hyperplasia and LT. Her follow-up included regular cervical and thyroid ultrasound and thyroglobulin (Tg) and antithyroglobulin autoantibodies (TgAbs) measurements. The remaining right thyroid lobe had a micronodular appearance on ultrasound; TSH was in the normal range; TgAbs were positive; Tg was undetectable. After 8 years of follow-up, ultrasound revealed a suspicious cervical lymph node. A fine-needle aspiration biopsy (FNAB) was performed, with the Tg concentration of FNAB washout liquid being 36 ng/ml and cytology revealing aspects of metastasis from papillary thyroid carcinoma. She underwent completion thyroidectomy and lymph node dissection. Histopathology revealed a 12 mm papillary carcinoma in the right thyroid lobe, with extension to perithyroidal adipose tissue. The patient was subsequently admitted for radioiodine remnant ablation.
Conclusions: In patients with thyroid papillary microcarcinoma who have had only partial thyroidectomy and are positive for TgAbs, neither Tg nor TgAbs can be used reliably; regular careful ultrasound evaluation is essential in the follow-up of these patients. On the other hand, due to known alterations in thyroid gland structure, LT may cause diagnostic performance of thyroid ultrasound to be inferior in detecting suspicious nodules. This case report brings attention to the different difficulties found in the follow-up of patients with coexisting LT and thyroid papillary carcinoma.