Thyroid nodule with Hashimoto thyroiditis in childhood - a challenging experience

Area of Science:

• Endocrinology
• Oncology
• Pathology

Background:

• Fine-needle aspiration biopsy (FNAB) is the primary preoperative tool for diagnosing thyroid nodules.
• Autoimmune thyroiditis can present with lymphocytic infiltration, potentially mimicking benign changes in FNAB cytology.
• Thyroid nodules in children warrant careful evaluation due to a higher risk of malignancy.

Observation:

• An 8-year-old girl presented with a thyroid mass and subclinical hypothyroidism with high anti-thyroid peroxidase antibodies.
• Initial FNAB showed reactive changes and inflammation, interpreted as non-malignant.
• Despite L-thyroxine treatment, the nodule increased in size, and repeat FNAB was non-diagnostic.

Findings:

• Post-lobectomy pathology revealed papillary thyroid carcinoma, follicular variant with insular growth components.
• The initial FNAB result was a false-negative, likely due to autoimmune thyroiditis obscuring malignant cells.
• Concomitant autoimmune thyroiditis complicated the cytological interpretation of the thyroid nodule.

Implications:

• This case underscores the challenge of FNAB interpretation in the presence of autoimmune thyroiditis.
• It emphasizes the need for clinical and imaging correlation when FNAB results are discordant with suspicion.
• Management strategies and prognosis for pediatric thyroid cancer with autoimmune thyroiditis require careful consideration.