A 25-year-old woman with known Hashimoto's thyroiditis for 5 years presents with rapid enlargement of her goitre over 3 months and new hoarseness. Ultrasound shows a 5 cm hypoechoic mass with punctate calcifications replacing the right lobe. The most important investigation to exclude the suspected diagnosis is:

• A Thyroid function tests
• B Radioactive iodine uptake scan
• C Serum thyroglobulin level
• D Core needle biopsy (not FNA) ✓

Explanation

The clinical picture (Hashimoto's thyroiditis with rapid goitre enlargement) raises suspicion for primary thyroid lymphoma, most commonly a diffuse large D-cell lymphoma or MALT lymphoma. FNA often yields insufficient tissue for lymphoma diagnosis. Core needle biopsy or open biopsy is preferred for definitive diagnosis. RAI uptake scan would be cold but is non-specific. Serum thyroglobulin is irrelevant for lymphoma.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.