A rare challenging macrofollicular thyroid carcinoma: a case report

Abstract Background Macrofollicular variant of papillary thyroid carcinoma (MFV-PTC) is an exceptionally rare subtype that mimics benign colloid nodules. Due to its insidious microscopic appearance, it poses a significant risk of cytological misdiagnosis. Case presentation A 38-year-old woman presented with a suspicious solid thyroid nodule. Two consecutive fine-needle aspiration (FNA) biopsies were reported as Bethesda Category II (Benign). A third FNA finally suggested malignancy, and subsequent histopathology confirmed MFV-PTC. Following total thyroidectomy and radioactive iodine ablation, the patient remains disease-free at 12-month follow-up. Conclusions MFV-PTC is a rare but critical differential diagnosis in follicular lesions. This case highlights the potential for false-negative cytology and the importance of clinical correlation in managing macrofollicular thyroid nodules.