Papillary thyroid carcinoma presenting as a functioning thyroid nodule: report of 2 rare cases

Introduction: Autonomously functioning thyroid nodules (AFTNs) are generally benign, whereas papillary thyroid carcinomas (PTCs) are mostly non-functioning. Graves' disease (GD) is the most common cause of hyperthyroidism (HD), followed by hyperfunctional adenoma or Plummer's disease. GD with AFTNs is called Marine-Lenhart syndrome, a relatively rare syndrome. In clinical practice, the presence of HD, AFTNs and PTC at the same time is extremely rare. Case presentation: Case 1: A 55-year-old middle-aged woman with a preoperative diagnosis of GD and HD with right AFTNs. Case 2: A 43-year-old middle-aged woman with a preoperative diagnosis of non-GD and HD with right AFTNs and right PTC. Case 1: Histology showed a 4 cm adenoma with a 1.0 cm PTC in the right lobe and a 0.3 cm PTC in the left lobe. The rest of the thyroid showed typical pathologic GD changes. The postoperative diagnosis was atypical Marine-Lenhart syndrome with bilateral PTC. Case 2: Histology showed a 0.4 cm PTC surrounded by nodular goiter. The postoperative diagnosis was toxic nodular goiter with PTC. Conclusion: This paper covers the relationships among PTC, HD and AFTNs, explains some common and uncommon clinical diagnoses, and reports two rare cases with these three diagnoses. Our ultimate purpose is to remind doctors that when handling nodules or HD, PTC as a diagnosis cannot be excluded. Instead, it is better to perform total or near-total thyroidectomy and intraoperative frozen biopsy or preoperative biopsy examinations to avoid omitting PTC, which needs reoperation.