Parathyroid adenoma mimicking bethesda class III follicular thyroidal lesion: A case report

Introduction and importance

Although the majority of thyroid lesions are benign, diagnostic workup including fine needle aspiration biopsy cytology is important to rule out cancerous lesions. However, cytological findings may pose challenges in interpretation because of similarities in cytomorphological features between certain thyroid nodules and parathyroid tissue. Similarly, parathyroid lesions may go unnoticed for a long period of time because they are misinterpreted as thyroid lesions and patients with parathyroid lesions are typically oligo- or asymptomatic for a long period of time.

Case presentation

We present the case of a 57-year-old female patient who was under observation for a hormone inactive mildly suspicious thyroid nodule for eight years before the suspected thyroid nodule was found to be a parathyroid adenoma. Repeated fine needle aspiration biopsies showed cytomorphological features of Bethesda Class III thyroid nodules and the patient was asymptomatic throughout all consultations. Finally, a pathological hip fracture and symptomatic kidney stone prompted further diagnostic work-up, confirming primary hyperparathyroidism and exposing the suspected thyroid lesion for a parathyroid adenoma. After focused parathyroidectomy the patient fully recovered.

Clinical discussion

Systematic blood sampling for Calcium and parathyroid hormone levels, which has to become part of the usual work up for suspicious thyroid nodules, may have exposed the diagnosis earlier preventing secondary complications.

Conclusion

This case highlights one of the major pitfalls in ultrasound interpretation and fine needle aspiration biopsy of the thyroid gland. Physicians need to be aware of these difficulties during the diagnostic work-up.