Fine needle aspiration wash out for thyroglobulin determination in the differential diagnosis of lung lesions

Purpose: Distant metastasis from papillary thyroid cancer is rare, and the more frequent site is neck and bone. During follow-up after surgery new distant lesions could appear, while Tg levels remain normal. When suspicious lesions are superficial, fine needle aspiration is the first choice. In case of deeper localization, the diagnosis could need more invasive procedure, such as in case of lung nodules. Methods: We report a case of a patient with a lung lesion suspicious for metastasis from papillary thyroid cancer. The patient underwent thyroidectomy and radioiodine 10 years before and after 2 years of follow-up was submitted to right cervical lymphadenectomy for nodal recurrence. During the following 5 years Tg values on TSH suppressive treatment ranged 3.7–5.4, always with negative TgAb and negative neck US. CT scans showed the presence of a single nodule in the left lung with subpleuric localization, progressively increasing in size. A CT-guided fine needle aspiration was performed. Results: The Tg levels measured in the washout out of the Chiba’s needle (386 ng/ml) provided an unequivocal demonstration of the thyroid origin of the nodule. Conclusions: Thyroglobulin measurement in the specimen obtained from CT-guided fine needle aspiration is a useful and effective tool to diagnose lung metastasis from thyroid cancer. This procedure could avoid a surgical approach that is more invasive and potentially detrimental for the patient.