Pulmonary metastases from differentiated thyroid cancer: diagnostic difficulties

We aimed to evaluate and compare the capabilities of various diagnostic methods in detecting lung metastases of differentiated thyroid cancer (DTC). We retrospectively studied 36 patients (mean age 53 years, 33 females and 3 males) with metastases in lungs of DTC (29 papillary DTC and 7 follicular DTC), followed in the radiotherapy department of systemic therapy of State health care facility “Chelyabinsk Regional Clinical Oncology Dispensary” between 2011 and 2014. On chest radiography lung metastases were observed in 13 patients (36 %); in 23 patients (64 %) chest X-ray no revealed lesions in the lungs. Whole body scintigraphy with I-131 was informative in 24 patients (67 %) and did not reveal an increased accumulation of the radiopharmaceutical in the lungs of 12 patients (33 %). Multi-slice spiral computed tomography (MSCT) of the chest was performed in 22 patients (61 %), of whom 21 patients (95 %) had lesions in the lungs from 1.4mm to 20 mm. PET / CT with 18-FDG was performed in 18 of 36 patients (50 %), which showed pathological lesions in the lungs from 3 mm to 26 mm in all 18 patients (100 %) of these 16 patients (88 %) metastatic lesions identified exclusively only with MSCT. Thus, the most sensitive methods in detecting lung metastases are MSCT (95 %), PET / CT with 18-FDG (100 % due to the existence of a regime MSCT) and whole-body scintigraphy with I-131 (67 %). For suspected lung metastases of DTC: 1) chest X-ray should be used as a screening method for the survey; 2) whole body scintigraphy with I-131 should be performed in all patients; 3) MSCT of the chest is the “gold standard” for diagnosis; 4) PET / CT with 18-FDG should not be used in routine practice.