Association of incidentally detected cold nodule on 99mTcO4- thyroid scintigraphy in Graves’ disease patients & malignancy: A rare phenomenon or cause of concern?

Objectives This retrospective study was designed to determine (1) prevalence of malignancy in incidentally detected cold nodule(s) on thyroid scintigraphy in Graves’ disease (GD) pts & (2) existence of any specific histopathological(HP) pattern and outcome of such pts.

Methods Records of 1346 GD pts (Jan 2004 to Jan 2012) of 99mTcO4- scan were reviewed .Pts with scintigraphically detected cold nodule(s) were included & underwent USG & FNAC of cold nodule for characterization. Thyroidectomy was performed in pts with posi-tive/suspicious FNAC findings for malignancy. Malignancy incidence was confirmed from HP report. I-131 therapy & follow up details were noted.

Results 140/1346 pts (10.4%) had incidentally detected cold nodule.112/140 had confirmed nodule on USG & underwent guided FNAC that showed the nodule as malignant / suspicious for malignancy in 19/112 (17%) pts. 19 FNAC +ve pts (M:F-8:11,Age 25-68 yrs) underwent Total Thyroidectomy. HP was reported as PCT in 13/19, multifocal micro pap Ca 4/19 & FCT in 2/19 pts. Lymph nodal mets & HP high risk factors noted in 3/19 & 2/19 pts resp. None had distant metastases. 15/19 pts (79%) underwent residual thyroid I-131 ablation (range 2590-3700 MBq) after risk stratification. On follow-up, these pts had negative I-131 scan & normal Tg levels suggesting complete ablation. No scintigraphic /biochemical evidence of disease noted for median follow up period of 20 months (range 13-75 months).

Conclusions Incidence of malignancy in cold nodule with GD background was 17% & it was higher than average general reported incidence of 10% malignancy in cold nodule detected on thyroid scintigraphy. PCT is most common histological variant & prognosis of subset of such pts is compara-ble to other DTC pts and they respond well to I-131 treatment.