Kunihiro Nakada, Presenter: Nothing to Disclose

Nozomu Fujimoto MD, PhD, Abstract Co-Author: Nothing to Disclose

Hiroki Sugie MD, Abstract Co-Author: Nothing to Disclose

Masayuki Sakurai, Abstract Co-Author: Nothing to Disclose

Primary thyroid lymphoma (PTL) arises from Hashimoto’s thyroiditis(HT), which could show diffuse thyroid FDG uptake. The aim of the study was to compare findings of FDG PET/CT with those of ultrasound (US) in PTL

Total of 42 patients with PTL were enrolled. All patients underwent neck US, US-guided core needle biopsy, and PET/CT using FDG. Thyroid function at FDG PET/CT was euthyroid in 25, hypothyroid in 15, hyperthyroid in 2. Specimen of core needle biopsy was subjected to immunohistochemical staining (CD20,CD3,CD79a,Ki-67, etc.) along with H-E staining. IgH re-arrangement was analyzed by PCR. All patients were fasted overnight prior to injection of FDG. On PET/CT images, FDG uptake in the thyroid was categorized as nodular or diffuse by visual interpretation. Additionally, FDG uptake was semi-quantitatively determined in form of SUVmax. US findings was categorized as hypoechoic nodular or diffuse non-homogenous low echo.

Pathological diagnosis was MALT lymphoma in 32 and DLBCL in 10. clinical stage was IE in 27 , IIE in 12, IIIE in 2 and IV E in 1. In PTL, FDG uptake was nodular in 14 and diffuse in 28. There was no significant difference in SUVmax between nodular uptake and diffuse uptake (6.7± 2.5 vs. 8.3 ±2.8). On US, 16 showed hypoechoic nodular lesion while the remaining 27showed diffuse non-homogenous low echo. Surprisingly, 13(46%) out of 28 with diffuse FDG uptake showed nodular lesion on US. There no patients who showed diffuse non- homogenous low echo despite nodular FDG uptake.

our study, about 50% of PTL with diffuse FDG uptake had nodular appearance on US. Thus, combination of FDG-PET.CT and US should be helpful in assessment of intrathyroidal lesions from PTL.

To evaluate accurate intrathyroidal status of PTL, combination of FDG PET/CT and US is higly recommended

Nakada, K, Fujimoto, N, Sugie, H, Sakurai, M, Comparison of FDG-PET/ and US in Diagnosis of Primary Thyroid Lymphoma.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14019659.html