False Positive Result in the Whole-Body Scan with 131-I in the Follow-up of Differentiated Thyroid Cancer: The Fistula Tract Accompanied by the Suture Granuloma

Zuhal Kandemir ,Elif Özdemir ,Şemsi Mustafa Aksoy ,Cevdet Aydın ,Nilüfer Yıldırım Poyraz ,Şeyda Türkölmez

doi:10.12996/gmj.2016.49

Abstract

The role of radioiodine-131(I-131) Whole- body scan (WBS) is crucial regarding the management of patients with differentiated thyroid carcinoma (DTC) in detecting normal thyroid remnants and recurrent or metastatic disease. Although I-131 is a sensitive marker for detection of thyroid cancer, radioiodine uptake is not specific for thyroid tissue. According to several reports, various tissues or non-thyroidal pathologic processes were associated with false-positive WBS with radioiodine. In this case report we reported that the false positive result was present due to the fistula accompanied by the suture granuloma. A 47 year-old woman underwent total thyroidectomy for papillary thyroid carcinoma.A false-positive iodine uptake in the midline neck was determined by a diagnostic I-131 whole body scan. I-131 whole body scan was correlated with ultrasonography (US) and computed tomography (CT) imaging features, biochemical data, clinical history, and physical examination. The lesion was demonstrated to be a fistula tract accompanied by the suture granuloma. The false- positive findings in the I-131 whole-body scan should be confirmed with other imaging modalities, available biochemical data, clinical history, and physical examination in order to avoid unnecessary treatments.

Highlights

The role of I-131 Whole- body scan (WBS) is crucial regarding the management of patients with differentiated thyroid carcinoma (DTC) in detecting normal thyroid remnants and recurrent or metastatic disease
Various tissues or non-thyroidal pathologic processes were associated with falsepositive WBS with radioiodine [1,2,3,4] In our report, the patient is presented with a false-positive uptake caused by the fistula accompanied by the suture granuloma in postoperative thyroid bed
To the best of our knowledge, different false-positive results in I-131 WBS have been described, it is an interesting case of this kind in the literature

Summary

INTRODUCTION

The role of I-131 WBS is crucial regarding the management of patients with DTC in detecting normal thyroid remnants and recurrent or metastatic disease. Various tissues or non-thyroidal pathologic processes were associated with falsepositive WBS with radioiodine [1,2,3,4] In our report, the patient is presented with a false-positive uptake caused by the fistula accompanied by the suture granuloma in postoperative thyroid bed. At the time of diagnostic scan, the stimulated Tg level was 0,187 ng/mL, Anti-Tg was 159,9 U/mL and US showed that there were macrocalcifications at the lateral part of the bilateral thyroid region consistent with postoperative suture materials. The stimulated Tg and Anti-Tg levels were undetectable in the 1st year of follow-up During this period, the radioiodine accumulation at the thyroid bed persisted (Figure 1B-1D). CT images revealed fistula tract appearance at the isthmic level of thyroid bed (Figure 2B)

DISCUSSION

CONCLUSION