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Year : 2019  |  Volume : 56  |  Issue : 4  |  Page : 379--380

False positive helmet sign on radioactive iodine-131 scintigraphy

Ramachandran Krishna Kumar1, Arvind Krishnamurthy2, Gomadam Kuppusamy Rangarajan1, Nagarathinam Anandi1, Namasivayam Parvathnathan1,  
1 Department of Nuclear Medicine, Cancer Institute (WIA), Adyar, Chennai, Tamil Nadu, India
2 Department of Surgical Oncology, Cancer Institute (WIA), Adyar, Chennai, Tamil Nadu, India

Correspondence Address:
Arvind Krishnamurthy
Department of Surgical Oncology, Cancer Institute (WIA), Adyar, Chennai, Tamil Nadu

How to cite this article:
Kumar RK, Krishnamurthy A, Rangarajan GK, Anandi N, Parvathnathan N. False positive helmet sign on radioactive iodine-131 scintigraphy.Indian J Cancer 2019;56:379-380

How to cite this URL:
Kumar RK, Krishnamurthy A, Rangarajan GK, Anandi N, Parvathnathan N. False positive helmet sign on radioactive iodine-131 scintigraphy. Indian J Cancer [serial online] 2019 [cited 2020 May 29 ];56:379-380
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A 40 year old woman with no comorbid illnesses was referred to our center for further management of papillary carcinoma of the thyroid. Clinical examination along with ultrasound correlation revealed thyromegaly with multiple hypoehoic nodules, the largest being a 3 cm complex nodule involving the left thyroid lobe and also multiple enlarged left lateral neck nodes that were cytology-proven to be metastatic papillary carcinoma of the thyroid. She underwent an uneventful total thyroidectomy with central compartment neck dissection and left functional neck dissection. Her postoperative histology confirmed the diagnosis of multicentric conventional papillary carcinoma thyroid with minimal extrathyroidal extension. Two central compartment neck nodes and three out of the 20 left lateral neck nodes were positive for metastatic papillary carcinoma with perinodal spread. Her postoperative diagnostic Iodine 131 scan showed local uptake of 2%; her whole body scan was however negative. [Figure 1]a Her postoperative serum thyroglobulin was 0.36, the anti-thyroglobulin antibody was within normal limits. She was subsequently taken up for radioactive Iodine ablation with 55 millicuries of Iodine-131. Her post-therapy scan apart from the local uptake revealed the classical “Helmet Sign,” an artifact caused by diffuse tracer accumulation in the patient's scalp most possibly related to her recent hair dyeing as corroborated with the patient's clinical history. [Figure 1]b This artifact was considered disease-unrelated, taking into account the patient's history, normal levels of serum thyroglobulin throughout and the reduction (Post therapy scan Day 11 [Figure 1]c scan done after a hair wash with a medicated shampoo), and subsequent disappearance of the diffuse increased scalp activity in the follow-up Iodine-131 scans after 6 months. She continues to be disease-free on thyroxine suppression and has normal serum thyroglobulin for over 2 years now.{Figure 1}

The commonly used radioactive Iodine-131 scintigraphy scans in the management of well-differentiated thyroid cancers have a reported a sensitivity ranging from 60-80% and specificity of >90%. In the vast majority of the cases, the false-positive radioiodine distribution is encountered primarily because of physiologic secretions such as accumulation from perspiration or other bodily secretions and distribution in tissues that would normally concentrate the radiotracer, followed by contaminated personal items such as handkerchiefs or jewellery.[1],[2],[3] The diffuse scalp uptake as seen in our patient can most probably be explained because of initial folliculitis and subsequent perspiration because of irritation from the hair dye, leading to an increased distribution of the Iodine-131 along the scalp.[1] Clinicians should be aware of the various causes of false-positive findings in Iodine-131 scans and should take appropriate steps to correctly identify and diligently disregard them when encountered.[1],[2],[3],[4],[5],[6]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.

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