Posttraumatic Scab on 131I Whole-Body Scan-A False-Positive Finding

Unusual 131 I Uptake Caused by Paronychia in a Patient With Papillary Thyroid Cancer

ABSTRACT

A 33-year-old woman was referred for radioiodine 6 months after total thyroidectomy and neck dissection for papillary thyroid cancer. Posttherapy whole-body 131 I scintigraphy showed not only the known activity in the neck but also accumulated activity in both feet. SPECT/CT revealed focal uptake in bilateral great toenails. On further clinical evaluation and follow-up, the patient was diagnosed as paronychia of the great toenails.

Radioiodine whole body scan pitfalls in differentiated thyroid cancer

PURPOSE

whole body scan (WBS) performed following diagnostic or therapeutic administration of I-131 is useful in patients with differentiated thyroid carcinoma. However, it can be falsely positive in various circumstances. We aimed to report a series of pitfalls in a clinical perspective.

METHODS

A search in the database PubMed utilizing the following terms: "false radioiodine uptake" and "false positive iodine 131 scan" has been made in January 2023. Among the 346 studies screened, 230 were included in this review, with a total of 370 cases collected. Physiological uptakes were excluded. For each patient, sex, age, dose of I-131 administered, region and specific organ of uptake and cause of false uptake were evaluated.

RESULTS

370 cases of false radioiodine uptake were reported, 19.1% in the head-neck region, 34.2% in the chest, 14.8% in the abdomen, 20.8% in the pelvis, and 11.1% in the soft tissues and skeletal system. The origin of false radioiodine uptake was referred to non-tumoral diseases in 205/370 cases (55.1%), benign tumors in 108/370 cases (29.5%), malignant tumors in 25/370 cases (6.7%), and other causes in 32/370 cases (8.7%).

CONCLUSIONS

WBS is useful in the follow-up of patients with differentiated thyroid carcinoma, however it can be falsely positive in various circumstances. For this reason, it is critically important to correlate the scintigraphic result with patient's medical history, serum thyroglobulin levels, additional imaging studies and cytologic and/or histologic result.

False-Positive 131 I Uptake After Posttraumatic Scab in a Patient With Papillary Thyroid Carcinoma

ABSTRACT

A 41-year-old woman with right papillary thyroid carcinoma underwent 131 I therapy (3.7 GBq). Posttherapy whole-body scintigraphy acquired 2 days later revealed a focus of intense activity in the anterior aspect of the left knee. The activity corresponding to the posttraumatic scab. Posttraumatic scab should be considerable a cause of false-positive whole-body scintigraphy findings.

Radioactive Iodine Uptake in Postoperative Seroma: A Cause for False Positivity

Besides the known physiologic uptake of ¹³¹I, the literature describes various false-positive findings on ¹³¹I scans in benign lesions, inflammation, traumatic sites, and postsurgical sites, to name a few. However, to the best of our knowledge, no study has shown false-positive uptake of ¹³¹I in a postoperative seroma at the postsurgical site. We describe such a case here.

An Unusual False-Positive Uptake of Radioiodine Caused by Posttraumatic Superficial Scab

ABSTRACT

A 22-year-old man with a history of recurrent papillary thyroid cancer underwent 131I therapy. Posttherapeutic whole-body scintigraphy was performed 5 days after administration of 5.5 GBq of 131I. The scintigraphy revealed increased activity in the left elbow. On physical examination, the patient had posttraumatic superficial scab at the site of the abnormal activity.

An Unusual False-Positive Uptake of Radioiodine Caused by Breast Implants

ABSTRACT

A 40-year-old woman with a history of papillary thyroid cancer underwent ablative 131I therapy. Postablation whole-body 131I scintigraphy revealed not only increased activity in the thyroid bed but also in the anterior part of the chest. SPECT/CT images localized the activity in the bilateral breast implants.