I-131 uptake in the breast from fat necrosis.

Radioactive iodine I-131 whole-body scintigraphy is used to monitor thyroid cancer metastases after total thyroidectomy. We present a case of a woman who was diagnosed with papillary thyroid cancer and underwent a total thyroidectomy. I-131 scintigraphy revealed abnormal accumulation of radioactive iodine in the right breast causing concern for thyroid cancer metastasis. Mammographic studies confirmed that the abnormal radiotracer accumulation was due to fat necrosis in the breast. I-131 uptake in fat necrosis is a poorly understood process that is not clearly defined in the literature. This case highlights that false-positive uptake of I-131 can mimic metastases of thyroid carcinoma.