Epidermal Cyst Mimicking Thyroid Cancer Metastasis.

A 26-year-old woman with pulmonary metastasis of thyroid cancer underwent a total thyroidectomy and cervical lymph node dissection followed by 2 courses of 131I therapy. The posttherapeutic whole-body scan after the second dose of 131I therapy showed diffuse tracer uptake in both lungs. Besides this, there is a local abnormal radiotracer uptake in the left axillary region. SPECT/CT images localized this abnormal radioactivity in a subcutaneous, oval-shaped, approximately 2.2-cm slightly hyperdense lesion, which was pathologically confirmed as an epidermal cyst.