(Case 1). 2a. Post radioiodine ablation scan showing abnormal 131I accumulation in the right upper neck and thyroid bed. There is a linear abnormality to the right of the midline of the upper chest extending inferiorly suggestive of residual tumour in the SVC. 2b. Post radioiodine therapy scan showing a focus of intense 131I accumulation in the right upper mediastinum suggesting tumour at the root of the SVC. Marked improvement compared with initial scan (2a).