We present the case of a 73-year-old woman, who presented with ascites and a history of left radical hemithyroidectomy for localized follicular thyroid carcinoma (FTC) 28 years ago. Computed tomography (CT) scanning of her body revealed extensive metastatic lesions. An omental biopsy showed features suggestive of thyroid follicular epithelial cancer. Serum thyroglobulin was raised at 127 μg/l. She died before the biopsy result was received. Two years before presentation, a bilobed nodule was noted in the superior mediastinum measuring 3.5×1.5 cm, on a CT chest organized by her primary care physician to investigate breathlessness. A thyroid uptake scan that followed had shown normal uptake in the right thyroid remnant and a high uptake in this structure, suggestive of ectopic thyroid tissue. No further action was taken at the time. A retrospective review of her thyroid function tests showed that serum thyrotropin (TSH) had never been suppressed and she had untreated hypothyroidism 3 years before her presentation. We suspect that she may have harboured FTC cells from the primary lesion in the ectopic gland or developed a de-novo lesion within it that spread due to inadequate TSH suppression. A timely diagnosis by a positron emission tomography (PET) or radio-iodine scan would have provided grounds for consideration of curative or palliative radio-iodine ablation.
Thyroid cancer, the commonest endocrine cancer, is relatively rare in comparison to other cancers (<1% of all cancers). It is therefore least suspected in an individual presenting with metastatic disease and an unknown primary. Follicular thyroid cancer is the second most common differentiated thyroid cancer. Current practice involves total thyroidectomy (older patients, high-risk cases), followed by radio-iodine ablation and long-term TSH suppression. This case emphasizes the importance of long-term follow up of this condition, in order to monitor for recurrence and to maintain TSH suppression.