Endocrine Abstracts

Case history: A 70 year old man presented with a six month history of sore throat and dysphagia. His past medical history included Type 2 diabetes and dysarthria due to tracheomalacia following tracheostomy at the age of 40 when he was involved in a road traffic collision. Initially he was diagnosed with gastroesophageal reflux, but symptoms did not settle with proton pump inhibitor medication. He as therefore referred to the ENT team for further evaluation.

Investigations: Fibreoptic assessment (rigid oesophagoscopy and tracheal bronchoscopy) by ENT team showed significant tracheal stenosis from external compression with normal pharynx and larynx structures. He underwent a thyroid CT scan which revealed a large goitre with severe retrosternal extension with anterior and posterior compression of the trachea. His thyroid function test was normal. He underwent left hemi thyroidectomy. Histology revealed metastatic clear cell renal carcinoma (CCRC) grades 2–3. Staging CT scan of the chest, abdomen and pelvis identified a 5 cm right kidney upper lobe mass with paraaortic lymph node enlargement with lung and adrenal metastatic lesions, making it a T3aN1 renal cell carcinoma.

Results and treatment: The patient underwent right sided laparoscopic nephrectomy and total thyroidectomy. He also received tyrosine kinase inhibitor therapy for systemic treatment. Unfortunately his disease progressed, with increase in size of lung and lymph node metastasis and new pancreatic deposits.

Conclusions and points for discussion: CCRC is the most common subtype of renal cell carcinoma – up to 75% of cases.

Metastatic malignancy in the thyroid gland from any primary cancer is rare (2–3% of thyroid malignancies) despite its good blood supply, and the commonest primary cancer that metastasizes to the thyroid is renal cell cancer (25–50% of thyroid metastasis).

Most thyroid metastases occur several years after treatment of primary cancer – on average 9 years. It is unusual for thyroid metastasis to be the first presentation on (despite of our case).

Thyroid imaging is not useful in differentiating between primary and secondary thyroid malignancies and CT imaging is not usually undertaken unless there are compressive symptoms.

FNAC is a good tool to establish definitive diagnosis but occasionally it is difficult distinguish metastasis from primary tumors of thyroid.

If FNAC is inconclusive, immunohistochemistry can help in the differential diagnosis. Thyroid metastasis should be considered in patients.