Clinical History
Rapid thyroid enlargement.
Imaging Findings
This patient had initially presented with a long standing neck lump, which had shown typical features of multinodular goitre on ultrasound. He subsequently presented at the outpatient clinic with a
rapid enlargement of the right side of the gland over one month. He denied any history of hoarse voice, but flexible nasendoscopy suggested impaired movement of the right vocal cord. A CT scan of the
neck and chest with intravenous contrast was performed. The CT scan demonstrates a mass enlarging the right lobe of the thyroid containing irregular areas of non-enhancement consistent with necrosis.
This mass shows local infiltration, extending through platysma muscle to the subcutaneous fat and involving the right sternomastoid and longus colli muscles and early invasion of the hypopharynx on
the right side. An amorphous calcification is present in the mass. The tumour encases the carotid sheath, and extensive thrombus is demonstrated within the internal jugular vein. The larynx is
displaced to the left and there is evidence of a right recurrent laryngeal nerve palsy with a redundant right areyepiglottic fold and medialisation of the vocal cord. Palliative treatment with
radiotherapy was given, despite this there was progressive tumour enlargement and the patient developed airway compromise and died approximately four months after the time of diagnosis.
Discussion
As in this case, anaplastic carcinoma typically presents in an elderly patient with a rapidly growing neck mass. The prognosis is generally dismal with median survival time of 4 to 12 months from the
time of diagnosis. Death is most commonly due to local growth resulting in airway compromise. Prognosis is worst in those patients with a tumour over 6cm in size and those with distant metastases.
Imaging allows assessment of tumour extent and potential resectability. It identifies involvement of key structures within the neck and may detect metastases. Typical imaging features include a
locally invasive mass obliterating fat planes and directly infitrating local structures such as muscle, larynx and oesophagus. There may be involvement of the carotid sheath, with vascular
compression, thrombus or direct invasion. Compromise of the vagus nerve directly, or the recurrent laryngeal nerve will lead to a vocal cord palsy, which may be appreciated on imaging by
medialisation of the cord and redundancy of the aryepiglottic fold. Approximately 40-75% of patients will have metastatic neck nodes at the time of diagnosis and necrosis within these and the primary
tumour is very common. Amorphous calcification (as in this patient, see fig 1) is also a common feature. Distant metastases are seen in about 50%. Differential diagnoses include lymphoma (more common
in females), which may be indistinguishable from anaplastic carcinoma on the basis of history and imaging,although unlike anaplastic tumours necrosis and calcification are rare. Other cellular forms
of thyroid carcinoma tend to be less diffusely infiltrative and slower growing, although poorly differentiated forms may exhibit more aggressive behaviour.
Differential Diagnosis List
Anaplastic carcinoma of the thyroid.
Final Diagnosis
Anaplastic carcinoma of the thyroid.
