Papillary carcinoma constitutes about two thirds of thyroid malignancies in adults and nearly all thyroid malignancies in children. Females are affected at least three times as often as males and the peak incidence is between 30y and 45y.
Histologically, the tumour forms a complex branching papillary structure with a fibrovascular stroma, often containing calcified 'psammoma bodies'.
Tumours vary over a wide range of epithelial dysplasia between apparently benign and obviously malignant.
Whatever the degree of dysplasia, the tumours grow slowly.
Papillary carcinomas are microscopically multicentric in about 80% of cases and about one third affect both lobes; this is important in planning treatment.
The tumour occasionally invades locally into trachea or oesophagus. Metastasis is to central cervical and later lateral cervical LNs and only rarely to distant sites such as lung or bone.
By presentation, LN are involved in about 40% of patients (90% in children).
LN enlargement is often the sole presenting feature and the histology of involved LNs is so close to normal thyroid tissue that at one time this condition was known as 'lateral aberrant thyroid'.
The prognosis of papillary carcinoma is the best of all thyroid carcinomas with only about 10% of patients dying of the tumour after 10y; it is remarkable that survival is hardly prejudiced by the presence of LN mets.
Symptoms and signs
Papillary ca presents as a slow-growing thyroid nodule.......... incomplete
Management
Total thyroidectomy because of the high risk of other foci within the gland.
Palpable cervical nodes are removed at the same operation. The operation is no more difficult than subtotal thyroidectomy but carries a higher risk of post-op hypoparathyroidism.
Total thyroidectomy has the added advantage that recurrent local disease, LN or distant mets can then effectively be treated with radioiodine (131I). This requires a very high TSH level which only occurs if no normal thyroid tissue remains.
A further advantage is that plasma thyroglobulin can then be used as a tumour marker to detect recurrent disease.
After treatment, hormone replacement is necessary to keep TSH close to zero to minimise the risk of stimulating any residual malignant cells.
Since papillary ca progress so slowly and only 15% develop contralateral lobe recurrence, some surgeons prefer to retain one thyroid lobe if the primary tumour is small and there are no palpable or isotope-detectable nodules. Their reasoning is that any further tumours can be removed later without reducing life expectancy.
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