The standard surgical treatment for highly differentiated papillary thyroid cancer > 10 mm according to recent national and international guidelines, is total thyroidectomy and central lymphnode clearance, and for patients with cytology indicating thyroid neoplasia of unclear malignant potential hemithyroidectomy on the side of the tumour.

The study investigates if the sentinel lymphnode (SN)

• Reliably (with high sensitivity and specificity), can predict the pathological findings of the lymphnodes in the central compartment in patients with highly differentiated papillary thyroid cancer
• Is useful to aid in the final diagnosis and staging of thyroid neoplasias of unclear malignant potential, and could be used to select patients for further central lymphnode revision.

The standard surgical treatment for highly differentiated papillary thyroid cancer > 10 mm according to recent national and international guidelines, is total thyroidectomy and central lymphnode clearance, and for patients with cytology indicating thyroid neoplasia of unclear malignant potential hemithyroidectomy on the side of the tumour.

There are however a number of clinical problems with these approaches:

• For patients with papillary thyroid cancer, a significant proportion will receive unnecessary extensive surgical treatment
• In papillary thyroid cancer, central lymphnode clearance increases the risk for complications, especially the risk for hypoparathyroidism.

According to a Scandinavian survey (Scandinavian Quality Register for Thyroid- and Parathyroid Surgery; www. thyroid-parathyroidsurgery.com),16 % of patients with unclear follicular neoplasia, will have a final histological diagnosis of thyroid cancer, and in half of them, this cancer will be of the papillary subtype. In patients with preoperatively suspected, but not proven malignancy by cytology, 30 % will receive a final histological diagnosis of thyroid cancer, and in these patients, 70 % will be of the papillary subtype. Typically these patients will undergo a second operation with a contralateral hemithyroidectomy. In many cases, due to risk for complications, central lymphnode clearance is avoided in these cases. Therefore, the staging of the cancer will be incomplete, and some patients will receive suboptimal surgical treatment.

The study is designed to compare SN investigation with the final histology of the central lymphnodes:

• Pretracheal and bilateral paratracheal for patients with preoperatively diagnosed papillary thyroid cancer
• Pretracheal and ipsilateral paratracheal for tumours of uncertain malignant potential on cytology

The identification of SN will be aided by preoperative ultrasound guided injection of 99m- Tc- nanocolloid albumin in the thyroid tumour. The results of the histological investigation of SN will be compared to that of the results from the central lymphnode clearance.

Inclusion Criteria:

• Patients with first time surgery for proven papillary thyroid cancer > 10 mm
• Patients with first time surgery for a cytologic diagnosis of follicular neoplasia or suspected (not proven) malignancy

Exclusion Criteria:

• Age below 18 years
• Pregnancy or lactation
• Inability to understand written and oral information or to comply with scheduled follow-up

- Patients diagnosed and operated for papillary thyroid cancer > 10 mm at the Department of Surgery, Skåne University Hospital, Lund, Sweden

_ Patients with diagnosed and operated for a thyroid tumour of unclear malignant potential at the Department of Surgery, Skåne University Hospital, Lund, Sweden