Evaluation of lymphatic drainage of cold thyroid nodules with intratumoral injection of Tc-99m nanocolloid.

Abstract

The lymphatic system may show variations throughout the entire body. Knowledge of the variations and aberrant lymph drainage are important when planning surgical treatment and radiotherapy. The aim of this study was to evaluate the intratumoral injection technique in the detection of lymphatic drainage of proved or possibly malignant cold thyroid nodules. The study group consisted of 13 patients with palpable solitary cold thyroid nodules. None of the patients had cystic nodules on ultrasound examination. After fine-needle aspiration biopsy (at least 3 days later), 15 MBq (0.4 mCi) Tc-99m nanocolloid particles in a small volume (0.2 ml) were injected into the nodule. Dynamic images (60 frame x 1 minute) were acquired during the first hour, followed by static anterior and lateral images at 90 and 120 minutes. Radiopharmaceutical was present in the systemic circulation in two patients, possibly as a result of paratumoral injection. Eleven patients had intratumoral accumulation in early frames. Lymph nodes draining the thyroid nodule were visualized in 10 of 11 patients. In the dynamic acquisition period of 7 of 10 patients, the first draining lymph node could also be identified. Only 5 of 13 patients had malignant nodules. Lymphatic metastases were detected in one patient's specimens. Preoperative visualization of lymphatic pathways may be used when planning for thyroid cancer surgery. Sentinel node detection could yield valuable additional information in these patients.