From the Guidelines
The most common site for papillary thyroid carcinoma (PTC) metastasis is the regional cervical lymph nodes, particularly those in the central neck compartment (level VI). Approximately 30-80% of PTC patients will have lymph node metastases at diagnosis, with the central neck compartment being involved first, followed by the lateral neck compartments (levels II-V) 1. This lymphatic spread pattern is due to the rich lymphatic drainage of the thyroid gland and the tendency of PTC to spread via lymphatic channels before hematogenous dissemination. Some key points to consider in the management of PTC include:
- The use of thyroid and neck ultrasound to evaluate the central and lateral compartments, as recommended in the NCCN guidelines 1
- The consideration of CT/MRI with contrast for fixed, bulky, or substernal lesions, as well as the evaluation of vocal cord mobility in patients with abnormal voice or surgical history involving the recurrent laryngeal or vagus nerves 1
- The importance of prophylactic central neck dissection in some PTC cases, particularly those with clinically apparent or biopsy-proven disease 1
- The role of molecular testing for DTC, including diagnostic, prognostic, and predictive purposes, as discussed in the NCCN guidelines 1 Distant metastases are uncommon in PTC (occurring in only 1-15% of cases) but when they do occur, the lungs and bones are the most frequent sites. The propensity for lymphatic spread underlies the rationale for performing prophylactic central neck dissection in some PTC cases and explains why ultrasound evaluation of cervical lymph nodes is a critical component of preoperative assessment and postoperative surveillance for these patients.
From the Research
Most Common Site for PTC Metastasis
- The most common site for papillary thyroid cancer (PTC) metastasis is the cervical lymph nodes, with a frequency of 30% to 90% of patients 2.
- Cervical lymph node metastases in PTC usually spread in a contiguous fashion, but "skip metastasis" to lateral lymph nodes without central lymph node metastasis can also occur 3.
- The frequency of lymph node metastases in PTC is higher in the central compartment, but lateral lymph node dissection may be necessary in some cases, especially if preoperative ultrasonography or computed tomography suggests lateral node metastasis 3.
- The central lymph nodes are the most common site for PTC metastasis, and level VI lymph node dissection may be recommended for patients with PTC 4.
- Retropharyngeal lymph node metastasis is extremely rare in PTC, but can occur, and may require additional surgical treatment 5.
- The patterns of cervical lymph node metastasis in PTC can be influenced by factors such as younger age, larger tumor size, multiplicity, bilaterality, encapsulation, extrathyroid extension, and lymphatic invasion 3.