**1.2 Pattern of lymphatic spread**

It is important to understand the pattern of lymphatic spread in DTC as it carries important implications in treatment planning. The prelaryngeal (Delphian) nodes and paratracheal nodes are the most common first sites of nodal metastasis in PTC [7]. Cancer cells then spread laterally to the jugular nodes in a contiguous stepwise fashion prior to spreading to distant sites [8]. If the nodal disease is identified in the lateral neck, both central and lateral neck dissection should be performed. However, "skip metastases", i.e. the presence of lateral nodal disease without central nodal involvement, have been reported in 7–22% of patients with PTC [9, 10]. Multivariate analyses found that skip metastases were most commonly found in patients with unifocal tumor ≤1 cm at the upper one-third of thyroid lobe. Hence, patients without central nodal disease cannot be assumed to be free of lateral nodal metastasis. The knowledge of this pattern of spread enables accurate preoperative assessment of the nodal areas and dictates the necessary extent of neck dissection.
