Lymph node dissection during sublobar resection: why, when and how?
Appropriate lymph node (LN) assessment is a hallmark of surgical quality of curative intent operations for non-small cell lung cancer (NSCLC). Even in the era of extensive pre-treatment workup including routine PET-scanning and brain imaging, and selective invasive LN evaluation, unexpected LN metastases are found at surgery in more than 10% of patients with a cT1aN0 tumor. Systematic lymphadenectomy minimizes the risk of leaving tumor-LN behind and thus the risk of an incomplete resection, and provides the most truthful pTNM, which is decisive in directing adjuvant chemotherapy. Removal of interlobar, hilar, and mediastinal LNs is necessary during sublobar resection, as it is during lobectomy. In addition, segmental LNs should be dissected at both the resected and nonresected lobar segments, because the lymphatic flow from the resected segment can go directly to the neighboring segmental LNs to join the lymphatic network at the roots of the lobar bronchi, especially for tumors in anteriorly located segments. Finally, several anatomical studies described direct lymphatic vessels from the lower lobes into the upper lobar bronchi LN rendering also advisable clearance of the upper lobar LN in case of lower lobe NSCLC. Given that intralobar LN dissection is impossible within the remaining lobe after wedge resection, omission of segmental and intralobar LN retrieval may also explain the high incidence of loco-regional recurrence observed after wedge resection. Thus, segmentectomy should be preferred to wedge resection as the recommended type of sublobar resection.