Introduction

It is well known that lymph node metastases are the most important prognostic factor in head and neck cancer. In particular, extracapsular spread (ECS) of positive lymph nodes, which is defined as the penetration of a tumour through the capsule of an involved lymph node, is thought to be a significant adverse prognostic factor. The incidence of lymph node metastases in oral squamous cell carcinoma (OSCC) largely depends on the primary tumour site and increases with the T stage. OSCC located in the tongue and the floor of the mouth have a more obvious propensity for nodal metastasis, and even skip metastasis, compared with OSCC at other subsites. Comprehensive neck dissection (CND; levels I–V), consisting of either radical or modified radical neck dissection, has been a popular approach for the management of cancers of the tongue and the floor of the mouth. CND has been accepted universally for the management of a node-positive neck.

However, accumulating evidence indicates that lymphatic drainage of the oral cavity primarily drains to neck levels I–III. In a recent study on oral cancer, we found that selective supraomohyoid neck dissection (levels I–III) for cN0, and even for the selected cN+ neck, is an appropriate treatment because of its preservation of function and cosmesis without impairing effectiveness. However, in that previous study, the best modality of neck management for pN+ patients with ECS was not discussed.

Of note, cases with macroscopic ECS have a more unfavourable prognosis than those with microscopic ECS. Meanwhile, there is controversy about the prognostic value of microscopic ECS. In this retrospective cohort study, we chose pN+ patients with and without microscopic ECS to evaluate whether patients treated with selective neck dissection (SND; levels I, II, and III, with or without IV) were disadvantaged regarding neck control, complications, and survival compared to patients treated with CND.