Koos Boeve

89 Lymphatic drainage patterns of oral maxillary tumors INTRODUCTION Carcinomas of the oral cavity metastasize predominantly by the route of the lymphatic vessels to the lymph nodes in the neck. Removal of the lymph nodes by neck dissection is an important part of the treatment of oral cavity cancer and improves disease outcome [1]. The risk of having metastasis from oral squamous cell carcinoma (OSCC) is influenced by tumor characteristics such as localization, infiltration depth and stage [2,3]. Each region of the oral cavity has a specific lymphatic drainage pattern that is used by surgeons to plan the patient specific treatment [4]. Oral maxillary cancer is relatively rare compared with other anatomic subsites of oral cavity cancer (e.g. tongue and floor of mouth) and is rarely included in studies on oral lymphatic drainage patterns [4-6]. Lack of evidence on the lymphatic drainage patterns of oral maxillary cancer has led to a variety of guidelines on the treatment of the clinical negative (cN0) neck; watchful waiting, elective neck dissection (END) or radiotherapy. ENDs are recommended if the probability of a lymph node metastasis exceeds 20% [7]. Traditionally, neck dissections were reported to be uncommon in oral maxillary cancer, which has been based on a low regional failure rate in a few studies with different definitions of oral maxillary cancer from the previous century [8,9]. Another reason for restraining neck dissections were a few reports about parapharyngeal regional failure in a study with oral maxillary and sinus maxillary cancer [10]. Surgical treatment of the parapharyngeal space is technically challenging and mostly radiotherapy is given. More recent studies have investigated maxillary OSCC specifically and found a regional lymph node metastasis rate at least as high as other regions of the oral cavity, especially in the cervical lymph nodes; overall incidence range regional failure 14 -38% [11-18]. Because of these new insights in regional metastases rates, several authors recommend an END in case of cT3-4N0 tumors and also to consider an END in cT1-2N0 maxillary OSCC [11-14,16-19]. Because ENDs are indicated in maxillary OSCC, these patients might possibly benefit from a sentinel lymph node biopsy (SLNB), which is accepted as a minimal invasive alternative for an END in early stage oral cavity cancer [20]. However, as far as we know, no literature is available for the location of the sentinel lymph node in maxillary OSCC. Better insight into the lymphatic drainage pattern, especially in the location of the sentinel lymph node, is needed to make a clear decision in treatment of the cN0 neck in maxillary OSCC [18]. We hypothesized that the sentinel lymph node in patients with maxillary OSCC is located at cervical levels because retrospective studies have shown that late metastasis of maxillary OSCC occur in these cervical levels. The purpose of this study was to identify the lymphatic drainage pattern of oral maxillary cancers via preoperative lymphoscintigraphy which was executed as part of the SLNB procedure.