Perimarginal lymph node metastasis in gingivo-buccal complex carcinoma: Is it time to push the limits of neck dissection?.

Abstract

6069 Background: Perimarginal nodes (PMN) are a group of perifacial lymph nodes that lie in close relationship with marginal mandibular nerve (MMN). They lie in the lymphatic drainage pathway of gingivo-buccal cancers (GBC), above the lower border of mandible which forms the superior limit of conventional neck dissection and thus remain unaddressed. With reported incidence of metastasis as high as 20.5%, we aimed to explore incidence of PMN metastasis in GBC, its correlation with histopathological tumor and nodal characteristics. Methods: A prospective study was conducted on 112 consecutive treatment naïve patients of GB squamous cell carcinoma. Patients with unresectable nodal disease, distant metastasis and prior radiotherapy or surgery to neck were excluded. PMN dissection was performed in the quadrangle bounded superiorly by the mandibular alveolar ridge, inferiorly by lower border of mandible, anteriorly by mental foramen and posteriorly by anterior border of masseter. On histopathological analysis, serial step sectioning and cytokeratin immunohistochemistry were performed. Prospective clinical characteristics analyzed were subsite, clinical tumor, nodal stage, location of primary and clinical skin involvement. PMN positivity was correlated with demographic, clinical, nodal status. Histopathological characteristics analyzed included tumor grade, pathological tumor, nodal stage, tumor size, skin and/or bone involvement, depth of invasion, Brandwein Gensler histological risk score and lympho-vascular emboli. MMN functional outcome was graded according to House-Brackman (HB) grading recorded at 3 and 6 months post-operatively. Results: Baseline characteristics are summarized in the table. The PMN were identified histologically in 75.89% (85/112) patients. Metastasis in these nodes were identified in 15.2% (17/112) patients. Our study revealed an occult PMN metastasis of 16.67% (13/78). None of the pre-operative clinical factors was found to be significant in predicting incidence of metastasis. Higher nodal burden (p=0.01) and pathological skin involvement (p=0.03) had statistically significant odds of having PMN metastasis on multivariable analysis. At 6 months follow-up, none of the patients had any MMN functional deformity at rest. Conclusions: There is a high incidence of occult PMN metastasis from gingivo-buccal complex cancer. High nodal stage and pathological skin involvement are independent adverse prognostic factors for PMN metastasis. The limits of conventional neck dissection should be expanded to include clearance of PMN in all cases of gingivo-buccal cancers. [Table: see text]