Perimarginal quadrangle dissection: Pushing the boundaries of neck dissection in gingivo-buccal complex cancer.

ABSTRACT

OBJECTIVES: Perimarginal nodes (PMN) lie in close relationship with marginal mandibular nerve (MMN), in the lymphatic drainage pathway of gingivo-buccal cancers (GBC), above the lower border of mandible and remain unaddressed in conventional neck dissection. We have aimed to define the boundaries of perimarginal node dissection, explore incidence of PMN metastasis and its correlation with histopathological characteristics. MATERIALS AND METHODS: A prospective study was conducted on 112 consecutive patients of GB carcinoma. PMN dissection was performed in an anatomically defined quadrangle. Prospective clinical characteristics included subsite, tumor and nodal stage, location of primary and clinical skin involvement. Histopathological characteristics analyzed included grade, size, pathological tumor, nodal stage, skin and/or bone involvement, depth of invasion, Brandwein Gensler histological risk score and lympho-vascular emboli. MMN function was graded at 3 and 6 months post-operatively. RESULTS: The PMN were identified histologically in 75.89 % patients. 15.2 % patients harboured metastasis in PMN. 16.7 % patients had clinically occult metastasis with 11.7 % having isolated PMN metastasis. 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) were found statistically significant on multivariable analysis. At 6 months follow-up, none of the patients had any MMN functional deformity at rest. CONCLUSION: There is a high incidence of occult PMN metastasis from gingivo-buccal complex cancer. High nodal stage and pathological skin involvement are independent predictors for PMN metastasis. PMN dissection must be performed in all cases of GB cancer.