Pathology of the N0 neck.

The incidence, extent and distribution of nodal metastasis is described in 152 neck dissections from patients with an NO neck undergoing surgery for an intraoral/oropharyngeal squamous cell carcinoma. The preoperative N stage had been determined by palpation under general anaesthesia and magnetic resonance imaging. Metastasis was detected histologically in 32 (21%) of the 152 NO necks. The number of positive nodes per NO neck ranged from 1 to 6. In total, 52 positive nodes were found and 29 (56%) measured 10 mm or less in maximum dimension. Twenty-one dissections (66%) contained a single positive node and 24 (75%) showed a single positive anatomical level. Three cases showed 'skipping' of levels within the neck and one case showed 'peppering'. Seventeen (53%) of the 32 positive NO necks and 31 (60%) of the 52 positive nodes contained only 'micrometastases' (deposits < 3 mm). Microscopic extracapsular spread was evident in five NO necks including one case with extracapsular spread at multiple levels. The study concludes that preoperative staging by palpation and routine magnetic resonance imaging cannot be relied upon to detect early cervical metastatic disease, and the topographic distribution of positive nodes indicates that modified neck dissections should include level IV when the primary tumour involves the tongue.