Incidence of intraglandular lymph nodes within submandibular gland, and involvement by floor of mouth cancer

Resection of the submandibular gland is generally undertaken as an integral component of level I neck dissection for oral cancer. However, it is unclear whether lymph nodes are present within the submandibular gland which may form the basis of lymphatic spread. Our purpose was to investigate the frequency of lymph nodes within the submandibular gland, and the incidence and mechanism of submandibular gland involvement in floor of mouth cancer. Retrospective review of 177 patients with oral cancer undergoing neck dissection. Original pathology slides of floor of mouth cases were re-reviewed by two pathologists to determine frequency of intraglandular lymph nodes, and incidence and mechanism of submandibular gland involvement by cancer. The overall incidence of cervical metastases was 36.4 %, of whom 44 % had level I metastases. Level I metastases were significantly more common in floor of mouth than tongue cancers (p = 0.004). Among 50 patients with floor of mouth cancer undergoing re-review of pathology slides, intraglandular lymph nodes were not found in any of 69 submandibular glands. Submandibular gland involvement by cancer was present in two patients, representing 1 % of all oral cancers, and 4 % FOM cases. Mechanisms of involvement were direct extension, and by an apparent novel mechanism of carcinoma growing along bilateral Wharton’s ducts. Despite the high incidence of level I metastasis in floor of mouth, lymphatic metastases to submandibular gland are unlikely based on absence of intraglandular lymph nodes. We describe a previously unreported mechanism of submandibular gland involvement.