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Letters to the editor

Dear Editor: We read Metastatic cancer to the floor of mouth: the lingual lymph nodes by Dutton et al with great interest. The case report draws attention to the lingual lymph nodes, which may be of importance for the prognosis of oral cancer. We too are concerned with these nodes and are currently assessing ways to routinely investigate the lymphatic area between tongue tumors and the neck. About a third of patients with squamous cell carcinoma (SSC) of the tongue have clinically evident neck metastases at diagnosis, whereas micrometastases are found in up to 50% of patients with no overt lymph node involvement who undergo neck dissection. Patients with pathologic lymph nodes have a 5-year survival, which is about half that of pN0 cases. Conventional neck dissection removes lymph node levels I–V, or in selective procedures levels I to III or IV. Level I is the submandibular area between the mylohyoid muscle, digastric muscle, and mandibular bone anteriorly, as described by Robbins and does not include the two or three small nodes (maximum size 1 cm) often present in the deep submandibular area, in the proximity of the sublingual gland on the internal surface of mylohyoid muscle, termed sublingual lymph nodes by Rouvière. These nodes are not detected by clinical evaluation or conventional radiologic staging; if metastatically involved, they are rarely increased in size. They are the nodes closest to tongue or floor of the mouth tumors, and hence those most likely to be involved metastatically. Di Nardo also emphasized the importance of these deep submandibular nodes and recommended careful dissection of the internal surface of the mylohyoid muscle. He found involved nodes in this area in 4 of 41 consecutive patients with floor of mouth SCC. En bloc dissection, which requires continuity between the tumor and level I neck nodes, implies removal of the sublingual gland and mylohyoid muscle with associated sublingual nodes. However, these nodes are usually overlooked in the specimen and not examined pathologically. About 10% to 15% of recurrences from tongue cancer develop in the deep tongue or submandibular area, and it is unclear whether these are true recurrences or instead derive from occult metastasis in the sublingual nodes. In a prospective study, Leemans et al compared discontinuous with in-continuity neck dissection for oral cavity carcinomas. They found a 4% recurrence rate in the dissected submandibular area in patients who underwent in-continuity dissection, whereas the discontinuous group did significantly worse, with an overall neck recurrence rate of 19%. For T2–T4 tongue tumors, irrespective of the clinical status of the neck, we prefer en bloc resection of the tumor and lymph nodes. Immediately after excision, the nodal levels and the lymphatic tract between the tumor and the neck including the mylohyoid muscle are marked on the specimen. The tissue between the tumor and level I is sectioned at intervals to check for lymphatic emboli, and, if the presence of sublingual lymph nodes is noted, these are included in the histologic examination. Over the past 15 months we examined this area in 22 new cases of tongue SCC. In five of these we recovered sublingual lymph nodes during en bloc neck dissection, three of them being negative and two metastatic. One of the latter was a T3N2b case with multiple metastases at levels II and III; the other was a T2 tumor with negative neck nodes, with the sublingual lymph node the only involved node. Several centers are evaluating the usefulness of sentinel node biopsy in SSC of the tongue and mouth floor, including ourselves. Our experience is that the presence of radiotracer at the primary injection site, close to the tumor, prevents the sublingual nodes from being revealed by preoperative lymphoscintigraphy, whereas scintigraphy of the resected en bloc Head & Neck 25: 341–342, 2003. Published online 12 February 2003 in Wiley InterScience (www.interscience. wiley.com). DOI: 10.1002/hed.10259