Anatomic-histologic study of the floor of the mouth: the lingual lymph nodes.

Objective: The lingual lymph nodes are inconstant nodes located within the fascial/intermuscular spaces of the floor of the mouth. Oral tongue squamous cell carcinoma has been reported to recur and metastasize in lingual lymph nodes with poor prognosis. Lingual lymph nodes are not currently included in basic tongue squamous cell carcinoma surgery.

Methods: Twenty-one cadavers (7 males, 14 females) were studied, aged from 57 to 94 years (mean age 76.3 years). The gross specimen of the floor of the mouth was divided into blocks: A (median nodes), B, B' (parahyoid), C, C' (paraglandular). Serial histological microslides were cut and stained with hematoxylin-eosin. Frequency of lingual lymph nodes in each block and their microscopic features were assessed.

Results: The lingual lymph nodes in overall number of 7 were detected in 5 of the 21 cadavers (23.8%). The total incidence of lingual lymph node was 33.3% (7 nodes/21 cadavers). Block A failed to demonstrate any lymph nodes (0%); Blocks B, B'-2 nodes (9.5%) and 2 nodes (9.5%), respectively; Blocks C, C'-1 node (4.8%) and 2 nodes (9.5%), respectively. The mean lingual lymph node length was 4.1 mm (from 1.4 to 8.7 mm), the mean thickness was 2.8 mm (from 0.8 to 7.5 mm). Five cadavers (23.8%) revealed mucosa-associated lymphoid tissue. Atrophic changes appeared in 4 (57.1%) lingual lymph nodes.

Conclusion: The presence of lymph node-bearing tissue in the floor of the mouth is demonstrated. In account of resection radicalism and better local control the fat tissue of the floor of the mouth should be removed in conjunction to glossectomy. Further anatomic and clinical research is required to establish the role of lingual lymph node in oral squamous cell carcinoma recurrence and metastasis.