Squamous cell carcinoma of the floor of the mouth: tumour thickness and the rate of cervical metastasis.

BACKGROUND: Increased thickness of oral cavity squamous cell carcinoma (SCC) has been shown to be associated with higher rates of cervical metastasis. Most of the previous studies have focused on SCC of the oral tongue. There are few studies that have examined solely carcinoma of the floor of the mouth and these studies differ in the thickness of tumour that is associated with significantly increased rates of cervical metastasis.
METHODS: Patients with SCC of the floor of the mouth of all stages who were treated with excision and neck dissection were identified. Primary tumour thickness and other pathological features were determined in the pathological specimens and were correlated to the incidence of pathological cervical lymph node metastasis. Fisher's exact test and the unpaired t-test were used for statistical analysis.
RESULTS: Fifty-three patients were studied (43 men and 10 women). The median age was 56.5 years (range 43-86 years). The median tumour thickness in patients with lymph node metastases (14.6 mm) differed significantly from those without metastases (8.6 mm) (P = 0.004). When T1 and T2 cases were looked at in isolation, the median tumour thickness of cases with lymph node metastases (11.1 mm) again was significantly greater than those without metastases (4.6 mm) (P = 0.04). Subgrouping tumours into those > or =7.5 mm or < 7.5 mm showed a significantly increased rate of lymph node metastasis (57% compared with 12%, P = 0.001). There was no statistically significant association between perineural invasion or tumour differentiation and the presence of lymph node metastases.
CONCLUSION: Tumour thickness has been shown to be directly related to rates of cervical lymph node metastasis in floor of mouth SCC. The primary tumour thickness associated with significantly increased rates of metastasis is similar to that shown in previous studies examining SCC of the oral tongue.