Clinical impact of iodine staining for diagnosis of carcinoma in situ in the floor of mouth, and decision of adequate surgical margin.

OBJECTIVE: The use of iodine staining has been recommended for the early detection of squamous cell carcinoma (SCC) in the upper aerodigestive tract. The purpose was to verify the effectiveness of iodine staining in detecting early squamous cell carcinoma in the floor of mouth.
METHODS: Between 1995 and 2005, otolaryngological examinations including the floor of mouth were performed for 2278 esophageal cancer patients as a screening program of high-risk patient group. Iodine staining was applied to a lightly reddish and/or white patch, and/or uneven lesions in the floor of the mouth. Forceps biopsy was performed for demarcated unstained or lightly stained lesions. Three patients with the tumors in the floor of mouth, which were diagnosed as more over T2 level just by visual examination, were excluded from this study. If SCC was found in the specimen, mucosal resection was performed with a safety margin of 2mm from the unstained or lightly stained lesion. The incidence, rate of carcinoma in situ, and prognosis of cancer of the floor of mouth (CFOM) were assessed.
RESULTS: Iodine staining was performed for 72 of 2278 patients (3.2%) according to the presence of suspicious reddish and/or whitish and/or uneven lesions. Of these, unstained or lightly stained areas after iodine staining were recognized in 47 patients and SCC was revealed in 28 of 47 patients. The diagnosis of other 19 patients included inflammatory mucosa (n=11), low grade dysplasia (n=6), and hyperkeratosis (n=2). Sensitivity and specificity of iodine staining for detecting SCC were 100% and 59.6%, respectively. Pathological diagnosis of the 28 patients included squamous cell carcinoma in situ (n=12), microinvasive squamous cell carcinoma (n=15) disease, and focal invasive squamous cell cancer (n=1). Twenty-four of 28 patients were treated with mucosal resection without mandible resection. The other 4 patients did not receive the treatment of CFOM due to concomitant far advanced esophageal cancer. In 24 patients undergoing mucosal resection, no patients developed local recurrence or metastasis to the cervical lymph nodes during an average of 74.2 months of follow-up period (from 7 to 156 months). The 5-year cause-specific survival of these patients was 100%.
CONCLUSION: The use of iodine staining as a part of otolaryngological examinations may be beneficial for the early detection of CFOM, including carcinoma in situ and micro-invasive SCC. Moreover, it would be very useful to determine an adequate surgical margin for locally mucosal resection.