Page 81 - Sentinel lymph node biopsy in oral cavity cancer - Inne J. den Toom

In oral oncology, Gurney et al reported other predictive factors for the presence of non-SLN metastases in SLNB positive necks: tumour site (higher risk as the primary tumour was located at the posterior part of the oral cavity), increased stage (T2-4 stage at higher risk) and number of negative SLNs (lower risk in higher number of negative SLNs).7 In the present study all patients with non-SLN metastases had T2 oral squamous cell carcinoma. Although tumour thickness or depth of invasion and molecular markers have predictive value for the presence of (occult) lymph node metastasis, their role in predicting the presence of non-SLN metastasis in oral cancer patients with a positive SLNB is not known yet.53,54 Our retrospective study suggests if both a positive SLN and a negative SLN are present the prevalence of non-SLN metastases seems nearly equal compared to patients with solely positive SLNs, in contrast to other studies (Table 3). Since distinguishing real SLNs from second echelon nodes may be difficult, it can be anticipated that (some 4 of) these negative SLNs may be in fact second echelon nodes.55 If more positive than negative SLNs are present the probability of non-SLN metastases seems to be higher, also in case of a ratio of positive SLNs of more than 50%. Due to the low number of cases statistical analysis could not be performed and more larger studies are needed to confirm these ideas. A large multicenter study showed in 1/122 neck dissections following positive SLNBs of early oral cancer non-SLN metastases in levels other than I-III.7 These non-SLN metastases had been found in 15% of the patients in the same level, in 17% in an adjacent level and in 2% in a nonadjacent level. In our retrospective study all non-SLN metastases were found in levels I-IV except one in level V. In this latter patient 2 positive SLNs and 5 additional non-SLNs were found. In 67% (4/6) of the patients non-SLNs were only found in nonadjacent levels. If future studies report on the level involved by non-SLN metastases more tailored (super)selective neck dissections may be defined. Analysis of the literature, including our present study, showed that additional non-SLN metastases were found in 31% of neck dissections following positive SLNB. Selected by tumour deposit, these percentages were 13% for ITC, 20% for micro- and 40% for macrometastasis in SLNs. This prevalence may be underestimated since in most studies non-SLNs are examined using routine histopathological examination without step serial sectioning and immunohistochemistry. Studies on neck dissection specimens show that immunohistochemistry can reveal small metastases in 15% of the patients that remain undetected in routine H&E staining.56 79