Objective: The emergence of sentinel lymph node (SLN) technology has provided the ability for an in depth pathologic evaluation for the detection of metastasis to lymph nodes through the use of ultra-staging. The SLN has been shown to be predictive of the metastatic status of its nodal basin. More recently, SLN dissections have been employed in the evaluation of the inguinal lymphatic basins in patients with vulvar malignancies. We hypothesize that the average size of metastasis detected in non-palpable inguinal lymph nodes is smaller when detected through the use of SLN dissection and ultra-staging versus complete inguinal node dissection (CND).
Methods: This was an IRB approved retrospective study. The tumor registry database was searched to identify all patients diagnosed with a vulvar malignancy from 1990 to 2004. The records were reviewed to identify patients with inguinal lymph node metastasis. Only patients with non-palpable inguinal lymph nodes (metastasis 1 cm or less) were included in the analysis. All pathology slides were reviewed. The smallest metastatic foci of cells were measured from lymph nodes obtained through the traditional complete inguinal lymph node dissection (CND) and compared with the largest metastatic foci of cells detected in sentinel lymph node dissections. The mean size and standard deviation for each group was calculated and analyzed with a Mann-Whitney test.
Results: There were 336 inguinal node dissections performed in patients identified with a vulvar malignancy. SLN dissections were performed in 52 groins and CND in 284 groins. Fifty-eight patients were found to have metastatic disease to the inguinal lymph nodes. Thirty of these patients had no evidence of lymph node metastasis on clinical exam or at the time of their EUA. There were 7 groins with metastasis detected through an SLN and 23 groins through a CND. The mean size of the metastatic foci detected in the SLN group was 2.52 mm (SD 1.55) and in the CND group was 4.35 mm (SD 2.63). This was not statistically significant (P = 0.109). However, when comparing the detection of micrometastasis in each set, there was a significant difference (P = 0.02) in the detection of the size of metastasis detected with smaller cluster of cells detected in the SLN group.
Conclusion: SLN dissection with ultra-staging allows for a more extensive pathologic examination of lymph nodes and may allow for the detection of smaller tumor foci than the traditional pathological examination of lymph nodes obtained from a CND. The clinical implication of the detection of these micrometastasis and smaller metastasis remains to be determined.