Background
Sentinel lymph node analysis is the standard of care in malignant melanoma treatment. Complete lymphadenectomy is recommended if the sentinel node shows metastasis. Frozen section assessment of the sentinel nodes has been shown to be unreliable. Permanent section pathology take 3-5 days before results are received. We undertook this study to evaluate the feasibility of using a rapid immunohistological stain to interoperatively identify lymph node metastasis.
Twenty-five patients with malignant melanoma (depth greater than 1mm) were enrolled under an IRB approved protocol. Sentinel lymph nodes were identified and biopsied by standard surgical techniques. The nodes were cut in 2mm sections, two pairs of touch preps were made with each section and immunostained with MCW cocktail. The nodes were processed with standard H & E stain and immunostaining with MCW cocktail. After protocol completion(25 patients), results of the rapid slides were compared to the conventional stains and permanent immunostains.
Results
The turnaround time for processing the rapid slide was 28 (24-37) minutes. 17%(8 of 48) of the lymph nodes in 28% (7 of 25) cases were positive. All micrometastasis, except 1 node, were identified with the rapid slide. Sensitivity of the rapid slide was 86%, specificity was 100%, negative predictive value was 95%, and positive predictive value was 100%.
Conclusion
Micrometastasis can be reliably detected intraoperatively with the MCW cocktail rapid immunostain. We are currently performing definitive complete lymphadenectomy at the same surgical setting as sentinel node biopsy and wide excision.