Initial assessment of positron emission tomography for detection of nonpalpable regional lymphatic metastases in melanoma.

Background: The purpose of this pilot study is to determine the feasibility of positron emission tomography with fluorodeoxyglucose (FDG-PET) for detection of nonpalpable regional lymph node metastases in patients with melanoma.

Methods: Adult patients with histologically proven cutaneous melanoma planned to undergo surgical lymphadenectomy for treatment of nonpalpable subclinical or residual metastatic melanoma in regional lymph node basin(s) participated. Each patient underwent attenuation-corrected PET imaging of the regional lymph node basin(s) with F18 fluorodeoxyglucose (FDG) followed by complete surgical lymphadenectomy. FDG-PET scans were interpreted prospectively by an experienced nuclear medicine physician. FDG-PET scan interpretations and histologic results were then correlated.

Results: Eleven patients underwent 12 FDG-PET scans followed by 12 operations to clear 14 regional lymph node basins. FDG-PET correctly predicted the presence of metastatic melanoma in seven of seven surgical specimens. FDG-PET scans correctly predicted the absence of disease in seven of seven histologically negative node basins. Sensitivity was 1.0; specificity was 1.0.

Conclusions: This study suggests that increased fluorodeoxyglucose uptake in palpably unremarkable regional lymph node basins in patients with melanoma is highly suggestive of metastatic disease.