The role of FDG-PET-CT is limited in initial staging of nodal metastasis for thin cutaneous melanoma

Positron emission tomography computed tomography (PET-CT) is often used to stage nodal metastases in thin cutaneous melanoma, with limited evidence. A retrospective review of patients with cutaneous malignant melanoma treated at our institution was performed from 2005 to 2015, identifying those who received a PET-CT prior to lymphadenectomy. Biopsy features, lymph node status, and PET-CT results were collected. We calculated the overall sensitivity, specificity, accuracy, likelihood ratios, and positive predictive value of PET-CT in identifying nodal metastases. Results were stratified by initial biopsy tumor depth. We identified 367 cases; 95 obtained a PET-CT prior to lymphadenectomy. Overall, sensitivity and specificity of PET-CT was 34.6% and 95.4%, respectively. The positive likelihood ratio and negative likelihood ratio were 7.62 and 0.68, respectively. The accuracy was 78.2%. The positive predictive value for T3 and T4 melanomas were 100% and 81.4%, respectively. For thin melanomas, specificity and accuracy was 88.2% and 88.2%, respectively. PET-CT has low specificity and its use alone is not recommended for initial staging of nodal metastases in thin cutaneous malignant melanoma. •Sensitivity of PET-CT for detection of nodal metastases in all melanomas was 34.6%.•Specificity of PET-CT for detection of nodal metastases in all melanomas was 95.4%.•Calculated positive predictive value of PET-CT in all melanomas was 88.2%.•Specificity of PET-CT for detection of nodal metastases in thin melanomas was 88.2%.•Calculated positive predictive value of PET-CT in thin melanomas was 28.3%. In all melanomas, PET-CT has low sensitivity and accuracy for nodal metastases. In thin melanomas, PET-CT has low specificity and accuracy for nodal metastases.