Background: Prognostic assessment for cutaneous melanoma (CM) is based primarily on histological features. The role of 18F-flurodeoxyglucose (18F-FDG) PET is limited to the detection and localization of metastases. Observations of diffuse cutaneous uptake of 18F-FDG in some patients with CM, and subsequent disease progression, warranted further investigation.
Methods: We identified nine patients (mean age 64 years; six men and three women) with CM and diffuse cutaneous uptake of 18F-FDG on PET scans performed between 2006 and 2011.
Results: A review of their medical records revealed that seven patients had rapidly progressive disease and one patient experienced slower disease progression. In the ninth patient, 18F-FDG uptake was attributable to benign lymphoedema. Disease progression manifested as local recurrences at the site of diffuse cutaneous uptake in seven patients; distant metastases were observed in eight patients. Three patients died from melanoma during follow-up at 2, 5 and 18 months following the PET.
Conclusion: Diffuse cutaneous uptake of 18F-FDG was an adverse prognostic marker in these patients. This pattern of uptake may be attributable to the local spread of melanoma cells within the cutaneous lymphatics, leading to inflammation. This cutaneous area may act as a reservoir of melanoma cells. If this is confirmed, the role of PET will be expanded to include the identification of a subset of patients for whom aggressive and targeted management is warranted.