Association of Tumor Metabolic Activity on PET/CT Scan with Pathological Characteristics in Patients with Malignant Melanoma

Background: Melanoma is one of the most serious types of skin cancer and one of the leading causes of cancer-related mortality worldwide. Objectives: This study aimed to investigate the association between 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) scan findings and the pathological characteristics of primary tumors in patients with malignant melanoma. Patients and Methods: In this cross-sectional study, the baseline data of 103 patients with cutaneous or mucosal melanoma (stage III or IV) were recorded, and tumor characteristics and PET/CT scan findings were analyzed. The association between each pathological finding and PET/CT results was also investigated. Results: Patients without a free margin had a significantly higher mean standardized uptake value (SUVmax) of lung metastasis compared to patients with a free margin (3.12 vs. 1.69; P = 0.047). Also, patients with ulceration had a significantly higher mean SUVmax of lung metastasis compared to patients without ulceration (3.28 vs. 1.81; P = 0.041). Based on the results, increased primary tumor thickness was associated with a higher SUVmax of lung metastasis. However, there was no significant association between the metastasis type (single vs. multiple) and free margin, ulceration, or Ki-67 protein. The mean SUVmax of lung metastasis was significantly higher in mucosal melanoma compared to cutaneous melanoma. However, the mean SUVmax values of other metastases (bone, liver, and lymph nodes), even the primary lesion itself, were not significantly different between cutaneous melanoma and mucosal melanoma. Conclusion: The primary tumor margin status, ulceration, tumor thickness, primary tumor location (cutaneous vs. mucosal), and the presence of lung metastasis were significantly associated with PET/CT scan findings.