Unusual Diffuse Ground-Glass Opacities in the Lungs on 18F-FDG PET/CT: A Case of Melanoma With Pulmonary Metastasis.

A 61-year-old man was diagnosed with a malignant melanoma and underwent a resection; he presented with progressive dyspnea after treatment with interferon for 2 months. 18F-FDG PET/CT scan revealed diffuse ground-glass opacities (GGOs) in both lungs with mildly elevated 18F-FDG uptake, similar to that observed with interstitial inflammation. However, a lung biopsy confirmed that the diffuse GGOs were pulmonary metastases of melanoma and were positive for the BRAF mutation. The diffuse GGOs and the progressive dyspnea disappeared after BRAF-targeted therapy. This represents an unusual case of lung metastases from melanoma, mistakenly interpreted as lung inflammation induced by immunotherapy.