Pembrolizumab-Associated Pneumonitis Resembling Lymphangitic Carcinomatosis in a Melanoma Patient

In recent years, many articles have described the adverse events associated with immune checkpoint inhibitors. We report the case of a 63-year-old woman with bilateral lung shadows after 1-year pembrolizumab immunotherapy following surgery for the right-foot melanoma because of positive sentinel lymph nodes. Follow-up F-18-FDG PET/CT demonstrated bilateral diffuse mass-like peribronchovascular opacities with marked FDG uptake. Clinically, melanoma metastases with lymphangitic spread were suspected, and bronchoscopy was performed, although no evidence of malignancy was found. The lung shadow was mostly resolved after steroid treatment. Pembrolizumab-induced pneumonitis can be a mimicker of melanoma metastasis with lymphangitic spread.