Malignant Melanoma of Unknown Primary Origin

Abstract

A 37-year-old man was found to have an abnormal shadow on chest X-ray. Chest CT showed a solitary nodule in the right upper lobe. PET/CT showed accumulation in the lung nodule, para-aortic lymph node, left sixth rib, and second lumbar vertebra. A right upper lobectomy was done, and on histology, a malignant melanoma was diagnosed. Though a systemic examination was performed, the original lesion was not detected. He had had lentigo on his back ten years prior which spontaneously regressed three years ago. Thus, an exact diagnosis of the origin skin lesion could not be made Finally this case was diagnosed as a malignant melanoma of unknown primary origin.