The lung is an extremely rare primary site for the development of malignant melanoma, in contrast with other tissues where this tumour presents, such as skin, head and neck mucosa, eyes and the gastrointestinal tract. Primary malignant melanoma of the lungs (PMML) is a diagnostic challenge, as clinically and radiologically it cannot be distinguished from the usual primary bronchogenic lung cancer, and its histopathological and immunohistochemical characteristics are little different from those of a lung metastasis from another primary site of malignant melanoma, which is more common. Its diagnosis is based on a number of clinical, radiological and histopathological criteria. In addition, because of its rarity, the knowledge and experience about the prognosis and treatment modalities concerning PMML are inadequate, due to lack of large series. From the little that we know, it appears to be a tumour with poor prognosis, which should be treated by radical surgery, if this is possible, followed by adjuvant chemotherapy and radiotherapy, practically the same as those used for skin melanomas. Metastases to the spleen are an unusual manifestation of malignant melanoma, and may be the cause of continuous high fever.