Pulmonary blastoma with malignant melanoma component. Pulmonary blastomas are rare primary tumors that consist of tubular or glandular structures embedded in an undifferentiated mesenchymal stroma. Focal cartilage, bone, and skeletal muscle as well as squamous differentiation have been described in these tumors. We report a unique case of a pulmonary blastoma showing a malignant melanoma component. Immunohistochemical stains for S100 protein and HMB-45 were positive in the areas of melanocytic differentiation. 