The large black masses seen in the liver represent metastases of malignant melanoma. The microscopic image demonstrates the epithelioid pattern of melanoma with prominent nucleoli and numerous small brown cytoplasmic melanin granules. The urine has a slight brown color, and upon adding acidified sodium nitroprusside, the urine turns a dark color, here greenish blue. Even more melanin excreted in urine will make the color dark blue, and then black. This phenomenon is uncommon, but melanoma is a neoplasm that can become widely metastatic, and a large amount of tumor making melanin can lead to urinary excretion of melanin.