Morphological features of cells containing melanin granules in urine and the identification method

Abstract

Malignant melanoma frequently occurs on the skin, head, and neck, and is known to be one of the tumors with the worst prognosis. It is rare for this cancer to metastasize to the urinary tract and to be detected while the patient is still alive. In this report, we show that the detection of melanoma cells and melanophages in urinary sediment can help detect multiple metastases of malignant melanoma. The patient was a male in his 70s, and a urinalysis during an outpatient visit revealed characteristic atypical cells in the urinary sediment. The atypical cells with a high nuclear-to-cytoplasm ratio, hyperchromasia, enlarged nucleoli, and dark brown melanin granules in the cytoplasm were identified as melanoma cells by various staining methods and immunohistochemical staining. Furthermore, we mentioned the characteristics of melanophages with small and unevenly distributed nuclei and the difference of melanin granules from similar components. Importantly, the number of melanophages in urinary sediment correlated with serum LD and UA levels. In conclusion, melanoma cells and melanophages detected in urinary sediment could be novel markers for malignant melanoma, prognosis prediction, and understanding of the melanoma pathogenesis.