Significance of pigmented urothelial and non-urothelial cells in voided urine specimens: A case report and review

We present a case of metastatic malignant melanoma to the urinary bladder diagnosed on a voided urinary cytology specimen in a patient who visited the emergency department complaining of right flank pain, and dark urine. The patient reported having previous episodes of kidney stones. Additionally, more detailed clinical history obtained after the cytological diagnosis, revealed a previous excision of malignant melanoma on the back 10 years ago. The diagnosis of metastatic malignant melanoma was based solely on voided urine cytology. While metastases of malignant melanoma to urinary bladder are well known, the significance of pigmented cells in voided urine specimens is not well documented. In this article we provide a discussion as well as a review of the literature about possible disease entities associated with pigment containing urothelial as well as non-urothelial cells.