Kidney Week

Abstract: SA-PO1028

Melanuria: Black Urine as a Presenting Sign of Metastatic Melanoma

Session Information

• Pathology and Lab Medicine - II
  November 04, 2023 | Location: Exhibit Hall, Pennsylvania Convention Center
  Abstract Time: 10:00 AM - 12:00 PM

Category: Pathology and Lab Medicine

• 1800 Pathology and Lab Medicine

Authors

• Nogueira De Sa, Patricia, University of Pennsylvania, Philadelphia, Pennsylvania, United States

Patricia Nogueira De Sa,

• Zariat, Asheen, University of Pennsylvania, Philadelphia, Pennsylvania, United States

Asheen Zariat,

• Shulman, Rachel, University of Pennsylvania, Philadelphia, Pennsylvania, United States

Rachel Shulman,

• Leonberg-Yoo, Amanda K., University of Pennsylvania, Philadelphia, Pennsylvania, United States

Amanda K. Leonberg-Yoo,

Introduction

The worldwide incidence of malignant melanoma has been increasing at an average annual rate of 5%.¹We describe a case of melanuria as an initial sign of metastatic melanoma in a previously healthy young woman.

Case Description

A 24-year-old female with no medical history presented with two weeks of abdominal pain.On admission, she had mild tachycardia. Physical exam was notable for abdominal tenderness and lower extremity edema.Blood work showed creatinine of 1.5 mg/dL,lactate 19mmol/L,LDH 5000 IU/L.Amber urine that turned black upon exposure to air.Urine studies were negative for hemoglobin and bilirubin and microscopy showed dark brown casts and atypical cells with dense inclusions exhibiting a dark rim.Abdominal CT showed multiple hepatic and splenic lesions,suspicious for neoplasm.Liver biopsy showed BRAF-negative metastatic melanoma.Despite treatment,the patient expired on hospital day 13^th.

Discussion

Melanuria is the urinary excretion of melanin precursors leading to black discoloration of the urine.It is present in up to 15% of cases of malignant melanoma and typically occurs with diffuse melanosis.^2,3Urine sediment may show atypical pigment-laden cells and dark brown casts.Our patient had dark casts with atypical cells suggesting melanin-containing tubular epithelial cells and histiocytes.Although we did not test her urine for melanin precursors,we proposed the melanuria resulted from extensive tumor necrosis causing cytolysis of melanocytes and subsequent excretion in the urine.This case demonstrates that metastatic melanoma should be considered in the differential diagnosis of black urine.