Positive Urine Cytology Reveals Melanoma

Rare case links prior melanoma in situ to ureter and porta hepatis metastases

By
Jess Allerton
February 16, 2026
3 min

Conexiant

Objective:

To report a case of metastatic melanoma identified through urine cytology four years after the complete excision of a melanoma in situ lesion.

Approach:

Key Findings:

Metastatic melanoma was confirmed in atypical locations including the ureter and porta hepatis, highlighting the need for careful differential diagnosis.
Urine cytology showed highly atypical cells similar to those in ureteric biopsy, indicating the potential for misdiagnosis.
Immunohistochemical staining supported the diagnosis of metastatic melanoma over urothelial carcinoma.

Interpretation:

The case highlights the potential for melanoma in situ to harbor occult microinvasion, leading to late metastasis, and emphasizes the need for thorough evaluation of atypical genitourinary lesions due to the rarity of such cases.

Limitations:

The rarity of melanoma metastasis to the genitourinary tract complicates diagnosis and may lead to misdiagnosis.
Differential diagnosis may include other malignancies, necessitating comprehensive assessments.

Conclusion:

This case underscores the importance of considering metastatic melanoma in patients with a history of melanoma in situ, integrating clinical history, imaging, and immunophenotyping for accurate diagnosis.