Metastatic Urothelial Carcinoma of Occult Primary Origin Revealed by a Necrotic Inguinal Lymph Node: A Rare Case Report

Abstract

Introduction: Occult primary urothelial carcinoma is an extremely rare entity that may present as isolated lymph node involvement without visible bladder or ureteral lesions, making diagnosis particularly challenging.

Case Presentation: We report the case of a 91-year-old man presenting with a left inguinal swelling evolving over four years. Examination revealed a necrotic, fistulized mass with no urothelial lesions on cystoscopy. Biopsy showed a poorly differentiated carcinoma (CK7+/CK20+/p63+/p40+/GATA3−), initially suggesting squamous differentiation, but the lymphatic distribution and suspicious ureteral thickening supported an occult urothelial origin. A multidisciplinary management approach was undertaken. Systemic chemotherapy was not initiated due to age and comorbidities. Local wound care and antibiotic therapy led to partial improvement and clinical stabilization without visceral progression.

Discussion: This case illustrates the diagnostic complexity of dedifferentiated urothelial carcinomas with atypical immunohistochemical profiles. Loss of GATA3 expression, though uncommon, does not exclude urothelial origin, especially in high-grade tumors. Presentation as isolated inguinal lymphadenopathy is exceedingly rare.

Conclusion: Diagnosis of occult urothelial carcinoma requires multidisciplinary collaboration and careful integration of clinical, radiological, and pathological data. In elderly or frail patients, a conservative, symptom-oriented approach is often the most appropriate. Reporting such rare cases is essential to improve understanding of the atypical presentations and dissemination pathways of urothelial carcinoma.