Case report: differential diagnosis of isolated iliac lymphadenopathy following Bacillus Calmette-Guérin treatment for high-risk superficial bladder cancer.

We report the unusual case of a patient with G3 pT1 transitional cell carcinoma (TCC) of the bladder, which was treated with repeated transurethral resection and maintenance intravesical Bacillus Calmette-Guérin (BCG) therapy. At 30 months follow-up, a symptomatic, solitary iliac lymph node mass was identified and biopsied. Histology demonstrated granulomatous tissue only, in the absence of any intravesical bladder tumour recurrence. Following 6 months of anti-tuberculous medication, the mass had progressed, and repeat biopsy revealed undifferentiated carcinoma (of a bladder primary). This is a rare case of metastatic superficial bladder cancer progression without local recurrence after BCG therapy. As such, it can be viewed as a diagnostic challenge.