In mixed histology bladder cancers treated with standard urothelial therapy, the variant component (e.g., squamous) is hypothesized to be the source of the resistant clone that emerges after treatment. This suggests post-progression biopsies are key to understanding resistance.
Even if a bladder tumor is predominantly a variant histology like squamous, the presence of any urothelial cancer component means it should be treated with the standard urothelial regimen (EV-Pembro). Pure variants without a urothelial element are treated differently.
Plasmacytoid bladder cancer spreads locally along the urothelium, which can be missed on imaging. Clinicians must push for a thorough examination under anesthesia (EUA) before surgery, even if a patient shows a complete radiographic response to therapy.
While getting an expert pathology opinion is valuable for variant histology, it should not delay treatment if a urothelial component is present. Treatment can begin while the detailed review occurs in parallel, as delays can lead to loss of disease control.
Historically, aggressive variants like micropapillary went directly to surgery. However, recent data suggests these patients do poorly due to micrometastatic disease. The trend is now to give neoadjuvant EV-Pembro to treat systemic disease, even with limited specific evidence.
Variant bladder cancers are mostly mixed with urothelial cancer, like rings around a single planet (Saturn). This differs from non-clear cell kidney cancers, which are distinct biological entities, like separate planets. This conceptual model impacts treatment philosophy.