American Urological Association - Secondary Tumors
- Secondary malignancy to bladder can either be by direct extension or by metastasis from a distant tumor site.
- Most common sites of origin are colon (21%) (image A), prostate (19%) (image B), rectum (12%), uterine cervix (11%) and melanoma (rare).
- Most secondary bladder tumors are gland-forming (adenocarcinoma); distinction from urothelial carcinoma is difficult when the tumor has a poorly differentiated morphology (no obvious glands).
- Urothelial carcinoma is GATA3+ and uroplakin+ (but has low sensitivity) in contrast to the vast majority of secondary tumors.
- Also urothelial carcinoma is typically CK7+, CK20+, p63+ (nuclear) and high molecular weight keratin (HMWK)+.
- Colorectal adenocarcinoma may resemble bladder adenocarcinoma of enteric morphology (including presence of "dirty" necrosis), and both express the intestinal marker CDX2.
- In contrast to colonic adenocarcinoma, bladder primary adenocarcinoma is nuclear β-catenin- (not all colonic adenocarcinoma though are positive) and often CK7+.
- Poorly differentiated prostate adenocarcinoma that extends into the bladder can be diagnostically challenging.
- In contrast to urothelial carcinoma, prostate carcinoma is PSA+ and PSAP+ (may be negative with poorly differentiated prostate carcinoma!) and is p63- and HMWK-.