Expression of SSEA-1 (Lewis^x) on transitional cell carcinoma of the bladder

The expression of stage-specific embryonic antigen 1 (SSEA-1) in transitional cell carcinomas of the bladder (TCCB) has been reported to correlate with tumor grade and the likelihood of lymphatic metastases. We examined the expression of this antigen in TCCBs to evaluate if staining correlated with grade, stage, recurrence, progression and response to intravesical chemotherapy. We studied the expression of SSEA-1 in TCCBs from 74 patients by staining with two different monoclonal antibodies (Mabs), P-12 and anti-SSEA-1, to evaluate if staining correlated with grade, stage and tumor recurrence. Staining was considered as positive or negative irrespective of the intensity of staining. Extent of tumor staining was measured in quartiles of 100% (25, 50, 75 and 100). Follow-up was available in 47/74 (63%) patients and ranged from 6 months to 13 years (median 2 years). Staining with one or both Mabs was observed in 57/75 (76%) tumors. None of the grade I tumors showed > 50% staining while 26% of grade II and only 33% of grade III tumors showed staining of > 50% of cells. 21 % of patients whose tumors showed staining with both Mabs were free of recurrence after resection of the primary tumor; 41% of patients with tumors staining negative with both Mabs showed no recurrence. Expression of SSEA-1 does correlate with tumor recurrence especially in grade II tumors, but the correlation is not very strong (0.05 < p < 0.1). Expression of this antigen is a weak indicator of recurrence in superficial TCCBs.