Complete response to pembrolizumab in a patient with recurrent and metastatic urothelial bladder carcinoma reflecting coexisting sarcomatoid subtype and glandular differentiation: a case report

Background: In advanced urothelial carcinoma (UC), approximately 20% of patients respond to pembrolizumab, an anti-programmed cell death-1 (PD-1) antibody. Herein, we reported a single case of UC showing coexistence of sarcomatoid subtype and glandular differentiation. Notably, only glandular differentiation was recurrent, probably progressive, and metastatic, which showed complete response to pembrolizumab. Case presentation: An 80-year-old woman presented with hematuria and dysuria, and an intra-vesical tumor was detected on ultrasound. Transurethral resections (TUR) were performed three times. In the first TUR, a sub-pedunculated tumor and a flat lesion were closely but independently located. Pathologically, the sub-pedunculated tumor was an invasive UC, sarcomatoid subtype. Meanwhile, the flat lesion was invasive UC with glandular differentiation. Despite the second and the additional TUR, the tumor was growing and a lymph node metastasis was detected. The third TUR specimen showed UC with glandular differentiation, and a positive PD-L1 expression as well as high density CD8-positive lymphocytic cells infiltration were observed. Pembrolizumab was administered for four courses after terminating the chemotherapy. The CT scan revealed shrinkage of both primary tumor and metastases. Cystectomy and lymph nodes dissection were performed, and no residual carcinoma was detected. The therapeutic effect was regarded as pathological complete response. Conclusions: : Pembrolizumab could be effective for special subtype or divergent differentiation of UC, particularly in an event of an ‘immune hot’ tumor.