Primary pure signet-ring cell adenocarcinoma of the urinary bladder: a report of three cases with an immunohistochemical study.

Although several case series of primary signet-ring cell adenocarcinoma (SRCA) of the urinary bladder (UB) have been published, primary pure SRCA of the UB composed exclusively of signet-ring cells is rare. In addition, there have been no comprehensive studies of immunohistochemical studies of primary SRCA of the UB. This report shows immunohistochemical profiles of 3 cases of primary SRCA of UB. The age of patients was 37, 43, and 84 years. The male-to-female ratio was 2:1. One specimen was cystectomy, and other two specimens were transurethral bladder tumorectomy. Two patients died of bladder tumor 12 and 16 months after the diagnosis, and one patient is now alive 6 months after the diagnosis. Histologically, all the three tumors were composed exclusively of SRCA cells. Histochemically, all tumors contained neutral and acidic mucins. Immunohistochemically, consistent findings were positive cytokeratin (CK) AE1/3, CK CAM5.2, CK8, CK18, CK19, CK20, p53, Ki-67 (30, 50, 70%), MUC1, and MUC2. CK34BE12, CK5/6, CK14, EMA, p63, vimentin, and MUC6 were consistently negative. CK7 was positive in 1/3, CA19-9 1/3, and MUC5AC 2/3 cases. These data may provide basic knowledge of SRCA of the UB. In conclusion, the author presents three cases of primary pure SRCA with an emphasis of immunohistochemical findings.