Immunohistochemical characterization of signet-ring cell carcinomas of the stomach, breast, and colon.

We studied the immunophenotype of signet-ring cell carcinoma (SRCC) of the stomach (30 cases), breast (21 cases), and colon (9 cases) with the following expression patterns: (1) breast: consistent, MUC1 (21 [100%]), cytokeratin (CK) 7 (20 [95%]), estrogen receptor (ER; 17 [81%]); infrequent, E-cadherin (6 [29%]), MUC2, MUC5AC, CK20 (1 [5%] each); negative, CDX2 and hepatocyte paraffin 1 (Hep Par 1; 0 [0%] each); (2) gastric: frequent, CDX2 (27 [90%]) and Hep Par 1 (25 [83%]); variable, E-cadherin and CK20 (17 [57%] each), MUC2 and MUC5AC (15 [50%] each), MUC1 (5 [17%]); negative, ER (0 [0%]); and (3) colon: frequent, MUC2 (9 [100%]), CDX2 and MUC5AC (8 [89%] each); infrequent or negative, MUC1 (3 [33%]), Hep Par 1 (2 [22%]), ER (0 [0%]). Immunohistochemical staining distinguished breast from gastric SRCC (ER, MUC1, Hep Par 1, CDX2) and colon SRCC (ER, CDX2, MUC2, and MUC5AC). Gastric and colon SRCCs showed a similar staining pattern for antibodies tested except for Hep Par 1 and CDX2 (gastric, 83% Hep Par 1 positivity and heterogeneous, weak, patchy CDX2 nuclear staining; colon, 22% Hep Par 1 positivity and homogeneous, strong, diffuse CDX2 nuclear staining). About half of the cases of gastric SRCC expressed MUC2 and MUC5AC, whereas virtually all cases of colon SRCC expressed them.