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Can pathological techniques help identify primary colorectal signet ring cell carcinoma?

May 21, 2008

Primary colorectal signet ring cell carcinoma is a rare but distinctive malignancy of the large bowel. More than 96% of signet ring cell carcinomas arise in the stomach, with the rest arising from other primary organs. Therefore, a secondary infiltration or metastasis to the colon and rectum must be excluded before a definite diagnosis of primary colorectal signet ring cell carcinoma can be established.

This research, performed by a team led by Professor Hsien Lin Sim, is described in an article to be published on April 7, 2008 in the World Journal of Gastroenterology.

The patient presented with a clinical picture of primary rectal signet ring cell carcinoma with peritoneal dissemination and gastric secondaries. Immunohistochemical studies were attempted to differentiate between a gastric and colonic primary. Both specimens were positive for cytokeratins 7 (CK 7) and cytokeratins 20 (CK 20).

Immunostaining profiles for CK 7 and CK 20 have been used to characterize and differentiate signet ring cell carcinoma of breast, stomach and colon. It has been suggested a colon primary is supported if the neoplastic cells have CK 7(-)/CK 20(+) staining pattern, and a gastric primary is supported if they have a CK 7(+)/CK 20(-) staining pattern.

To date, a primary rectal signet ring cell carcinoma with peritoneal dissemination and gastric secondaries had not been described. This case certainly illustrated the aggressive nature of signet ring cell carcinoma. Dr Sim and her colleagues from the Department of Surgery, Alexandra Hospital, proposed that immunohistochemistry may not be 100% accurate in predicting the primary source of signet ring cell carcinoma.

World Journal of Gastroenterology