A case of signet-ring cell carcinoma of the gallbladder: immunohistochemistry and differential diagnosis.

The morphological spectrum of gallbladder carcinoma is broad and variable. Most of these tumors are tubular adenocarcinomas. There are some tumors with unusual morphology that may be difficult to classify due to their rarity. One of such tumors is the signet-ring cell carcinoma, which is a highly aggressive, mucin producing variant of gallbladder adenocarcinoma predominantly or exclusively composed of signet-ring cells. Histologically, these tumors are similar to their counterparts in other organs such as stomach, colon and breast, and should not be misinterpreted as metastatic carcinoma from one of these primary sites. The literature about this variant of carcinoma is sparse and little is known about it. We found only three cases of signet-ring cell carcinoma of the gallbladder previously reported. We present the case of an 86-year-old woman with signet-ring cell carcinoma of the gallbladder and discuss the potential diagnostic dilemmas