Primary signet ring cell carcinoma of gall bladder: report of an extremely rare histological type of primary gall bladder carcinoma.

Signet ring cell carcinoma is an extremely rare type of gall bladder carcinoma composed overwhelmingly (90%) of signet ring cells. It is necessary to exclude a gastric or colonic signet ring cell carcinoma secondarily involving the gall bladder. The primary aim of this case report is to describe the histopathological aspects of this tumour. Primary signet ring cell carcinoma of gall bladder shows dysplastic surface gall bladder epithelium with infiltration of gall bladder wall. It is also necessary to exclude benign signet ring change, which sometimes occurs in the gall bladder. However, it is always confined to the mucosa and does not infiltrate the wall. This case showed grossly diffuse thickening of the gall bladder wall and dysplastic surface epithelium of the gall bladder on histology, with sheets of signet ring cells infiltrating full thickness of the wall. It is also necessary to exclude benign signet ring cell change, which sometimes occurs in the gall bladder. However it is always confined to the mucosa and does not infiltrate the wall.