Signet-ring cell carcinoid of the gallbladder.

A case of signet-ring cell carcinoid of the gallbladder is reported. The tumour diffusely infiltrated the gallbladder wall and extensively ulcerated the mucosa. Neoplastic nests were composed of numerous signet-ring cells mixed with clear endocrine cells. The latter expressed chromogranin A, gastrin and somatostatin and contained neurosecretory granules. The diagnostic problem of differentiating between signet-ring cell carcinomas and composite adenocarcinoma-carcinoid tumours is discussed.