Mucin-producing tumor of the pancreas.

A new pancreatic tumor, called mucin-producing tumor, has received great attention in Japan. These tumors are found inside the pancreatic duct and produce large quantities of copious mucus. The authors examined 22 cases of these tumors histologically and histochemically. In 12 malignant cases, the tumors inside the ducts consisted of cancerous lesions over small areas along with papillary or atypical hyperplasia. Tumors in ten benign cases mainly consisted of papillary hyperplasia. Except for three patients with carcinoma in situ, cancerous tumors infiltrated the pancreatic parenchyma and, in some cases, were observed invading the bile duct or duodenum. A mucous histochemical study showed evidence of sialomucin in malignant cases; neutral mucin was dominant in benign cases. Characteristics of this disease were also compared with 13 cases of mucinous cystic neoplasm. From the results, it was concluded that these two diseases can be classified into the same conceptual category.