Mucins in breast carcinoma.

Mucins produced by breast carcinoma have been shown to be neutral and sialomucins. Colonic mucins were found to be sulfated with an o-acylated sialomucin component that was reported by Culling to be specific to normal colonic epithelium and colonic adenocarcinoma. This type of molecule gives a positive staining after potassium hydroxide/periodate borohydride (KOH/PBT) treatment. We studied the types of mucin in five medullary carcinomas, 10 infiltrating duct carcinomas, and 10 infiltrating lobular carcinomas of the breast. Twenty-two of 25 cases were positive for neutral mucins; 14 of 25 were positive for sialomucin. Sulfated mucins were found in five of 10 cases of infiltrating lobular carcinoma, and in six of 10 cases there was a positive periodic acid-Schiff reaction following KOH/PBT. This study illustrates the presence of sulfated mucin and o-acylated sialomucin in infiltrating lobular carcinoma of the breast. Thus, mucin stains cannot be used in differentiating metastatic breast carcinoma from colonic carcinoma. The significance of this finding and its relation to tumor histogenesis, typing, and biologic behaviors require further analysis.