Diagnostic value of PB/KOH/PAS method for identification of primary cancer from metastases.

The demonstration of 0-acylated sialic acids in the mucin of cancer metastases by Culling's periodic acid-borohydride-potassium hydroxide-periodic acid-Schiff method (PB/KOH/PAS) is helpful in distinguishing between mucin-producing primary colorectal adenocarcinoma (which will be in 60 to 70% positive) and mucin-producing primary lung adenocarcinoma (which will be negative). In addition to colorectal mucin, the 0-acylated sialic acids may be demonstrated in the mucin of some gastric and gallbladder carcinomas, and only exceptionally in pancreatic, ovarian, and prostatic cancers.