Evaluation of histochemical methods for the detection of intracytoplasmic mucin in serous effusions

We have studied 25 serous effusions containing definitive morphologic evide nce of adenocarcinoma to evaluate the ability of two mucin stains (Mayer's mucicarmine, D-PAS) to detect intracytoplasmic mucin in both cytologic (cyt ospin) and corresponding histological (cell block) preparations. Mucicarmin e stain was positive in six of 25 (24%) cytospins and 13 of 25 (52%) cell b locks. D-PAS was positive in 19 of 25 (76%) cytospins and 20 of 25 (80%) ce ll blocks. Eight cases were identified which showed mucicarmine positivity in the cell block but not the corresponding cytospin; prolonging incubation time resulted in a positive mucicarmine in cytospin preparations for seven of these cases. We conclude that: (i) D-PAS is a more sensitive stain for the detection of intracytoplasmic mucin in all preparations; (ii) mucicarmi ne shows preferential staining for cell blocks; (iii) alterations in the st aining protocol may permit mucin detection by mucicarmine staining in cytol ogic preparations in a significant number of cases.