A comparison of different methods of detecting mucin in adenocarcinomas of the lung.

The correct classification of carcinoma of the lung is not only of therapeutic and prognostic importance but is also considered to have epidemiological and aetiological significance. Histological tests for mucin are essential in the classification of lung tumours but there is little information available about the influence of the method of detection used on the results of classification. Five established staining techniques were tested using paraffin blocks from surgical specimens of 81 human lung tumours diagnosed as adenocarcinoma, i.e. tumours of WHO Type III. Mowry's alcian blue-periodic acid-Schiff (AB-PAS) technique gave the highest proportion of positives (93%) slightly fewer (90%) being obtained by the PAS technique alone. Both these methods were influenced by the presence of cytoplasmic hyaline globules, structures which cannot be regarded as mucin. The stain recommended by the World Health Organization was also influenced by the presence of hyaline globules, was less frequently positive than the PAS techniques and was considered to have no special advantages. The aldehyde fuchsin-alcian blue sequence was positive in only 83% of cases but provided some information about the type of mucin present. Southgate's mucicarmine also detected mucin in only 83% of cases. It was concluded that the apparent incidence of adenocarcinomas may be influenced by staining methods used. Some standardization of technique is desirable and the AB-PAS combination appears to be the most satisfactory.