A histochemical comparison of methylene-blue/acid fuchsin with hematoxylin and eosin for differentiating calcification of stromal tissue

Benign and malignant connective tissue tumors consist of a fibrous component that contains varying amounts of one or more types of bone or other calcified tissue. Diagnosis of these connective tissue tumors often poses challenges for pathologists, because it is difficult to differentiate the organic matrix of osteoid from hyalinized stroma. To establish a definitive diagnosis, it sometimes is advantageous to demonstrate histologically by special staining either the type of calcification or the presence or absence of calcification. We compared the efficacy of methylene blue-acid fuchsin (MB-AF) to hematoxylin and eosin (H-E) for connective tissue tumors suspected to contain calcifications and to devise an optimal staining technique for calcification that would be specific, simple, and cost- and time-effective. We examined 50 benign and 45 malignant connective tissue tumors that were suspected to contain calcifications. Sections were stained with H-E and MB-AF and evaluated. MB-AF stained bone pink, which contrasted with blue soft tissue. After MB-AF staining, osteoid was faint pink in a blue stromal background. Osteoid was not visualized in H-E stained sections; it was stained the same shade of pink as stromal tissue. Dystrophic calcification and cementum could be identified equally well using either staining technique, but contrast was better after H-E staining. MB-AF staining of bone was comparable to H-E staining and could be used effectively to stain bone and osteoid. MB-AF is a simple, single step procedure. It also stains cementum blue with faint blue rimming and dystrophic calcification bluish-pink, but it cannot be used as a specific stain for types of calcification other than bone and osteoid.