Alveolar soft part sarcoma. Assessment of immunohistochemical demonstration of desmin using paraffin sections and frozen sections.

The many different theories on the histogenesis of alveolar soft part sarcoma (ASPS) have caused great confusion. Owing to the recent rapid advance in immunohistochemical studies, two major hypotheses have been proposed. One group of researchers supports the idea that ASPS shows myogenic differentiation, while the other group opposes the idea. This confrontation is essentially one between a group that believes in the immunohistochemically demonstrated presence of desmin in ASPS and a group that denies it. In the present study we detected desmin in 6 of 10 formalin-fixed paraffin sections (although there were differences due to the use of five commercially available types of anti-desmin antibodies). When acetone-fixed paraffin sections and periodate-lysin-paraformaldehyde (PLP)-fixed frozen sections were used in one and three cases, respectively, they were found to be desmin positive, regardless of the type of antibody. The consistent positivity for all anti-desmin antibodies in the cases treated with acetone or PLP is very suggestive of a myogenous origin of ASPS. It is important to take into consideration the fact that formalin-fixed paraffin sections are not very suitable for immunohistochemical study of desmin.