The expression of fine and intermediate filaments in 10 cases of
leiomyosarcoma originating from a large vein, 9 cases of
vascular leiomyoma (
angiomyoma) and one case of a
leiomyoma originating from the wall of the saphena magna vein was studied immunohistochemically by using 6 different anti-
desmin antibodies, one anti-
vimentin antibody and 2
antibodies to muscle-specific
isoforms of actin. All the benign
tumors and all the
leiomyosarcomas of a large vein as well as the vein of origin were positively stained for
desmin. The staining results obtained using the different anti-
desmin antibodies varied considerably, however, and
formaldehyde-fixed tissues were apparently inappropriate for some of them. No single
anti-desmin antibody produced a positivity in all cases, and the extent and distribution of the positivity varied by being irregular and patchy in the
leiomyosarcomas and in the muscle walls of the veins, while the benign
tumors generally revealed a more uniform and strong positivity.
Antibodies to muscle-specific and smooth muscle-specific actin produced a positive staining in all the benign
tumors, as well as all the
leiomyosarcomas and the veins from which they originated. A strong and uniform positivity was observed in the benign
tumors and muscle walls of the veins, while the positivity in the
leiomyosarcomas was more irregular, as it was for
desmin.
Vimentin was constantly expressed in the benign
tumors and in the veins of origin, but only in 5/10 of the
leiomyosarcomas. It is concluded from this study that the immunohistochemical demonstration of
desmin, utilizing a
monoclonal antibody appropriate to the type of fixation used, and muscle specific
isoforms of actin, provide strong support to the light-microscopic diagnosis of
leiomyosarcoma of venous origin.