The expression of
desmin, h-
caldesmon,
calponin, CD10, CD34, CD99,
inhibin, and
keratin (AE1/3-Cam 5.2) was studied in 10 conventional
leiomyomas, 9 highly cellular
leiomyomas, 9 epithelioid
smooth muscle tumors, 9
leiomyosarcomas, 10
endometrial stromal tumors (4 with smooth muscle
metaplasia), and 7 uterine
tumors resembling ovarian sex cord
tumors (UTROSCTs). c-kit expression was tested in 10
endometrial stromal tumors, 7 UTROSCTs, and 9
leiomyosarcomas.
Desmin was positive in almost all
smooth muscle tumors except those of epithelioid type, which were positive in only about half of the cases. It also stained areas of smooth muscle differentiation in
endometrial stromal tumors and five of seven UTROSCTs. h-
caldesmon was positive in almost all nonepithelioid
smooth muscle tumors and in areas of smooth muscle differentiation in
endometrial stromal tumors; it was positive in only about half of the epithelioid
smooth muscle tumors and negative in all UTROSCTs.
Calponin was positive in most
tumor types. CD10 was positive in nine of 10
endometrial stromal tumors and five of seven UTROSCTs, although very focally in the latter group. It was also expressed, however, in almost all
leiomyosarcomas, almost 50% of highly cellular
leiomyomas, and rarely in the other
smooth muscle tumors. CD34 was negative in the tested
tumors with rare exceptions. CD99 and
inhibin were positive in four of seven and one of seven UTROSCTs.
Keratin positivity was found in most (five of seven) UTROSCTs and occasionally in
smooth muscle tumors (seven of 37). c-kit was negative in all
endometrial stromal tumors, UTROSCTs, and
leiomyosarcomas. The major conclusions of this study are as follows: 1) Pure
endometrial stromal tumors are usually
desmin negative. 2) In contrast to some previous studies, CD10 expression was often seen in
smooth muscle tumors, including most
leiomyosarcomas and almost half of highly cellular
leiomyomas. As a result, a panel of CD10, h-
caldesmon, and
desmin should be used and will distinguish
endometrial stromal tumors from highly cellular
leiomyomas in most cases. 3) In contrast to a previous study, no significant differences in immunoreactivity were seen between h-
caldesmon and
desmin in
tumors with smooth muscle differentiation. 4) The absence of h-
caldesmon in UTROSCTs helps separate them from epithelioid
smooth muscle tumors. 5) UTROSCTs may express epithelial, stromal, and smooth muscle markers, suggesting divergent differentiation. 6) Our study shows less frequent
inhibin expression in the sex cord-like elements of the UTROSCTs than in other studies. 7) c-kit may help distinguish metastatic
endometrial stromal tumors of the uterus (c-kit negative) from
gastrointestinal stromal tumors (c-kit positive). 8) CD34, CD99, and
keratin have no or minimal role in this area, but
keratin positivity in
smooth muscle tumors should not lead to their
confusion with epithelial
tumors.