Uterine mesenchymal
neoplasms with sex-cord-like elements are designated as
endometrial stromal tumor with sex-cord-like elements (ESTSCLE) or uterine
tumor resembling ovarian sex-cord
tumor (UTROSCT), depending on the extent of sex-cord-like differentiation. Occasionally, sex-cord elements similar to those in ESTSCLE and UTROSCT occur in uterine
adenosarcomas. To determine whether the sex-cord-like elements in these
tumors show immunohistological evidence of sex-cord differentiation, we studied a series of
uterine neoplasms for expression of
inhibin, a peptide hormone expressed by normal ovarian granulosa cells and ovarian sex-cord
neoplasms, and CD99, a
protein also expressed by granulosa cells, Sertoli cells, and some ovarian sex-cord
tumors. Thirty uterine mesenchymal
neoplasms (five epithelioid or plexiform
smooth muscle tumors, three
endometrial stromal tumors, two mixed endometrial stromal and
smooth muscle tumors, 10 ESTSCLE, five UTROSCT, and five miscellaneous stromal processes) and five
epithelial neoplasms were evaluated for expression of CD99 (clone 12E7) and
inhibin (clone R1) in
formalin-fixed,
paraffin-embedded tissue. Three of 10 (30%) ESTSCLE and five of five (100%) UTROSCT were
inhibin and CD99 immunoreactive.
Inhibin staining was confined to the areas with sex-cord-like differentiation, and staining was generally much stronger and more extensive in areas featuring prominent foam cells. There were no differences in the degree or intensity of staining for
inhibin in premenopausal and postmenopausal women. CD99 expression tended to correlate with
inhibin and was typically confined to similar cell types in the individual
neoplasms. Weak CD99 immunoreactivity was seen in one additional epithelioid
smooth muscle tumor, whereas all other mesenchymal and
epithelial neoplasms studied for
inhibin and CD99 were negative. These results provide further immunohistological support for true sex-cord differentiation within uterine mesenchymal proliferations and suggest that the degree of sex-cord differentiation may correlate with the expression of these markers.