A103 is a melanocyte-associated
monoclonal antibody that recognizes the
Melan-A/
MART-1 antigen in
melanomas. The
Melan-A/
MART-1 antigen is also expressed in Leydig cells, adrenal tissue, and
steroid-secreting
tumors. A103 immunoreactivity in
ovarian neoplasms, specifically
sex cord stromal tumors (SCSTs), has not been well studied.
Inhibin is known to be expressed in SCSTs but is also expressed in some
carcinomas and other
tumors. We sought to explore the usefulness of both
antibodies in the diagnosis of
ovarian neoplasms. Using conventional tissue sections and a tissue microarray, we studied the immunoreactivities of 131 ovarian
tumors for A103 and
inhibin: 30 SCSTs, including fibrothecoma,
luteoma, hilus cell
tumor, granulosa cell tumor, Sertoli-Leydig cell tumor, and sex cord
tumor with annular tubules, and a control group of 96 surface epithelial
tumors. A few other rare ovarian
tumors including 1
small cell carcinoma, 1
adenocarcinoid tumor, 1 ovarian
tumor of probable wolffian origin, 1
Krukenberg tumor, and 1
desmoplastic small round cell tumor were also studied.
Inhibin staining was generally strong and diffuse in the majority of SCSTs (83%) and at least focally positive in the
small cell carcinoma, ovarian
tumor of probable wolffian origin,
Krukenberg tumor, and
desmoplastic small round cell tumor. Variable immunoreactivities were also present in 7 of 96 (7.3%) surface epithelial
tumors. In comparison, A103 expression was usually weaker and more focal than that of
inhibin and was present in a smaller proportion of SCSTs (37%) and negative in all the surface epithelial
tumors. A103 was typically positive in the
lipid-containing cells (both neoplastic and normal components) of these
tumors (fibrothecomas,
luteomas,
Sertoli-Leydig cell tumors, hilus cell
tumors, and
granulosa cell tumors), and in some cases, moderate positivity was noted in these cells. Weak A103 positivity was identified in the single case of ovarian
tumor of probable wolffian origin. A103 is relatively less sensitive than
inhibin for recognizing SCSTs but does not appear to be expressed by ovarian surface epithelial
tumors. It is therefore more specific than
inhibin for SCSTs and is a useful marker for specifically identifying
lipid-containing cells in
tumors. Thus, adding A103 to a panel of markers including
inhibin may be a valuable adjunct in the differential diagnoses of SCSTs and their distinction from other
ovarian neoplasms.