Inhibin and CD99 (MIC2) expression in uterine stromal neoplasms with sex-cord-like elements

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.

Relaxin-like factor (RLF): a new specific marker for Leydig cells in the ovary

Relaxin-like factor (RLF), also known as the Leydig cell insulin-like factor (Ley-I-L), is a novel member of the insulin-IGF-relaxin family of hormones and growth factors that has recently been shown to be strongly expressed in testicular Leydig cells. Expression of the RLF peptide in the human ovary and in ovarian tumors has not been studied. In the present study, the expression of the RLF peptide in the human ovary was investigated by immunohistochemistry using a specific antibody raised against human RLF. By this method, RLF was found to be expressed in hilus (Leydig) cells and theca interna cells but absent in granulosa cells, ovarian stromal cells, and surface epithelium. RLF expression was also observed in the corpus luteum, although at a lower level than in theca cells. Thirty-seven sex cord-stromal tumors and five cases of hilar Leydig cell hyperplasia were also investigated for RLF expression. RLF was found to be strongly expressed in hilar Leydig cell hyperplasia and sex cord-stromal tumors with a component of Leydig or luteinized cells. Of the analyzed theca cell tumors, two displayed a diffuse staining pattern. As expected, RLF was not expressed in granulosa cell tumors. In conclusion, RLF appears to be a useful marker for Leydig cells in the human ovary and may be a diagnostic supplement in hyperplasias and tumors derived therefrom.

Ki-A10, a germ cell nuclear antigen retained in a subset of germ cell-derived tumors

Monoclonal antibody Ki-A10 recognizes a nuclear antigen of 25 and 22 kd apparent molecular mass, which is abundantly expressed by immature gonocytes, spermatogonia, and spermatocytes, whereas it is absent in spermatids, spermatozoa, oocytes, and normal somatic tissues. In a broad spectrum of human cancers the antibody showed no reactivity except for a small subset of malignant lymphomas. Because of this restricted expression pattern, we examined 173 germ cell tumors and 18 sex cord stromal tumors immunohistochemically to assess the distribution of the Ki-A10 antigen. A strongly positive reaction was found in classic seminomas, dysgerminomas, spermatocytic seminomas, and the germ cell component of gonadoblastomas. Yolk sac tumors presented a heterogeneous reactivity pattern ranging from overall positivity to complete lack of antigen expression, and in three of eight choriocarcinomas, a few clusters of cytotrophoblast cells were strongly labeled. All other tumors, including Leydig and Sertoli cell tumors as well as placental tissue, were negative. Our findings suggest that specific germ cell antigens can be retained in germ cell tumors along particular differentiation pathways. Ki-A10 is the first marker that consistently labels spermatocytic seminoma, further confirming its germ cell origin and suggesting a close relationship to classic seminoma. The antibody may serve for diagnostic purposes and promises new insights into the process of germ cell differentiation and the development of germ cell-derived neoplasia.

Endometrial stromal nodule with retiform sex-cord-like differentiation

We describe an interesting case of uterine stromal nodule with sex-cord-like differentiation of retiform type. The tumour occurred in a 51-year-old woman. It contained areas of retiform patterns mimicking an epithelial component of some of mullerian biphasic tumours. Areas of classical sex-cord-like and smooth muscle differentiations were also found. The sex-cord-like cells revealed a smooth muscle phenotype in ultrastructural and immunohistochemical studies.

Inhibin A is a sensitive and specific marker for testicular sex cord-stromal tumors

We compared the expression of inhibin A, chromogranin, synaptophysin, S-100 protein, cytokeratins AE1/AE3, 7, and 20, and estrogen and progesterone receptors in testicular sex cord-stromal tumors: 11 Sertoli cell tumors, 3 Sertoli cell adenomas (nodules), 26 benign Leydig cell tumors, 7 malignant Leydig cell tumors (defined clinically by metastatic behavior), and a variety of germ cell tumors. Inhibin was the most sensitive marker, expressed in 91% of the Sertoli cell tumors and 100% of the Sertoli cell adenomas and Leydig cell tumors. The non-neoplastic Sertoli and Leydig cells invariably stained for inhibin. Conversely, no germ cell tumors were immunoreactive. One testicular tumor of the adrenogenital syndrome was immunoreactive. Neuroendocrine marker immunoreactivity was variable. Chromogranin was expressed in the non-neoplastic Sertoli and Leydig cells, 82% of the Sertoli cell tumors, 92% of the benign Leydig cell tumors, and 43% of the malignant Leydig cell tumors. Synaptophysin was expressed in the non-neoplastic Sertoli and Leydig cells, 45% of the Sertoll cell tumors, and 70% of the Leydig cell tumors, in approximately similar proportions between the benign and malignant Leydig cell tumors. S-100 protein was expressed in 64% of the Sertoli cell tumors, 8% of the benign Leydig cell tumors, and none of the malignant Leydig cell tumors. Cytokeratins AE1/AE3 were expressed in 64% of the Sertoli cell tumors and 42% of the Leydig cell tumors, with similar proportions in the benign and malignant cases. Estrogen and progesterone receptor expression were identified in 24 and 39% of benign and malignant Leydig cell tumors, respectively. We conclude that inhibin is a characteristic marker for Sertoli and Leydig cells and that it serves to differentiate testicular sex cord-stromal tumors from germ cell tumors.

CD99, keratin, and vimentin staining of sex cord-stromal tumors, normal ovary, and testis

CD99, a marker for MIC-2, reacts with normal Sertoli cells and granulosa cells. We investigated CD99 expression in the development of normal ovary and testis as well as in 25 sex cord-stromal tumors (SCSTs), 7 epithelial neoplasms, and 6 germ cell tumors. Normal Sertoli cells and mature granulosa cells showed 3+ staining with CD99. Pregranulosa cells of primordial follicles were negative. All of the eight Sertoli-Leydig cell tumors were positive with antibody to CD99, with the well-differentiated tumors showing the greatest degree of staining intensity. Reactivity of 2+ to 3+ with CD99 was observed in all of the 11 granulosa cell tumors and in yolk sac components of the germ cell tumors investigated. All of the poorly differentiated carcinomas were negative with CD99. We concluded that CD99 might be a useful marker for SCSTs and that its degree of reactivity correlates with the degree of differentiation in Sertoli-Leydig cell tumors. Additionally, CD99 might aid in distinguishing granulosa cell tumors of the ovary from poorly differentiated carcinomas.

Müllerian inhibiting substance, alpha-inhibin, and CD99 expression in sex cord-stromal tumors and endometrioid ovarian carcinomas resembling sex cord-stromal tumors

Müllerian inhibiting substance (MIS), alpha-inhibin, and CD99 are expressed by normal and neoplastic sex cord and stromal gonadal derivatives. The expression of MIS, inhibin, and CD99 was evaluated by immunohistochemistry in a series of 19 sex cord-stromal tumors and seven ovarian endometrioid carcinomas resembling sex cord-stromal tumors. Normal ovaries and testes from patients with the androgen insensitivity syndrome were used as control. All three markers were detected in primordial ovarian follicles and immature seminiferous tubules. Both inhibin and MIS were expressed by all sex cord-stromal tumors, but inhibin immunostaining appeared stronger and more diffusely distributed. CD99 was expressed by all adult and juvenile granulosa cell tumors, but only focally by Sertoli-Leydig cell tumors. In Sertoli-Leydig cell tumors, the three markers were predominantly expressed by the Sertoli cells. None of the seven endometrioid carcinomas with a sex cord-stromal pattern was positive for MIS or inhibin; two of them reacted for CD99, but their staining patterns were not membranous. Inhibin immunoreactivity was also detected in foci of stromal luteinization, occasionally present in these tumors. MIS, inhibin, and CD99 are potentially useful markers in the differential diagnosis between sex cord-stromal tumors and endometrioid carcinomas resembling sex cord-stromal tumors.

Inhibin expression in ovarian tumors and tumor-like lesions: an immunohistochemical study

We investigated 203 ovarian tumors and tumor-like lesions for inhibin expression using a monoclonal anti-inhibin alpha antibody. Inhibin was present in the tumor cells in all 14 primary adult granulosa cell tumors (4 luteinized) plus 3 metastatic, all 10 primary juvenile granulosa cell tumors plus 1 metastatic, 10 of 11 thecomas, 3 of 11 fibromas, 4 of 11 sclerosing stromal tumors, 6 of 11 Sertoli cell tumors (1 oxyphilic), 7 of 11 Sertoli-Leydig cell tumors, 1 gynandroblastoma, 10 primary ovarian sex cord tumors with annular tubules plus 2 metastatic, 8 of 9 steroid cell tumors, both pregnancy luteomas, 1 of 2 unclassified sex cord tumors, 2 of 5 gonadoblastomas, 9 of 10 female adnexal tumors of probable wolffian origin, and in the non-neoplastic stroma of many carcinomas and germ cell tumors. The tumor cells were inhibin-negative in 10 fibrosarcomas, 12 small cell carcinomas of hypercalcemic type, 24 germ cell tumors (except for a focus of inhibin-positive syncytiotrophoblast in one case), and 17 ovarian carcinomas. Two of the three inhibin-positive fibromas showed diffuse immunostaining and were associated with evidence of estrogenic activity. Among nine Sertoli-Leydig cell tumors with available clinical data, four that were more than minimally inhibin-positive were accompanied by androgenic manifestations; five inhibin-negative or only minimally positive tumors lacked such evidence. Inhibin immunostaining may be useful in the differential diagnosis of inhibin-positive sex cord tumors versus histologically similar inhibin-negative neoplasms, but inhibin negativity does not preclude a diagnosis of sex cord tumor. The unexpected, common inhibin positivity of female adnexal tumors of probable wolffian origin indicates that inhibin staining cannot be used to differentiate these tumors from Sertoli cell tumors. Inhibin immunostaining is also helpful in identifying potential steroid hormone-secreting cells in the non-neoplastic stromal component of epithelial, germ cell, and other ovarian tumors.

Ovarian endometrioid carcinomas simulating sex cord-stromal tumors: a study using inhibin and cytokeratin 7

We have investigated the use of inhibin and cytokeratin-7 (CK-7) in distinguishing endometrioid ovarian carcinomas (both typical and sex cord-like) form granulosa cell and Sertoli cell-containing ovarian tumors. Immunohistochemical staining with inhibin, CK-7, and epithelial membrane antigen (EMA) was performed on 6 endometrioid carcinomas simulating sex cord-stromal tumors, 5 typical endometrioid carcinomas, 14 adult granulosa cell tumors (AGCTs), 3 Sertoli-Leydig cell tumors (SCLTs), and 1 sex cord tumor with annular tubules (SCTAT). All AGCTs and SLCTs as well as the SCTAT were inhibin-positive. In contrast, all of the endometrioid carcinomas (both typical and those mimicking sex cord-stromal tumors) were inhibin-negative. CK-7 expression was not observed in the granulosa cell tumors and it was noted only in retiform areas in SLCTs. All 5 typical endometrioid carcinomas and 5 of the 6 sex cord-like endometrioid carcinomas were CK-7 positive. EMA was positive in all carcinomas but negative in the SCTAT, AGCTs, and SLCTs. Inhibin can distinguish between sex cord-stromal tumors (whether granulosa or Sertoli-Leydig type) and endometrioid carcinomas. CK-7 is also helpful in differentiating between AGCTs and most endometrioid carcinomas, and may also aid in separating SLCTs from sertoliform carcinomas. The addition of inhibin to an antibody panel is important because it provides a positively-staining marker for sex cord-derived cells.

Hormonally active ovarian tumors

Steroid-hormone-producing ovarian tumors include those in which the neoplastic cells secrete hormones as well as a wide variety of tumors in which the neoplastic cells stimulate the ovarian stroma or adjacent hilus cells to become hormonally active.

Stimulation of activin receptor II signaling pathways inhibits differentiation of multiple gastric epithelial lineages

Activins are TGFbeta family members known to mediate a variety of developmental events. We examined the effects of activins on the self-renewing epithelial lineages present in gastric units of the adult mouse stomach. These lineages are descended from multipotent stem cells located in the midportion of each unit. The stem cell and its immediate descendants can be identified by their morphological features. Studies of knockout mice lacking activins A or B, and/or activin type II receptors (ActRII) revealed that ActRII-mediated signaling is not required for normal gastric epithelial morphogenesis or homeostasis. Mice homozygous for a null allele of the alpha-inhibin gene (inha[m1/m1]) develop gonadal sex cord stromal tumors that secrete large amounts of activins A and B. Analysis of inha(m1/m1) mice, with or without gonads, established that supraphysiological levels of activins block differentiation of preparietal to acid-producing parietal cells, differentiation of neck cells to pepsinogen-producing zymogenic cells, and terminal differentiation of mucus-producing pit cells. ActRII mRNA is normally present in pit, parietal, and zymogenic cells. inha(m1/m1)actRII(m1/m1) compound homozygotes develop activin-secreting gonadal tumors but have no abnormalities in their gastric epithelium, indicating that persistent stimulation of ActRII-dependent signaling pathways produces pleiotrophic effects on gastric epithelial differentiation. When a lineage-specific promoter is used to ablate mature parietal cells with an attenuated diphtheria toxin A fragment in transgenic mice, there is increased proliferation of the multipotent gastric stem cell and its committed daughters and subsequent development of gastric neoplasia. Parietal cell loss in inha(m1/m1) mice is not associated with this proliferative response. These different responses to parietal cell loss suggest that stimulation of ActRII-dependent signaling pathways in inha(m1/m1) animals affects the proliferative activity of the stem cell and its immediate descendents. This finding may have therapeutic significance.

Identification of an inhibin receptor in gonadal tumors from inhibin alpha-subunit knockout mice

Inhibins and activins are dimeric proteins that are functional antagonists and are structurally related to the transforming growth factor-beta (TGFbeta) family of growth and differentiation factors. Receptors for activin and TGFbeta have been identified as dimers of serine-threonine kinase subunits that regulate cytoplasmic proteins known as Smads. Despite major advances in our understanding of activin and TGFbeta receptors and signaling pathways, little is known about inhibin receptors or the mechanism by which this molecule provides a functionally antagonistic signal to activin. Studies described in this paper indicate that an independent inhibin receptor exists. Numerous tissues were examined for inhibin-specific binding sites, including the developing embryo, in which the spinal ganglion and trigeminal ganglion-bound iodinated inhibin A. Sex cord stromal tumors, derived from male and female inhibin alpha-subunit-deficient mice, were also identified as a source of inhibin receptor. Abundant inhibin and few activin binding sites were identified in tumor tissue sections by in situ ligand binding using iodinated recombinant human inhibin A and 125I-labeled recombinant human inhibin A. Tumor cell binding was specific for each ligand (competed by excess unlabeled homologous ligand and not competed by heterologous ligand). Based on these results and the relative abundance and homogeneity of tumor tissues versus the embryonic ganglion, tumor tissues were homogenized, membrane proteins were purified, and putative inhibin receptors were isolated using an inhibin affinity column. Four proteins were eluted from the column that bind iodinated inhibin but not iodinated activin. These data suggest that inhibin-specific membrane-associated proteins (receptors) exist.

Sclerosing stromal tumor of the ovary: a clinicopathologic, immunohistochemical, ultrastructural, and cytogenetic analysis with special reference to its vasculature

Sclerosing stromal tumor (SST) is a rare ovarian neoplasm occurring predominantly in young women and is histologically characterized by cellular heterogeneity, prominent vasculature, and a pseudolobular appearance composed of cellular and hypocellular areas. In the current study, three cases of SST were ultrastructurally examined and the tumors were found to be composed of several kinds of cells, i.e., luteinized thecalike cells, spindle-shaped fibroblastic cells, and primitive mesenchymal cells. These findings thus supported the ovarian stromal origin of SST. Twelve cases of SST also were analyzed immunohistochemically and demonstrated an expression of vascular permeability factor/vascular endothelial growth factor (VPF/VEGF) in the luteinized thecalike cells and its receptor, fms-like tyrosine kinase 1 (flt-1), in capillary to medium-sized blood vessels. Reverse transcription-polymerase chain reaction (RT-PCR) also showed an expression of VPF/VEGF messenger RNA in SSTs. Accordingly, the characteristic vasculature and edema of SSTs were considered to be associated with the expression of VPF/VEGF. In addition, a fluorescence in situ hybridization (FISH) analysis also showed cells with three copy number of chromosome 12 in 13-21% of all examined SST cells, which suggested the presence of chromosome 12 trisomy in SSTs as well as in other ovarian stromal tumors.

Inhibin and epithelial membrane antigen immunohistochemistry assist in the diagnosis of sex cord-stromal tumors and provide clues to the histogenesis of hypercalcemic small cell carcinomas

Ovarian sex cord-stromal tumors are a morphologically diverse group of neoplasms that can mimic the appearance of other ovarian tumors. Because the treatment and prognosis of sex cord-stromal tumors differs substantially from those of other ovarian neoplasms, the development of an immunohistochemical panel to support the diagnosis of the former group of tumors would be useful. In this report, the utility of immunostaining for inhibin alpha, epithelial membrane antigen, MIC2 gene protein product, and keratin in the differential diagnosis of sex cord-stromal tumors was assessed in formalin-fixed, paraffin-embedded sections. In addition, the immunohistochemical staining pattern of ovarian small cell carcinomas (SCCs), hypercalcemic type, was analyzed in an attempt to clarify the histogenesis of these tumors. Thirty-two (97%) of 33 granulosa cell tumors (GCTs), 10 (91%) of 11 Sertoli-Leydig cell tumors (SLCTs), and 4 (8%) of 51 carcinomas showed inhibin alpha immunopositivity. None of the 3 lymphomas, 5 carcinoids, 6 dysgerminomas, or 12 SCCs showed inhibin alpha positivity. Eighteen (55%) GCTs, 6 (55%) SLCTs, 6 (12%) carcinomas, and 7 (58%) SCCs showed MIC2 gene expression. None of the GCTs and only one SLCT showed epithelial membrane antigen (EMA) positivity, although 92% of surface epithelial carcinomas and 75% of SCCs were immunoreactive. These data suggest that detection of inhibin immunoreactivity in an ovarian tumor that is EMA-negative provides both sensitive and specific support for the diagnosis of a sex cord-stromal tumor. Because SCCs generally stain for EMA but not for inhibin, it appears that SCCs probably represent a variant of surface epithelial tumor rather than a type of sex cord-stromal tumor.

Estrogen secretion from a malignant sex cord stromal tumor in a patient with complete androgen insensitivity

We report on a 68-year-old patient with complete androgen insensitivity syndrome (testicular feminization syndrome) in whom an estrogen-secreting malignant sex cord stromal tumor developed in an intraabdominal testis. We believe this to be the first such case to document estrogen secretion by the tumor.

Inhibin immunohistochemistry applied to ovarian neoplasms: a novel, effective, diagnostic tool

Immunohistochemistry using monoclonal antibodies against human inhibin, a peptide hormone produced by ovarian granulosa cells to inhibit follicle-stimulating hormone (FSH), has been recently applied to diagnostic anatomic pathology. This investigation hypothesizes that inhibin immunohistochemistry will aid in the crucial clinical distinction between sex cord-stromal and other primary ovarian neoplasms. Available H&E slides and clinical information from a retrospective surgical series of 186 primary ovarian tumors were reviewed to verify diagnoses, and representative paraffin sections were immunostained with anti-inhibin (R1 monoclonal, Serotec, Kidlington, Oxford, UK). Immunoreactivity was graded as weak/strong (W/S), and the proportion of strong staining cells was coded as follows: S1 = <10%, S2 = 10%-50%, S3 = >50%, respectively. Inhibin immunoreactivity for 137 sex cord-stromal lesions was as follows: 100% of 66 granulosa cell tumors: 80% S3, 20% S2; 100% of 17 Sertoli-stromal tumors: 90% S3, 10% S2; 100% of 13 hyperplastic follicular/stromal lesions: 90% S3, 10% S2; 100% of six steroid cell tumors: 100% S3; 90% of 18 thecomas: 40% S3, 10% S2, 10% S1, 30% W; 0% of 12 fibromas, three myxomas, and two sclerosing stromal tumors. None (0 of 49) of the other ovarian neoplasms exhibited inhibin: 22 carcinomas, 12 carcinosarcomas, seven small cell carcinomas, six germ cell tumors, and two lymphomas. In the typical case, the distinction between sex cord-stromal and other ovarian neoplasms requires nothing more than routine pathological examination. In diagnostically challenging cases, our data indicate that inhibin immunohistochemistry is a very useful adjunct because granulosa and sertoli-stromal tumors are positive whereas other potential mimickers have been negative thus far.

Immunohistochemistry of unclassified sex cord-stromal tumors of the testis with a predominance of spindle cells

Unclassified sex cord-stromal tumors (SCSTs) of the testis comprised predominantly of spindle cells can be difficult to classify. To achieve better definition of these tumors, we examined the histologic, histochemical, and ultrastructural features of four unclassified SCSTs with spindle-cell features, and compared their immunohistochemical features with those of 24 other SCSTs of the testis and ovary. Three of the spindle-cell tumors were composed of relatively short spindled cells with prominent nuclear grooves and intermixed epithelioid cells. All of the three were located adjacent to the rete testis. The fourth case consisted of elongate spindle cells that were reminiscent of smooth muscle. In all of the four cases, reticulin enveloped aggregates of cells of various sizes but not individual cells. Ultrastructural analysis of two of the spindle-cell tumors revealed desmosomes, numerous thin filaments, and focal dense-bodies. Immunohistochemically, all of the four tumors were reactive for S-100 protein and smooth muscle actin. Staining for S-100 protein and smooth muscle actin was also observed in three of six granulosa cell tumors and both juvenile granulosa cell tumors. Although variable staining for S-100 protein was found in 5 of the 12 other SCSTs (4 Leydig cell, 6 Sertoli-Leydig cell, and 2 unclassifiable ovarian SCSTs), reactivity for smooth muscle actin was present in only 1 Sertoli-Leydig cell tumor. In contrast, all of the four ovarian fibromas/thecomas were reactive for smooth muscle actin but failed to stain for S-100 protein. Taken together, the histologic, histochemical, immunohistochemical, and ultrastructural features of the spindle-cell tumors are similar to those of granulosa cell tumors. Reactivity for S-100 protein and smooth muscle actin is characteristic of these tumors. These tumors should be distinguished from other unclassified SCSTs.

Alpha and beta subunits of inhibin/activin as sex cord-stromal differentiation markers

Inhibins (alpha and beta heterodimers) and activins (beta homodimers) are related peptides with opposing biologic action on gonadotropin regulation. They serve as components of the pituitary-gonadal feedback system. Although sex-cord stromal tumors can usually be distinguished from ovarian epithelial tumors or their metastases by morphology or by using antibodies against intermediate filaments, the diagnosis remains difficult in rare situations in such cases as sarcomatoid granulosa-theca cell tumors, ovarian small cell carcinomas, or soft-tissue sarcomas. A total of 28 sex cord-stromal tumors of the ovary and 43 non-sex cord-stromal tumors were immunohistochemically evaluated for the presence of alpha and beta subunits of inhibin and activin. For comparison, 10 normal adult gonads including seven ovaries with hilar regions and three testes also were examined. Immunoreactivity for both alpha and beta subunits of inhibin/activin was identified in both non-neoplastic and neoplastic granulosa, Sertoli, Leydig, hilar and luteinized theca cells, with the strongest immunoreactivity in Leydig and hilar cells. One of three Sertoli-Leydig cell tumors that showed a sarcomatoid growth pattern and one sex-cord tumor with annular tubules also were immunoreactive for both subunits. For non-sex cord stromal-derived ovarian tumors, alpha subunit immunoreactivity was negative in all but two of five ovarian mucinous tumors. Weak immunoreactivity for beta subunit was found in most ovarian surface epithelial carcinomas, two of four colonic, and one of three pancreatic carcinomas. No immunostaining was found in nonspecialized gonadal stromal or interstitial cells, thecal cells, germ cells, ovarian small cell carcinomas, carcinoid tumors, dysgerminomas, or leiomyosarcomas. Immunostaining of alpha subunit (inhibin alpha), but not of beta subunit could serve as a sex cord-stromal differentiation marker because alpha subunit alone is largely confined to sex cord-stromal lesions with the exception of some ovarian mucinous tumors. Further studies are needed to define the usefulness of this sex cord-stromal differentiation marker in the practice of surgical pathology. Coexpression of alpha and beta subunits in sex cord-stromal elements suggests that dimeric inhibin is expressed in these cells.

Use of monoclonal antibody against human inhibin as a marker for sex cord-stromal tumors of the ovary

Inhibin is a glycoprotein hormone produced by normal ovarian granulosa cells and testicular sertoli cells. In the ovary, it inhibits the secretion of follicle-stimulating hormone. Patients with granulosa cell tumors (GCT) have elevated serum levels of inhibin and this finding has been used to detect recurrent tumor. This study attempts to determine whether inhibin antibody (IAB) can preferentially mark GCT and Sertoli-cell or Sertoli-Leydig cell tumors (SCT) in paraffin-embedded tissues and facilitate distinction of GCT from small cell carcinoma of hypercalcemic type (SCC), SCT from Sertoliform endometrioid carcinoma (SEC), and primitive gonadal-stromal tumors from a variety of poorly differentiated neoplasms. Applying microwave-enhanced immunohistochemistry, a total of 126 paraffin-embedded and microwave-enhanced archival ovarian tumors and tissues were studied by using monoclonal IAB. The tumors included 32 adult GCT, 7 juvenile GCT, 4 metastatic GCT, 8 SCT, 7 SCC, 6 primitive gonadal stromal tumors (PGST), 5 fibrothecomas, 6 lipid cell tumors (LCT), 5 extrauterine endometrial stromal sarcomas (ESS), 5 hemangiopericytomas (HPC), 1 metastatic malignant melanoma, 1 metastatic malignant lymphoma, and 27 epithelial tumors including 8 SEC, 5 mucinous tumors, and 4 Brenner tumors. Seven pregnancy luteomas (nodular theca lutein hyperplasia of pregnancy), 3 corpora lutea and 2 ovarian follicles were also studied. The intensity of immunostaining was scored from one to three and the percentage of the immunoreactive tumor cells was determined and expressed in 10% increments. Among 32 adult GCT, 31 (97%) tumors reacted positively with IAB. The percent of positive cells ranged from 30% to 100% (average 80%). Similarly, all four metastatic GCT, 7 juvenile GCT and 4 of 5 fibrothecomas were immunoreactive with monoclonal IAB. Seven of 8 (88%) SCT, 5 of 6 (83%) PGST, all 6 LCT, 7 pregnancy luteomas, 3 corpora lutea and the 2 ovarian follicles were also positive with IAB. The most intense positivity was observed in luteinized stromal cells regardless of tumor type. No immunoreactivity was observed in any of the 7 SCC, 5 ESS, 5 HPC, 1 metastatic malignant melanoma, 1 metastatic malignant lymphoma and the epithelial component of all 27 epithelial tumors including 8 SEC. Among the mucinous tumors of the ovary, however, 3 tumors with luteinized stromal cells showed immunoreactivity in these cells, but no positivity was seen in the mucinous epithelium. We conclude that IAB is an excellent marker for sex cord differentiation in ovarian tumors. It can be used effectively in the diagnosis of GCT and its distinction from epithelial neoplasms particularly SCC. The IAB may also be helpful in differentiating LCT from epithelial malignancies. However, it cannot be used to distinguish GCT from SCT.

The site of inhibin production in ovarian neoplasms

Inhibin, a physiological product of ovarian follicle cells, normally absent in serum of postmenopausal women, is elevated in adult granulosa cell tumours of the ovary. Recently, high serum levels of inhibin were reported in carcinomas and, surprisingly, also in Krukenberg tumours of the ovary. This study attempted to determine the site of inhibin production in primary (111 cases), metastatic (13) and secondary (10) ovarian tumours by using immunohistochemistry. Positive staining in tumour cells was encountered in all cases of sex-cord- stromal cell tumours, adult (13) and juvenile (3) granulosa cell tumours, thecofibromas (10), in a lipid cell tumour (1) and a Sertoli-Leydig cell tumour (1). Primary and secondary tumours not derived from sex-cord stroma revealed no positivity in tumour cells, but in theca-like cells in the surrounding non-neoplastic ovarian stroma. A positive reaction was not observed in non-tumour-bearing ovaries of a control group. The ovarian inhibin of postmenopausal women is derived from activated sex-cord stroma or sex-cord-stromal neoplasms. Therefore, elevated serum inhibin concentrations in women with primary or secondary ovarian neoplasms with other histogenesis seem to be due to an activation of the non-neoplastic ovarian stroma. Inhibin will fail to be a tumour marker in these cases. By contrast, it will be useful in proving sex-cord differentiation by immunohistochemistry and might be used in surveillance of malignant sex-cord derived neoplasms by serum assays.

Activin signaling through activin receptor type II causes the cachexia-like symptoms in inhibin-deficient mice

Activins and inhibins, members of the transforming growth factor-beta superfamily, are involved in diverse physiological and developmental processes. We have previously shown that mice deficient in alpha-inhibin develop gonadal sex cord-stromal tumors at an early age. The tumor development is rapidly followed by a wasting syndrome that includes severe weight loss, hepatocellular necrosis around the central vein, and depletion of the parietal cells in the glandular stomach. The liver histology in inhibin-deficient mice is similar to the pathological effects of short-term treatment of rats and mice with recombinant activin A. Consistent with these findings, we have shown that the gonadal tumors in the inhibin-deficient mice secrete high levels of activins. In addition, Northern blot analysis has localized activin receptor type II (ActRII) to the liver. Based on these studies, we postulated that tumor-produced activins act through ActRII to cause the wasting syndrome in inhibin-deficient mice. To test this hypothesis and determine the significance of elevated levels of activin signaling through ActRII in vivo, we generated compound homozygous mutant mice deficient in both alpha-inhibin and ActRII. Despite the continued development of gonadal sex cord-stromal tumors and elevated serum levels of activin A and B, the compound homozygous mutant mice suffered no unusual weight loss, and the stomachs and livers of the majority of the mice were histologically normal. These results demonstrate that increased levels of activin signaling through ActRII in hepatocytes and the glandular stomach causes the hepatocellular necrosis and depletion of parietal cells in the glandular stomach as well as the severe weight loss in vivo.

Immunohistochemical localization of Ad4-binding protein with correlation to steroidogenic enzyme expression in cycling human ovaries and sex cord stromal tumors

Ad4-binding protein (Ad4BP) has been demonstrated recently as a transcription factor that serves as a general regulator of all steroidogenic P450 genes. We examined the expression of Ad4BP in 32 normal cycling human ovaries and 22 human ovarian sex cord stromal tumors by immunoblotting and immunohistochemistry. Immunoblotting of normal cycling human ovaries revealed a single band of 53 kilodaltons, corresponding to the mol wt of Ad4BP. We also correlated Ad4BP expression with the immunolocalization of the steroidogenic enzymes (side-chain cleavage cytochrome P450, cytochrome P450 17 alpha-hydroxylase, and cytochrome P450 aromatase). Ad4BP immunoreactivity, which was present only in the nuclei, was observed sporadically in the granulosa cells and adjacent stromal cells in the preantral follicles. In the dominant antral follicles, Ad4BP was detected in both granulosa and theca interna cells. However, in the nondominant antral follicles, Ad4BP was observed only in theca interna cells. In the corpus luteum, Ad4BP was present in both luteinized granulosa and thecal cells. Ad4BP was also expressed in some atretic follicles and degenerating corpora lutea. The spatial and temporal localization of Ad4BP in the normal cycling human ovary generally correlated well with that of steroidogenic enzymes. However, expression of the steroidogenic enzymes followed that of Ad4BP during the developing stages of the preantral follicle and vice versa during the process of follicular atresia. In ovarian sex cord stromal tumors, Ad4BP expression was observed in tumor cells that were positive for steroidogenic enzymes, but not in nonsteroidogenic tumor cells. These results, especially the in situ colocalization of Ad4BP and the steroidogenic enzymes, suggest that Ad4BP has the potential to control steroidogenic P450 expression in both normal and pathological human ovaries.

[An ovarian sex cord tumor with annular tubules secreting prolactin. Reality or fortunate coincidence?]

In a 13-year old girl, an ovarian tumor was suspected of being responsible for causing amenorrhea-galatorrhea. In the absence of any abnormality of the medial umbilical folds, hormonal assessment indicated a high level of prolactin, which was restored to normal after exeresis of the mass. This was an ovarian tumor of the sexual cords with annelated tubules (SCTAT de Scully).