Sertoliform Endometrioid Carcinoma Research Articles

Intraoperative frozen section evaluation of ovarian sex cord-stromal tumours and their mimics: a study of 121 cases with emphasis on potential diagnostic pitfalls

Ovarian sex cord-stromal tumours (SCSTs) present diagnostic difficulties during frozen section (FS) consultations due to their diverse morphology. This study aimed to evaluate the accuracy of FS evaluation of SCSTs in our institution, as well as to examine the reasons leading to incorrect FS diagnosis. Cases mimicking SCSTs and diagnosed as such during FS were also highlighted. We analysed 121 ovarian SCST cases and their mimics which underwent FS consultations over a 10-year period, to evaluate FS accuracy, reasons for deferrals and discrepancies. FS diagnoses were concordant, deferred and discrepant compared to the final diagnosis in 50 (41.3%), 39 (32.2%) and 32 (26.5%) cases, respectively. Major discrepancies (9/121, 7.4%) were mostly related to the diagnosis of adult granulosa cell tumour (AGCT). A fibromatous AGCT was misinterpreted as fibroma on FS, while a cystic AGCT was called a benign cyst. Conversely, a mesonephric-like adenocarcinoma, a sertoliform endometrioid carcinoma and a thecoma were misinterpreted as AGCT on FS. Another discrepant case was a Krukenberg tumour with prominent fibromatous stroma in which malignant signet ring cells were overlooked and misinterpreted as fibroma. Minor discrepancies were primarily associated with fibroma (21/23, 91.3%), wherein minor but potentially impactful details such as cellular fibroma and mitotically active cellular fibroma were missed due to sampling issues and misinterpretation as leiomyoma. FS evaluation for ovarian SCSTs demonstrated an overall accuracy of 78.5%, 81.0% and 81.8% for benign, uncertain/low malignant potential and malignant categories, respectively. There was no FS-related adverse clinical impact in all cases with available follow-up information (120/121 cases). Intraoperative FS evaluation of ovarian SCSTs is challenging. A small number of cases were misinterpreted, with AGCTs being the primary group where errors occur. Awareness of common diagnostic pitfalls and difficulties, alongside application of a stepwise approach, including (1) obtaining comprehensive clinical information, (2) thorough macroscopic examination and directed sampling, (3) meticulous microscopic examination with consideration of pitfalls and mimics, (4) effective communication with surgeons in difficult cases, and (5) consultation of subspecialty colleagues in challenging cases, will enhance pathologists' reporting accuracy and management of such cases in the future.

Sertoliform endometrioid carcinoma of the right ovary.

Endometrioid carcinomas of the ovary are a subtype of epithelial ovarian tumors, with sertoliform endometrioid carcinomas being a rare variant. We report a case of a previously healthy premenopausal woman presenting with androgenic symptoms in the form of hirsutism and male pattern alopecia. On further testing, she was found to have high levels of luteinizing hormone and total testosterone levels, and imaging revealed a large pelvic abdominal mass in the right ovary. She underwent total hysterectomy with bilateral salpingo-oophorectomy. Microscopy and histopathology confirmed the diagnosis of sertoliform endometrioid carcinoma. Her symptoms improved significantly on follow-up. Androgenic tumors might not be common in premenopausal women; however, it is important to maintain a high level of suspicion in patients presenting with virilizing symptoms especially of rapid progression. Our 47-year-old patient presented with virilizing symptoms that were rapidly progressing, which raises the suspicion of an underlying androgen secreting neoplasm. Sertoliform endometrioid carcinoma (SEC) is an extremely rare variant of endometrioid carcinomas and tend to present at an earlier stage as compared to most endometrioid carcinomas of the ovary. Recognition of SEC in virilizing patients is important as it is a well-differentiated, low-grade malignancy with a good prognosis when confined to the ovary.

Sertoliform Endometrioid Carcinomas of the Right Ovary

Abstract Background: Endometrioid carcinomas of the ovary are a sub-type of epithelial ovarian tumors. The vast majority are malignant and invasive. On imaging, they are usually characterized as complex nonspecific solid-cystic masses and found associated with endometriosis. However, endometrioid carcinoma of ovary resembling sex cord-stromal tumor is a rare variant of endometrioid adenocarcinoma that focally looks like a sex cord-stromal tumor with sertoli, leydig, or granulosa cells. Sertoliform endometrioid carcinoma of the ovary (SEC) is one variant that bears histologic similarity to Sertoli and Sertoli-Leydig cell tumors (SLTs). Clinical Case: A 47 year old, premenopausal female, presented with rapid growing hirsutism, frontal hair loss, abdominal distension and constipation for less than one year. On clinical examination modified Ferriman-Gallwey (mFG) score was 17/36. Abdominal examination showed a palpable mass in lower abdomen, 25cm in size, rounded, and hard in nature. CT abdomen and pelvis revealed large pelvic abdominal mass (21x20.5x17 cm) with cystic and basal soft tissue components related to right ovary. Preoperatively laboratory investigations showed FSH 9.96 mIU/mL, LH 15.4, Estradiol (E2) 94.7 pg/ml, raised total testosterone 4.38 nmol/l, normal SHBG 34 nmol/l and normal DHEA-S 161 microg/dl. Total abdominal hysterectomy and bilateral salpingo-oophorectomy was done, in which the right ovary was seen to be replaced by a solid cystic tumor with ruptured capsule. Grossly, the right ovary was enlarged measuring 9.5 cm × 8 cm × 4.8 cm. Microscopy showed round to solid tubules lined by pseudostratified columnar epithelium with elongated nuclei resembling sertoli tumor-like pattern along with conventional endometrioid tumor. A histopathological diagnosis of SEC of right ovary was made. Immunohistochemistry showed tumor cells strongly immunoreactive for epithelial membrane antigen (EMA), cytokeratin (CK) but negative for inhibin, thus confirming the diagnosis of SEC of right ovary. Conclusion: SEC is extremely rare variant of endometrioid carcinomas and tend to present at an earlier stage as compared with most endometrioid carcinomas of the ovary. Recognition of SEC in virilizing patients is important as it is a well-differentiated, low-grade malignancy that displays a good prognosis when confined to the ovary.

Sertoliform Endometrioid Carcinoma of the Ovary in a Young Woman: Diagnostic Challenges for the Pathologist

Sertoliform endometrioid carcinoma (SEC) is a rare variant of ovarian endometrioid carcinoma commonly affecting older women. The morphology of this tumour closely resembles that of Sertoli and Sertoli–Leydig cell tumours. Microscopically, the tumour is composed of anastomosing cords, nests, trabeculae and tubules lined by pseudostratified columnar epithelium with elongated nuclei. We present a case of Sertoliform endometrioid carcinoma in a 24-year-old woman. A 24-year-old woman presented with lower abdominal pain and bleeding per vagina for the past 6 months associated with loss of weight and appetite. Ultrasound abdomen showed a complex pelvic mass. Positron emission tomography–computed tomography scan showed complex abdominopelvic mass with metastatic peritoneal and omental nodules, moderate ascites and right pleural thickening. Complete cytoreduction was performed. On microscopy, both ovaries showed infiltration by a malignant neoplasm composed of cells arranged as sheets, trabeculae, nests and focal tubules lined by moderately pleomorphic cells with elongated ovoid hyperchromatic nuclei, inconspicuous nucleoli and scant cytoplasm. Focally, cribriform pattern was noted with tall columnar lining epithelium showing nuclear stratification. The tumour cells were positive for cytokeratin, epithelial membrane antigen, oestrogen receptor and progesterone receptor and negative for p53, synaptophysin, chromogranin, CD99, inhibin and calretinin. A diagnosis of Sertoliform endometrioid carcinoma of the ovaries was rendered. To our knowledge, only a single case report has been published so far where SEC presented in a woman in her twenties. We would like to emphasise with this case the need to include SEC as a differential diagnosis for tumours with sex cord stromal components seen in younger women and to reiterate the importance of adequate and thorough sampling of the tumour to look for conventional endometrioid carcinoma areas.

A novel clinicopathological analysis of early stage ovarian Sertoli-Leydig cell tumors at a single institution.

ObjectiveTo evaluate the clinical and pathologic characteristics of patients who were diagnosed with ovarian Sertoli-Leydig cell tumors (SLCTs) in a single institution.MethodsThe medical records of 11 patients who were pathologically diagnosed with SLCTs beginning in 1995 in a single institute was reviewed.ResultsThe median patient age was 31 years (range, 16 to 70 years). Patient International Federation of Gynecology and Obstetrics stages were IA, IC, and IIB in 3 (27.3%), 6 (54.5%), and 2 (18.2%) patients, respectively. Six patients (54.5%) had grade 3 tumors, 3 patients (27.3%) had grade 2 tumors, and 1 patient (9.1%) had a grade 1 tumor. Four patients without children underwent fertility-sparing surgery, and 7 patients had full staging surgery, including a hysterectomy and bilateral salpingo-oophorectomy, with a laparoscopic approach used in 3. Eight patients underwent pelvic lymph node dissection, and 8 patients were administered adjuvant chemotherapy consisting of bleomycin, etoposide, and cisplatin in 6 cases, a modified bleomycin, etoposide, and cisplatin regimen in 1 case, and a combined paclitaxel and cisplatin regimen in 1 case. Two patients died of disease and were re-diagnosed with Sertoli form endometrioid carcinoma. The other patients remain alive without recurrence at the time of reporting.ConclusionOur findings suggest that regardless of tumor stage or grade, ovarian SLCT patients have a good prognosis. Close observation and unilateral salpingo-oophorectomy would be beneficial for women who still wish to have children, while hysterectomy and bilateral salpingo-oophorectomy with adjuvant chemotherapy would be the optimal treatment in other cases. Furthermore, meticulous pathologic diagnosis is needed to develop a precise treatment strategy.

Stage I ovarian cancer cases during early, mid and late pregnancy periods: Three case reports and review of the literature

Since ovarian cancer during pregnancy is rare, the decisions regarding pregnancy discontinuation or fertility preservation are often difficult. We report three ovarian cancer cases detected at early, mid and late pregnancy periods in which both babies and mothers were saved. In particular, case 2 is the first reported instance of a sertoliform endometrioid carcinoma of the ovary during pregnancy. In addition, we review the clinical characteristics of previously reported patients with stage I ovarian cancer diagnosed during pregnancy. Even with stage Ia ovarian cancer, restaging laparotomy at cesarean section or post-delivery may be important to determine the treatment plan because staging during pregnancy is rarely complete.

Diagnostic Utility of WT1 Immunostaining in Ovarian Sertoli Cell Tumor

WT1, the Wilms tumor gene product, can be expressed in various tumors from different anatomic sites, including some types of ovarian tumors. Regarding the latter, most studies have focused on surface epithelial-stromal tumors in which serous carcinomas are usually positive and endometrioid carcinomas are negative. Very few studies have specifically investigated this marker in ovarian sex cord-stromal tumors; however, limited data in the literature suggest that WT1 may be frequently expressed in sex cord-stromal tumors. As pure Sertoli cell tumor can be in the histologic differential diagnosis of endometrioid tumors (particularly borderline tumor and carcinoma) and carcinoid, immunostaining for WT1 might be of diagnostic value. Immunohistochemical staining for WT1 was performed in 108 ovarian tumors: pure Sertoli cell tumor (n=26), endometrioid borderline tumor (n=25), classic well-differentiated endometrioid carcinoma (n=23), sertoliform endometrioid carcinoma (n=12), and carcinoid (n=22). Additionally, inhibin and calretinin immunostaining were performed in all cases of Sertoli cell tumor for purposes of comparing expression with WT1. Extent of immunostaining was scored on a 0 to 4+ semiquantitative scale, and immunohistochemical composite scores based on a combination of extent and intensity of immunostaining were calculated in positive cases (possible range, 1 to 12). Nuclear expression of WT1 was present in 96% of Sertoli cell tumors, 16% of endometrioid borderline tumors, 13% of classic well-differentiated endometrioid carcinomas, 25% of sertoliform endometrioid carcinomas, and 0% of carcinoids. In Sertoli cell tumors, expression was diffuse (>50% of positive cells) in all positive cases. When positive in the non-Sertoli cell tumors, the extent of expression tended to be focal to patchy (50% or less positive cells). In Sertoli cell tumors, inhibin and calretinin were expressed in 96% and 54% of cases, respectively. The extent of expression of inhibin tended to be diffuse, similar to WT1; however, the extent of immunostaining for calretinin tended to be focal to patchy. The immunohistochemical composite scores for WT1, inhibin, and calretinin were 11.2, 7.6, and 4.8, respectively. Coordinate patterns for the extent of expression of WT1, inhibin, and calretinin in pure Sertoli cell tumor showed that all 3 markers were positive in 54% of cases; however, 42% were positive for WT1 and inhibin but negative for calretinin. In cases positive for both WT1 and inhibin, expression of both markers was diffuse in 84% of cases, but WT1 was diffuse while inhibin was focal to patchy in 16% of cases. We conclude that ovarian Sertoli cell tumor should be added to the growing list of WT1-positive tumors. This marker is useful for the distinction of Sertoli cell tumor from endometrioid tumors and carcinoid. The diagnostic utility of WT1 in Sertoli cell tumor is similar to inhibin but better than that of calretinin.

Sertoliform Endometrioid Carcinoma of the Endometrium With Dual Immunophenotypes for Epithelial Membrane Antigen and Inhibin ??

We report a rare case of sertoliform endometrioid carcinoma of the endometrium in a 71-year-old African American woman who presented with postmenopausal bleeding. Her medical condition was remarkable for hypertension, diabetes, and obesity. She underwent total hysterectomy, right salpingo-oophorectomy and lymph node sampling. The endometrium was occupied by a 4.5-cm solid polypoid tumor, which grossly invaded into the myometrium. Microscopically, the tumor consisted of small hollow tubules, anastomosing cords and trabeculae, and tightly packed nests. Microglandular areas mimicking adult granulosa cell tumors were also present. But true Call-Exner bodies were absent. Component of typical endometrioid carcinoma was noted only focally. The uninvolved endometrium demonstrated atypical complex hyperplasia. The tumor cells were diffusely immunoreactive for epithelial membrane antigen, estrogen receptor, and progesterone receptor (PR), and focally for vimentin. The tumor cells were also diffusely positive for inhibin alpha and CD99. Immunostains for other sex cord markers (calretinin, WT-1, and Melan-A) were also positive in approximately 30% to 40% of the tumor cells. Immunostains for CD10, smooth muscle actin, desmin, or HHF35 were negative. Two ovarian sertoliform endometrioid carcinomas from our archived tissue were, however, immunoreactive for epithelial membrane antigen but negative for inhibin alpha. Despite the prominent sertoliform features, both histologically and immunohistochemically, the tumor was of a high-grade endometrial carcinoma and will likely behave as such. As of today, dual differentiation of epithelium and sex cord by immunohistochemical staining has not been demonstrated in sertoliform endometrioid carcinomas of either endometrial or ovarian origin. Our case is the first documentation of such example and suggests that endometrial carcinoma can undergo true sex cord differentiation.

Sertoliform endometrioid carcinoma of the ovary: a potential diagnostic pitfall.

Sertoliform endometrioid carcinoma of the ovary (SEC) is an uncommon variant that bears histologic similarity to Sertoli and Sertoli-Leydig cell tumors (SLTs). Clinically, SEC affects an older population (60-70 years), while patients with SLT have an average age of 25 years and may exhibit endocrine manifestations. A number of histologic features can be used to distinguish the 2 entities, the most important ones being (1) the presence of areas with the usual pattern of endometrioid carcinoma, and (2) the presence of mucin at the apical borders of the tumor cells. Cytokeratin stains positively, while inhibin and calretinin stain negatively in SEC; the converse is true for SLTs. Based on the clinicopathologic behavior of this entity, SEC should be considered a well-differentiated carcinoma with relatively good prognosis if limited to the ovary.

Comparative Analysis of Alternative and Traditional Immunohistochemical Markers for the Distinction of Ovarian Sertoli Cell Tumor From Endometrioid Tumors and Carcinoid Tumor

The main neoplasms in the differential diagnosis for primary ovarian tumors with a tubule-rich pattern are pure Sertoli cell tumor, endometrioid tumors (including borderline tumor, well-differentiated carcinoma, and the sertoliform variant of endometrioid carcinoma), and carcinoid tumor. Because traditional immunohistochemical markers [pan-cytokeratin (pan-CK), low molecular weight cytokeratin (CK8/18), epithelial membrane antigen (EMA), inhibin, calretinin, CD99, chromogranin, and synaptophysin] can occasionally have diagnostic limitations, the goal of this study was to determine whether or not any alternative markers [cytokeratin 7 (CK7), estrogen receptor (ER), progesterone receptor (PR), CD10, and CD56] have better diagnostic utility when compared with traditional markers for this differential diagnosis. Immunohistochemical stains for alternative, as well as traditional, markers were performed on the following primary ovarian tumors: pure Sertoli cell tumor (n = 40), endometrioid borderline tumor (n = 38), sertoliform endometrioid carcinoma (n = 13), well-differentiated endometrioid carcinoma (n = 27), and carcinoid tumor (n = 42). Extent and intensity of immunostaining were semiquantitatively scored. In addition, immunohistochemical composite scores (ICSs) in positive cases were calculated on the basis of the combination of extent and intensity scores. Cytokeratin 7 (CK7) was positive in 97% of endometrioid tumors, 13% of Sertoli cell tumors, and 24% of carcinoid tumors. The differences in the mean ICSs for endometrioid tumors versus Sertoli cell tumor or carcinoid tumor were statistically significant (P values ranging from <0.001 to 0.018). ER and PR were positive in 87% and 86% of endometrioid tumors, 8% and 13% of Sertoli cell tumors, and 2% each of carcinoid tumors, respectively. The differences in the mean ICSs for endometrioid tumors versus Sertoli cell tumor were statistically significant (P values ranging from <0.001 to 0.012). Among the epithelial markers, EMA seemed to be the most discriminatory but only slightly better than CK7, ER, or PR. Pan-CK and CK8/18 were not helpful. CD10 showed overlapping patterns of expression in all categories of tumors. Among the sex cord markers, CD10 was markedly less useful than inhibin or calretinin; CD99 was not discriminatory. CD56 showed overlapping patterns of expression in all categories of tumors. Among the neuroendocrine markers, CD56 was less useful than chromogranin or synaptophysin. When traditional immunohistochemical markers are problematic for the differential diagnosis of ovarian Sertoli cell tumor versus endometrioid tumors versus carcinoid tumor, adding CK7, ER, and/or PR to a panel of markers can be helpful. Endometrioid tumors more frequently express CK7, ER, and PR and show a greater extent of immunostaining in contrast to Sertoli cell tumor and carcinoid tumor. Compared with traditional epithelial markers, CK7, ER, and PR are nearly as advantageous as EMA. Inhibin is the most discriminatory sex cord marker, and CD10 is not helpful in the differential diagnosis. Chromogranin and synaptophysin are excellent discriminatory markers for carcinoid tumor, and CD56 is neither sufficiently sensitive nor specific enough for this differential diagnosis to warrant its use in routine practice.

Immunohistochemical Analysis of Sox9 in Ovarian Sertoli Cell Tumors and Other Tumors in the Differential Diagnosis

The distinction of ovarian Sertoli cell tumor from other tumors in the histological differential diagnosis, particularly endometrioid carcinoma and carcinoid tumor, may be difficult. Many immunohistochemical markers have been studied for this differential diagnosis, but currently available markers are neither 100% sensitive nor specific. Sox9 is a transcription factor involved in Sertoli cell differentiation in the testis. The role that this molecule plays in the pathogenesis of ovarian Sertoli cell tumors and the potential use as an immunohistochemical marker for differential diagnosis have not been investigated. Immunohistochemical staining for Sox9 was performed in 152 ovarian tumors: pure Sertoli cell tumor (n = 36), endometrioid borderline tumor (n = 38), well-differentiated endometrioid carcinoma (n = 26), sertoliform endometrioid carcinoma (n = 13), and carcinoid tumor (n = 39). Nuclear expression was considered positive. Extent and intensity of staining were semiquantitatively scored. In addition, immunohistochemical composite scores in positive cases (ranging from 1 to 12) were calculated based on the extent score multiplied by the intensity score. Sox9 was expressed in 44% of Sertoli cell tumors, 55% of endometrioid borderline tumors, 65% of well-differentiated endometrioid carcinomas, 39% of sertoliform endometrioid carcinomas, and 10% of carcinoid tumors. The mean Sox9 immunohistochemical composite scores in positive cases were 6.3 for Sertoli cell tumor, 5.3 for endometrioid borderline tumor, 8.0 for well-differentiated endometrioid carcinoma, 2.8 for sertoliform endometrioid carcinoma, and 6.8 for carcinoid tumor. The differences in the mean Sox9 composite scores between Sertoli cell tumor and the other tumor categories were not statistically significant (p values ranged from 0.092 to 0.523). We conclude that Sox9 is variably expressed in ovarian Sertoli cell tumor and other tumors that are in the differential diagnosis and, thus, is not helpful for immunohistochemical distinction. Understanding the role of Sox9 in the pathogenesis of ovarian Sertoli cell tumor requires further study.

Uterine Retiform Sertoli-Leydig Cell Tumor

We report a case of a retiform Sertoli-Leydig cell tumor of intermediate differentiation presenting as a uterine intracavity polypoid mass in a 63-year-old woman. In contrast to sertoliform endometrioid carcinoma and to hitherto reported uterine tumors resembling ovarian sex cord tumors (UTROSCTs), which are primarily characterized by tubular glands and solid tubules, this tumor, which most likely represents a UTROSCT, showed a large spectrum of histologic features typical of a genuine retiform Sertoli-Leydig cell tumor. The diagnosis was confirmed by a battery of immunohistochemical stains, which also served as a tool for differential diagnosis with other neoplasms. The tumor cells were positive for broad spectrum keratin (CK) CK18, vimentin, calretinin, and progesterone receptor. Only a few isolated cells stained for inhibin. The tumor cells were negative for CK7, CK5/6, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA), carbohydrate antigen 125 (CA125), thrombomodulin, 013 (CD99), melan A, alpha-fetoprotein (AFP), placental alkaline phosphatase (PLAP), alpha-1-antitrypsin, estrogen receptor, S100, neurone specific enolase (NSE), chromogranin, synaptophysin, desmin, caldesmon, and CD10. Divergent differentiation of uterine cells seems to be the most likely pathogenetic mechanism. To the best of our knowledge, no UTROSCT showing such a variety of histologic features indicative of a true sex cord tumor has been reported before.

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.