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Signet Ring Stromal Tumor of the Ovary Occurring in Conjunction with Brenner Tumor
Gynecologic Oncology 77, 323–326 (2000) doi:10.1006/gyno.2000.5763, available online at http://www.idealibrary.com on
CASE REPORT Signet Ring Stromal Tumor of the Ovary Occurring in Conjunction with Brenner Tumor 1 Alan W. Cashell, M.D.,* ,2 W. Gray Jerome, Ph.D.,† and Ernest Flores, M.D.* *Davis Memorial Hospital, Elkins, West Virginia 26241; and †Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157 Received October 11, 1999
Objective. A case is presented of a single ovarian mass that had elements of both signet ring stromal tumor of the ovary and Brenner tumor. Methods. The histologic features and the results of histocytochemical, immunohistochemical, and electron microscopic studies are presented. Results. The signet ring component of the mass demonstrated features consistent with the few other cases previously reported. A positive immunohistochemical stain for the peptide hormone inhibin provides additional evidence for an ovarian stromal origin for this tumor. Conclusion. The tumor produced no hormonally related symptoms and has shown no evidence of recurrence. Signet ring stromal tumor of the ovary is an uncommon benign tumor that may be confused with metastatic signet ring carcinoma. The significance of the signet ring cells is not certain. Their association with Brenner tumor has not been previously described. © 2000 Academic Press
Key Words: ovary; tumor; stromal; signet ring; Brenner tumor.
INTRODUCTION In 1976, Ramzy reported a previously undescribed primary ovarian neoplasm [1]. The tumor cells were highly vacuolated, resulting in what he perceived as a “signet-ring” appearance, similar to that commonly associated with Kru¨kenberg tumors. Histochemical and electron microscopic studies suggested a derivation from ovarian stromal cells. Four cases have since been described by Dickersin et al. [2] and one by Suarez et al. [3]. These tumors are benign and, from the established literature, appear to be quite rare. We report a signet ring stromal tumor of the ovary in association with an otherwise typical Brenner tumor. This neoplastic combination has not been previously reported. We 1
This work received financial support from Davis Memorial Hospital, Elkins, West Virginia. 2 To whom correspondence should be addressed. Fax: (304) 637-3527. E-mail: [email protected].
present histochemical, immunohistochemical, and ultrastructural studies of the signet ring elements, including an immunoperoxidase stain for the peptide hormone, inhibin. CASE REPORT A 52-year-old woman being seen for a routine yearly examination complained of unexplainable weight loss. Her past history was remarkable for a gunshot wound to the head in her teenage years. The physical examination revealed a cachectic appearance and long-standing neurologic and musculoskeletal deficits secondary to her previous injury. A pelvic examination revealed a left-sided adnexal mass. There was no pain or distention of the abdomen. A pelvic ultrasound and CT scan were performed, confirming a 7-cm left-sided mass suspicious for cancer. There was no clinical evidence of abnormal hormonal effect. A CA-125 level was within normal limits. The patient subsequently underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy and recovered without incident. MATERIALS AND METHODS Hematoxylin and eosin, periodic acid–Schiff (PAS), reticulin, and mucicarmine stains were performed on the ovarian mass after paraffin embedding. The reticulin stain was done by the method of Gridley. An immunoperoxidase stain for inhibin A was done using an antibody from Serotec Ltd. A mixedweight cytokeratin stain was done using a mixture of BioGenex AE1 and AE3 in a 1:40 dilution. Immunoperoxidase stains for smooth muscle actin, carcinoembryonic antigen (CEA), desmin, epithelial membrane antigen (EMA), and vimentin were performed using antibodies from BioGenex. An S-100 stain was done using an antibody from Dako. The CAM 5.2 antibody was purchased from Becton–Dickinson. For electron microscopy, the tissue containing the region of interest was removed from paraffin wax by overnight immersion in xylene. The deparaffinized tissue was rehydrated by
323
0090-8258/00 $35.00 Copyright © 2000 by Academic Press All rights of reproduction in any form reserved.
324
CASHELL, JEROME, AND FLORES
sequential incubation with a series of fluids containing decreasing percentages of ethanol (100% ethanol, 90% ethanol in distilled water, 75% ethanol, etc.). The tissue was then incubated in phosphate buffer, osmicated in 1% osmium tetroxide in phosphate buffer, dehydrated in a graded series of ethanol (increasing ethanol percentage), and embedded in epoxy resin. Following embedding, thick sections (0.5 m) were cut and then stained with toluidine blue to confirm the presence of signet ring cells. Following thin sectioning (80 nm) the tissue was viewed by electron microscopy at 80 keV. The volume of vacuoles as a percentage of cellular volume was determined by standard point count stereology [4]. PATHOLOGY With the adnexa removed, the uterus weighed 59 g and was unremarkable with a weakly proliferative endometrium. The right ovary had a tan surface and measured 2.4 ⫻ 1.2 ⫻ 0.7 cm. It was microscopically unremarkable with no evidence of neoplasia. The left ovary also had a tan lobulated surface and measured 5.5 ⫻ 2.4 ⫻ 1.4 cm. A thin-walled fluid-filled epithelial cyst measuring 6 cm in diameter was attached. Sectioning the ovary revealed a hard well-defined nodule with a firm mottled yellow to tan cut surface within the ovary and measuring up to 2.5 cm in diameter. Histologic examination of this mass revealed a circumscribed but unencapsulated tumor surrounded by a rim of postmenopausal ovarian stroma of varying thickness. Within the tumor were multiple vaguely circumscribed irregularly shaped areas of vacuolated cells occupying 20% of the mass (Fig. 1). Most of these cells contained a cytoplasmic vacuole large enough to displace the nucleus, creating a signet ring appearance. The nuclei had a slightly irregular contour, an open chromatin pattern, and single small nucleoli. They varied only slightly in size. No mitotic figures were seen. The remainder of the tumor was composed of a fibrous stroma with embedded nests of a Brenner (transitional cell) tumor. The epithelial nests of the Brenner tumor had no consistent spatial relationship to the signet ring cells but sometimes appeared nearby (Fig. 2). Some of the epithelial nests showed glandular structures. The Brenner nests were diffusely positive using a PAS reaction and focally positive with a mucicarmine stain. The signet ring cells showed a negative reaction for both stains. A reticulin stain showed a delicate network of fibers investing the signet ring cells as well as the surrounding fibrous stromal cells (Fig. 3). An immunoperoxidase stain for inhibin showed positive areas of staining within the majority of signet ring cells and in approximately half of the remaining stromal cells. The signet ring cells and the tumor stromal cells showed a diffuse positive reaction with the vimentin and actin stains. The signet ring cells demonstrated a negative staining reaction with mixed-weight cytokeratin, CAM 5.2, EMA, CEA, desmin, and S-100. The signet ring cell reactions to immunoperoxidase staining are summarized in Table 1.
Electron microscopy revealed a loose arrangement of cells interspersed between areas of collagen. The cells showed no evidence of basement membrane formation and junctional specializations between cells were not observed. Most of the cells had at least one to several large, clear vacuoles (Fig. 4). In some cells they occupied as much as 70% of the cross-sectional area and stereologic volume measurement revealed that they averaged 48% of the cell volume. Cytoplasm surrounding the vacuoles was often thin except in areas around the nucleus. Many smaller vacuoles were also present, giving a foamy appearance peripheral to the large vacuole. The origin of the majority of the vacuoles was not specifically determined, but most were surrounded by a single membrane. A few were formed by swollen mitochondria probably representing degenerative change. Some reticulin fibers were seen surrounding the cells consistent with the positive cytochemical stain. A few clusters of fibrillary material seen within the cells suggested phagocytosis. The nuclei were euchromatic with very little heterochromatin. Most showed only indistinct nucleoli. Many nuclei were indented. The cytoplasm contained abundant free ribosomes and moderately abundant endoplasmic reticulum (Fig. 5). Some of the latter had enlarged luminal diameters. In contrast, there were only modest numbers of mitochondria and a mature Golgi apparatus was observed only infrequently. DISCUSSION The signet ring stromal tumor of the ovary described by Ramzy is important to recognize because of its possible confusion with a metastatic Kru¨kenberg tumor [1]. Both of these entities are composed of cells largely filled by vacuoles. The signet ring stromal tumor, however, lacks the mitotic activity, the pleomorphism, and the hyperchromatic nuclei of Kru¨kenberg tumors. The origin of the tumor reported in this case from the ovarian stroma is supported by the positive immunohistochemical reaction to an inhibin antibody. Inhibin is a peptide hormone produced by ovarian granulosa and luteinized cells that prevents the release of follicle-stimulating hormone from the pituitary gland [5]. It is composed of ␣ and  subunits linked by disulfide bonds [5]. Antibodies to the ␣ chain have been used with immunohistochemical techniques to assist in the identification of ovarian granulosa cell tumors and other sex cord stromal tumors [5, 6, 7]. The negative chemical reactions of the signet ring cells for PAS and mucicarmine and the negative immunohistochemical reactions to mixed-weight cytokeratin, CAM 5.2, and EMA are strong evidence against a metastatic origin. The negative S-100, CEA, and desmin stains and the positive vimentin stain are consistent with previously reported cases [2, 3]. The positive smooth muscle actin was unexpected. However, a focal positive reaction for this antibody within a few signet ring cells was reported by Dickersin et al. in one of their series of four cases [2]. The study of Costa et al. [5] provides additional
FIG. 2.
FIG. 1. H&E-stained section showing one of the irregularly contoured clusters of signet ring cells, ⫻400. H&E-stained section showing the relationship of an epithelial Brenner tumor nest to nearby signet ring cells, ⫻400. FIG. 3. Reticulin stain shows fibers surrounding individual signet ring cells, ⫻400.
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TABLE 1 Immunoperoxidase Stain Results for Signet Ring Cells Actin CAM 5.2 CEA Desmin EMA Inhibin Mixed-weight cytokeratin S-100 Vimetin
⫹ ⫺ ⫺ ⫺ ⫺ ⫹ ⫺ ⫺ ⫹
evidence that the positive smooth muscle actin stain complements the inhibin stain result in supporting the stromal origin of the signet ring cells in our case. In their study, a positive smooth muscle actin stain was seen in more than 90% of their series of 52 granulosa cell tumors [8]. The reticulin fiber investment of individual signet ring cells is also consistent with previously published cases [2, 3]. Ultrastructurally, our tumor shared the many free ribosomes and endoplasmic reticulum of Ramzy’s description [1]. However, many of the nuclei of our tumor were deeply indented in contrast to those previously described. It is not known whether the signet ring cells represent a true neoplasm or a reactive change. The four cases reported by Dickersin et al. had evidence of different origins including one with ultrastructural and immunohistochemical features of an epithelial tumor [2]. The irregular geographic distribution of signet ring cells within an otherwise typical Brenner tumor and their histochemical and immunohistochemical evidence of
FIG. 5. Transmission electron micrograph. This cell has multiple large vacuoles (V) in the cytoplasm. In addition, the lumens of much of the rough endoplasmic reticulum are swollen (arrowheads). ⫻12,150; bar ⫽ 0.5 m.
stromal origin suggest that this may be a reactive process. The tumor has shown no evidence of recurrence in the 2 years following excision. ACKNOWLEDGMENTS The authors thank Dr. Stamatakos and Dr. Tavassoli of the Armed Forces Institute of Pathology for reviewing the slides of this case. We also thank Dr. Jeffrey Stead and the histology staff of West Virginia University for performing the inhibin stain and Martha Ward of North Carolina Baptist Hospital for performing the CAM 5.2 stain. Marc Bleigh of Davis Memorial Hospital did the remaining stains.
REFERENCES
FIG. 4. Transmission electron micrograph. A signet ring cell has a very open nucleus with only minimal heterochromatin visible (arrowheads). Several very large vacuoles (V) and a number of smaller vacuoles are prominent in the cytoplasm. ⫻9800; bar ⫽ 1 m.
1. Ramzy I: Signet-ring stromal tumor of ovary. Cancer 38:166 –172, 1976 2. Dickersin GR, Young RH, Scully RE: Signet-ring stromal and related tumors of the ovary. Ultrastruct Pathol 19:401– 419, 1995 3. Suarez A, Palacios J, Burgos E, Gamallo C: Signet-ring stromal tumor of the ovary: A histochemical, immunohistochemical and ultrastructural study. Virchow’s Arch A Pathol Anat 422:333–336, 1993 4. Weibel ER: Stereological Methods. Vol. 1: Practical Methods for Biological Morphometry, San Diego, CA, Academic Press, 1979 5. Costa MJ, Ames PF, Walls J, Roth LM: Inhibin immunohistochemistry applied to ovarian neoplasms: A novel, effective, diagnostic tool. Hum Pathol 28:1247–1254, 1997 6. Zheng W, Sung CJ, Hanna I, DePetris G, Lambert-Messerlian G, Steinhoff M, Lauchlan SC: ␣ and  subunits of inhibin/activin as sex cord–stromal differentiation markers. Int J Gynecol Pathol 16:263–271, 1997 7. Flemming P, Wellmann A, Maschek H, Lang H, Georgii A: Monoclonal antibodies against inhibin represent key markers of adult granulosa cell tumors of the ovary even in their metastases. Am J Surg Pathol 19:927– 933, 1995 8. Costa MJ, DeRose PB, Roth LM, Brescia RJ, Zaloudek CJ, Cohen C: Immunohistochemical phenotype of ovarian granulosa cell tumors: Absence of epithelial membrane antigen has diagnostic value. Hum Pathol 25:60 – 66, 1994
CASE REPORT Signet Ring Stromal Tumor of the Ovary Occurring in Conjunction with Brenner Tumor 1 Alan W. Cashell, M.D.,* ,2 W. Gray Jerome, Ph.D.,† and Ernest Flores, M.D.* *Davis Memorial Hospital, Elkins, West Virginia 26241; and †Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157 Received October 11, 1999
Objective. A case is presented of a single ovarian mass that had elements of both signet ring stromal tumor of the ovary and Brenner tumor. Methods. The histologic features and the results of histocytochemical, immunohistochemical, and electron microscopic studies are presented. Results. The signet ring component of the mass demonstrated features consistent with the few other cases previously reported. A positive immunohistochemical stain for the peptide hormone inhibin provides additional evidence for an ovarian stromal origin for this tumor. Conclusion. The tumor produced no hormonally related symptoms and has shown no evidence of recurrence. Signet ring stromal tumor of the ovary is an uncommon benign tumor that may be confused with metastatic signet ring carcinoma. The significance of the signet ring cells is not certain. Their association with Brenner tumor has not been previously described. © 2000 Academic Press
Key Words: ovary; tumor; stromal; signet ring; Brenner tumor.
INTRODUCTION In 1976, Ramzy reported a previously undescribed primary ovarian neoplasm [1]. The tumor cells were highly vacuolated, resulting in what he perceived as a “signet-ring” appearance, similar to that commonly associated with Kru¨kenberg tumors. Histochemical and electron microscopic studies suggested a derivation from ovarian stromal cells. Four cases have since been described by Dickersin et al. [2] and one by Suarez et al. [3]. These tumors are benign and, from the established literature, appear to be quite rare. We report a signet ring stromal tumor of the ovary in association with an otherwise typical Brenner tumor. This neoplastic combination has not been previously reported. We 1
This work received financial support from Davis Memorial Hospital, Elkins, West Virginia. 2 To whom correspondence should be addressed. Fax: (304) 637-3527. E-mail: [email protected].
present histochemical, immunohistochemical, and ultrastructural studies of the signet ring elements, including an immunoperoxidase stain for the peptide hormone, inhibin. CASE REPORT A 52-year-old woman being seen for a routine yearly examination complained of unexplainable weight loss. Her past history was remarkable for a gunshot wound to the head in her teenage years. The physical examination revealed a cachectic appearance and long-standing neurologic and musculoskeletal deficits secondary to her previous injury. A pelvic examination revealed a left-sided adnexal mass. There was no pain or distention of the abdomen. A pelvic ultrasound and CT scan were performed, confirming a 7-cm left-sided mass suspicious for cancer. There was no clinical evidence of abnormal hormonal effect. A CA-125 level was within normal limits. The patient subsequently underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy and recovered without incident. MATERIALS AND METHODS Hematoxylin and eosin, periodic acid–Schiff (PAS), reticulin, and mucicarmine stains were performed on the ovarian mass after paraffin embedding. The reticulin stain was done by the method of Gridley. An immunoperoxidase stain for inhibin A was done using an antibody from Serotec Ltd. A mixedweight cytokeratin stain was done using a mixture of BioGenex AE1 and AE3 in a 1:40 dilution. Immunoperoxidase stains for smooth muscle actin, carcinoembryonic antigen (CEA), desmin, epithelial membrane antigen (EMA), and vimentin were performed using antibodies from BioGenex. An S-100 stain was done using an antibody from Dako. The CAM 5.2 antibody was purchased from Becton–Dickinson. For electron microscopy, the tissue containing the region of interest was removed from paraffin wax by overnight immersion in xylene. The deparaffinized tissue was rehydrated by
323
0090-8258/00 $35.00 Copyright © 2000 by Academic Press All rights of reproduction in any form reserved.
324
CASHELL, JEROME, AND FLORES
sequential incubation with a series of fluids containing decreasing percentages of ethanol (100% ethanol, 90% ethanol in distilled water, 75% ethanol, etc.). The tissue was then incubated in phosphate buffer, osmicated in 1% osmium tetroxide in phosphate buffer, dehydrated in a graded series of ethanol (increasing ethanol percentage), and embedded in epoxy resin. Following embedding, thick sections (0.5 m) were cut and then stained with toluidine blue to confirm the presence of signet ring cells. Following thin sectioning (80 nm) the tissue was viewed by electron microscopy at 80 keV. The volume of vacuoles as a percentage of cellular volume was determined by standard point count stereology [4]. PATHOLOGY With the adnexa removed, the uterus weighed 59 g and was unremarkable with a weakly proliferative endometrium. The right ovary had a tan surface and measured 2.4 ⫻ 1.2 ⫻ 0.7 cm. It was microscopically unremarkable with no evidence of neoplasia. The left ovary also had a tan lobulated surface and measured 5.5 ⫻ 2.4 ⫻ 1.4 cm. A thin-walled fluid-filled epithelial cyst measuring 6 cm in diameter was attached. Sectioning the ovary revealed a hard well-defined nodule with a firm mottled yellow to tan cut surface within the ovary and measuring up to 2.5 cm in diameter. Histologic examination of this mass revealed a circumscribed but unencapsulated tumor surrounded by a rim of postmenopausal ovarian stroma of varying thickness. Within the tumor were multiple vaguely circumscribed irregularly shaped areas of vacuolated cells occupying 20% of the mass (Fig. 1). Most of these cells contained a cytoplasmic vacuole large enough to displace the nucleus, creating a signet ring appearance. The nuclei had a slightly irregular contour, an open chromatin pattern, and single small nucleoli. They varied only slightly in size. No mitotic figures were seen. The remainder of the tumor was composed of a fibrous stroma with embedded nests of a Brenner (transitional cell) tumor. The epithelial nests of the Brenner tumor had no consistent spatial relationship to the signet ring cells but sometimes appeared nearby (Fig. 2). Some of the epithelial nests showed glandular structures. The Brenner nests were diffusely positive using a PAS reaction and focally positive with a mucicarmine stain. The signet ring cells showed a negative reaction for both stains. A reticulin stain showed a delicate network of fibers investing the signet ring cells as well as the surrounding fibrous stromal cells (Fig. 3). An immunoperoxidase stain for inhibin showed positive areas of staining within the majority of signet ring cells and in approximately half of the remaining stromal cells. The signet ring cells and the tumor stromal cells showed a diffuse positive reaction with the vimentin and actin stains. The signet ring cells demonstrated a negative staining reaction with mixed-weight cytokeratin, CAM 5.2, EMA, CEA, desmin, and S-100. The signet ring cell reactions to immunoperoxidase staining are summarized in Table 1.
Electron microscopy revealed a loose arrangement of cells interspersed between areas of collagen. The cells showed no evidence of basement membrane formation and junctional specializations between cells were not observed. Most of the cells had at least one to several large, clear vacuoles (Fig. 4). In some cells they occupied as much as 70% of the cross-sectional area and stereologic volume measurement revealed that they averaged 48% of the cell volume. Cytoplasm surrounding the vacuoles was often thin except in areas around the nucleus. Many smaller vacuoles were also present, giving a foamy appearance peripheral to the large vacuole. The origin of the majority of the vacuoles was not specifically determined, but most were surrounded by a single membrane. A few were formed by swollen mitochondria probably representing degenerative change. Some reticulin fibers were seen surrounding the cells consistent with the positive cytochemical stain. A few clusters of fibrillary material seen within the cells suggested phagocytosis. The nuclei were euchromatic with very little heterochromatin. Most showed only indistinct nucleoli. Many nuclei were indented. The cytoplasm contained abundant free ribosomes and moderately abundant endoplasmic reticulum (Fig. 5). Some of the latter had enlarged luminal diameters. In contrast, there were only modest numbers of mitochondria and a mature Golgi apparatus was observed only infrequently. DISCUSSION The signet ring stromal tumor of the ovary described by Ramzy is important to recognize because of its possible confusion with a metastatic Kru¨kenberg tumor [1]. Both of these entities are composed of cells largely filled by vacuoles. The signet ring stromal tumor, however, lacks the mitotic activity, the pleomorphism, and the hyperchromatic nuclei of Kru¨kenberg tumors. The origin of the tumor reported in this case from the ovarian stroma is supported by the positive immunohistochemical reaction to an inhibin antibody. Inhibin is a peptide hormone produced by ovarian granulosa and luteinized cells that prevents the release of follicle-stimulating hormone from the pituitary gland [5]. It is composed of ␣ and  subunits linked by disulfide bonds [5]. Antibodies to the ␣ chain have been used with immunohistochemical techniques to assist in the identification of ovarian granulosa cell tumors and other sex cord stromal tumors [5, 6, 7]. The negative chemical reactions of the signet ring cells for PAS and mucicarmine and the negative immunohistochemical reactions to mixed-weight cytokeratin, CAM 5.2, and EMA are strong evidence against a metastatic origin. The negative S-100, CEA, and desmin stains and the positive vimentin stain are consistent with previously reported cases [2, 3]. The positive smooth muscle actin was unexpected. However, a focal positive reaction for this antibody within a few signet ring cells was reported by Dickersin et al. in one of their series of four cases [2]. The study of Costa et al. [5] provides additional
FIG. 2.
FIG. 1. H&E-stained section showing one of the irregularly contoured clusters of signet ring cells, ⫻400. H&E-stained section showing the relationship of an epithelial Brenner tumor nest to nearby signet ring cells, ⫻400. FIG. 3. Reticulin stain shows fibers surrounding individual signet ring cells, ⫻400.
326
CASHELL, JEROME, AND FLORES
TABLE 1 Immunoperoxidase Stain Results for Signet Ring Cells Actin CAM 5.2 CEA Desmin EMA Inhibin Mixed-weight cytokeratin S-100 Vimetin
⫹ ⫺ ⫺ ⫺ ⫺ ⫹ ⫺ ⫺ ⫹
evidence that the positive smooth muscle actin stain complements the inhibin stain result in supporting the stromal origin of the signet ring cells in our case. In their study, a positive smooth muscle actin stain was seen in more than 90% of their series of 52 granulosa cell tumors [8]. The reticulin fiber investment of individual signet ring cells is also consistent with previously published cases [2, 3]. Ultrastructurally, our tumor shared the many free ribosomes and endoplasmic reticulum of Ramzy’s description [1]. However, many of the nuclei of our tumor were deeply indented in contrast to those previously described. It is not known whether the signet ring cells represent a true neoplasm or a reactive change. The four cases reported by Dickersin et al. had evidence of different origins including one with ultrastructural and immunohistochemical features of an epithelial tumor [2]. The irregular geographic distribution of signet ring cells within an otherwise typical Brenner tumor and their histochemical and immunohistochemical evidence of
FIG. 5. Transmission electron micrograph. This cell has multiple large vacuoles (V) in the cytoplasm. In addition, the lumens of much of the rough endoplasmic reticulum are swollen (arrowheads). ⫻12,150; bar ⫽ 0.5 m.
stromal origin suggest that this may be a reactive process. The tumor has shown no evidence of recurrence in the 2 years following excision. ACKNOWLEDGMENTS The authors thank Dr. Stamatakos and Dr. Tavassoli of the Armed Forces Institute of Pathology for reviewing the slides of this case. We also thank Dr. Jeffrey Stead and the histology staff of West Virginia University for performing the inhibin stain and Martha Ward of North Carolina Baptist Hospital for performing the CAM 5.2 stain. Marc Bleigh of Davis Memorial Hospital did the remaining stains.
REFERENCES
FIG. 4. Transmission electron micrograph. A signet ring cell has a very open nucleus with only minimal heterochromatin visible (arrowheads). Several very large vacuoles (V) and a number of smaller vacuoles are prominent in the cytoplasm. ⫻9800; bar ⫽ 1 m.
1. Ramzy I: Signet-ring stromal tumor of ovary. Cancer 38:166 –172, 1976 2. Dickersin GR, Young RH, Scully RE: Signet-ring stromal and related tumors of the ovary. Ultrastruct Pathol 19:401– 419, 1995 3. Suarez A, Palacios J, Burgos E, Gamallo C: Signet-ring stromal tumor of the ovary: A histochemical, immunohistochemical and ultrastructural study. Virchow’s Arch A Pathol Anat 422:333–336, 1993 4. Weibel ER: Stereological Methods. Vol. 1: Practical Methods for Biological Morphometry, San Diego, CA, Academic Press, 1979 5. Costa MJ, Ames PF, Walls J, Roth LM: Inhibin immunohistochemistry applied to ovarian neoplasms: A novel, effective, diagnostic tool. Hum Pathol 28:1247–1254, 1997 6. Zheng W, Sung CJ, Hanna I, DePetris G, Lambert-Messerlian G, Steinhoff M, Lauchlan SC: ␣ and  subunits of inhibin/activin as sex cord–stromal differentiation markers. Int J Gynecol Pathol 16:263–271, 1997 7. Flemming P, Wellmann A, Maschek H, Lang H, Georgii A: Monoclonal antibodies against inhibin represent key markers of adult granulosa cell tumors of the ovary even in their metastases. Am J Surg Pathol 19:927– 933, 1995 8. Costa MJ, DeRose PB, Roth LM, Brescia RJ, Zaloudek CJ, Cohen C: Immunohistochemical phenotype of ovarian granulosa cell tumors: Absence of epithelial membrane antigen has diagnostic value. Hum Pathol 25:60 – 66, 1994