Immunohistochemical distinction of endometrial stromal sarcoma and cellular leiomyoma

Immunohistochemical analysis of 147 cases of low-grade endometrial stromal sarcoma: refining the immunohistochemical profile of LG-ESS on a large, molecularly confirmed series

Low-grade endometrial stromal sarcoma (LG-ESS) can present diagnostic challenges, due to its overlapping morphological features with other uterine mesenchymal tumors. Misdiagnosis rates remain significant, and immunohistochemical data for LG-ESS are limited to small series and inconsistent antibody panels. This study aimed to refine the IHC profile of LG-ESS by analyzing a large, molecularly confirmed series of 147 cases using a panel of 24 antibodies, including newer markers like transgelin and smoothelin. CD10 and IFITM1, key endometrial stromal markers, were expressed in 86% (92% of those extensively) and 69% (60% of those extensively) of cases, with fusion-positive tumors showing significantly higher expression. Smooth muscle markers (α-SMA, desmin, h-caldesmon, calponin, transgelin) were variably expressed, predominantly in focal or low-intensity patterns, with α-SMA reaching the highest frequency of expression (44%). However, the intensity of smooth muscle marker expression was usually very low. Smoothelin was rarely expressed. Hormone receptors were frequently positive, with PR showing a higher frequency (92% vs. 83%) and intensity than ER. Markers like S-100, HMB45, and CD117 were largely negative; all tumors were p53 wild-type, with preserved SMARCB1/SMARCA4 expression and ALK and ROS1 negativity. This work represents the largest molecularly validated IHC study on LG-ESS, providing a robust diagnostic profile for routine pathology. By addressing key diagnostic limitations and examining newer markers, our study supports a more standardized approach to diagnosing LG-ESS and underscores the value of immunohistochemical panels, particularly in fusion-negative tumors where diagnosis relies on morphological and immunohistochemical interpretation. These findings contribute critical data for improving diagnostic accuracy.

Smooth Muscle Myosin Heavy Chain Expression in Nodal and Extranodal Follicular Dendritic Cell Sarcoma

Follicular dendritic cell sarcoma (FDCS) is a rare neoplasm requiring a high index of suspicion, especially on small biopsies. Smooth muscle myosin heavy chain (SMMHC) is a common immunohistochemical (IHC) stain that has been reported to mark normal nodal follicular dendritic cells (FDCs). We hypothesize that SMMHC can be a sensitive marker for FDCS and aim to compare its performance with established markers of FDCS. The archive of a large academic center was searched for cases of FDCS. Clinical features, including age, sex, and site at diagnosis, were reviewed. A hematoxylin and eosin-stained slide was evaluated to assess for morphology and presence of hyaline vascular Castleman disease. The established FDC markers CD21, CD23, fascin, clusterin, and D2-40 were reviewed and compared with SMMHC for all cases. The staining pattern was classified as positive (strong or weak) or negative. Seven unique cases of nodal and extranodal FDCS were collected. SMMHC was positive in most cases (n=5) and performed similarly to established FDC markers, including clusterin, CD21, and CD23 (n=7 each), and fascin and D2-40 (n=4 each). SMMHC was also negative in all 14 examined cases among 5 common differential diagnoses. We demonstrate that the common IHC marker SMMHC has high specificity and similar sensitivity as established FDC markers in nodal and extranodal FDCS, and is useful in the evaluation of common neoplastic mimics.

Uterine Smooth Muscle Tumors: An Overview

Uterine smooth muscle tumors are a heterogeneous group of mesenchymal neoplasms with multiple histologic variants and distinct biological behaviors. Pathologic classification (benign, uncertain malignant potential, malignant) relies on the evaluation of mitotic index, necrosis, and degree of cytologic atypia, with different thresholds based on each subtype. Immunohistochemistry and other ancillary studies may be necessary to establish the diagnosis in a subset of cases, given the morphologic overlap with other mesenchymal neoplasms, including low-grade and high-grade endometrial stromal tumors, inflammatory myofibroblastic tumors, and PEComa. Recent advances in molecular diagnostics have refined the classification of smooth muscle tumors, but most cases are diagnosed purely on histologic grounds.

Cell type-specific expression of estrogen and progesterone receptors in the human vaginal mucosa

Female sex hormones affect the immune response in the lower female genital tract. To understand their mechanisms of action, it is essential to define cell types expressing estrogen receptor (ER) and/or progesterone receptor (PR) in the human vaginal mucosa (VM). Here, we report that none of the dendritic cell (DC) subsets in the human VM expressed ERα or PR in situ. However, they were capable of expressing ERα, but not PR, after in vitro culture of the whole VM tissues. Similarly, ERα and/or PR expression by T cells in the VM tissues was also inducible rather than constitutive. In contrast, ERα and/or PR were constitutively expressed in HLA-DR^- non-immune cell types (vimentin⁺, desmin⁺, or CD10⁺). These new findings will help us understand the mechanisms of action of female sex hormones in the modulation of immune response in the human VM and lower female genital tract.

Uterine cellular leiomyomas are characterized by common HMGA2 aberrations, followed by chromosome 1p deletion and MED12 mutation: morphological, molecular, and immunohistochemical study of 52 cases

Cellular leiomyoma (CL) represents an uncommon variant of uterine leiomyoma with limited data concerning its immunohistochemical and molecular profile. We performed a comprehensive analysis of 52 CL cases all of which were analyzed immunohistochemically. Molecular analysis was possible in 32 cases with sufficient DNA, and 38 cases with sufficient RNA. The immunohistochemical results showed a high expression of smooth muscle markers (calponin (100%), desmin (100%), smooth muscle actin (98.1%), caldesmon (96.1%), transgelin (96.1%), smooth muscle myosin heavy chain (86.5%), and smoothelin (61.5%)). Concerning markers of endometrial stromal differentiation, the expression of CD10 was observed in 65.4% cases (42.2% with H-score > 50), and IFITM1 in 36.5% cases (1.9% with H-score > 50). 36.5% showed HMGA2 overexpression at the IHC level, associated with increased mRNA expression in 14/14 cases. The rearrangement of the HMGA2 gene was detected in 13.2%. Chromosome 1p deletion was found in 19.3%, while 9.4% of tumors showed a pathogenic mutation in the MED12 gene. In conclusion, CL is immunohistochemically characterized by a high expression of "smooth muscle" markers commonly associated with a co-expression of "endometrial stromal" markers, where IFITM1 shows superior performance compared to CD10 regarding its specificity for differentiation from endometrial stromal tumors. The sensitivity of smoothelin in CL seems rather low, but no data is available to assess its specificity. On a molecular level, the most common mutually exclusive aberration in CL affects HMGA2, followed by chromosome 1p deletions and MED12 mutations.

P16, Ki67, P53, and WT1 Expression in Uterine Smooth Muscle Tumors: An Adjunct in Confirming the Diagnosis of Malignancy in Ambiguous Cases

The diagnosis of uterine smooth muscle tumors is sometimes difficult, as these tumors may show worrisome features, suspicious for but not diagnostic of malignancy. The recommended immunohistochemical panel in this setting is currently under debate. In this study, we aimed to find a panel of immunohistochemical stains that would be helpful in determining the correct diagnosis in ambiguous uterine smooth muscle tumors, with an emphasis on investigating the possible usefulness of the WT1 antibody. Uterine leiomyomas were found to be immunoreactive with WT1. Since a previous study reported on the lack of immunoreactivity of uterine leiomyosarcomas with WT1, we speculated that WT1 might be useful in this setting. We retrospectively reviewed the medical charts and slides of 91 patients: 22 with leiomyosarcoma, 15 with smooth muscle tumor of uncertain malignant potential, and 54 with leiomyoma. Immunohistochemical stains for WT1, p16, p53, and Ki67 were performed on each case. We found that immunoreactivity with p16 and Ki67 (>40% and >10% of the tumor cells, respectively) and loss of nuclear expression of WT1 (<10% of the tumor cells) were significantly more common in leiomyosarcomas (all P<0.001). Mutated p53 immunohistochemical staining pattern was significantly more prevalent in leiomyosarcomas than in leiomyomas (P<0.001). Thus, in diagnostically challenging uterine smooth muscle tumors, we recommend using an immunohistochemical panel composed of Ki67, p16, p53, and WT1. A positive result in either of the former 2 (p16 >40% and/or Ki67 >10%) has the strongest association with leiomyosarcoma (sensitivity: 95.5%, specificity=88.9%, positive predictive value=77.8%, negative predictive value=98.0%).

Endometrial stromal sarcoma: A review of rare mesenchymal uterine neoplasm

OBJECTIVE

This review aims to analyze the pathological aspects, diagnosis and treatment of rare mesenchymal uterine tumors.

METHODS

On August 2019, a systematic review of the literature was done on Pubmed, MEDLINE, Scopus, and Google Scholar search engines. The systematic review was carried out in agreement with the Preferred Reporting Items for Systematic Reviews and Meta-Analyzes statement (PRISMA). The following words and key phrases have been searched: "endometrial stromal sarcoma", "low-grade endometrial stromal sarcoma", "high-grade endometrial stromal sarcoma", "uterine sarcoma", "mesenchymal uterine tumors" and "uterine stromal sarcoma". Across these platforms and research studies, five main aspects were analyzed: the biological characteristics of the neoplasms, the number of cases, the different therapeutic approaches used, the follow-up and the oncological outcomes.

RESULTS

Of the 94 studies initially identified, 55 were chosen selecting articles focusing on endometrial stromal sarcoma. Of these fifty-five studies, 46 were retrospective in design, 7 were reviews and 2 randomized phases III trials.

CONCLUSION

Endometrial stromal sarcomas are rare mesenchymal uterine neoplasms and surgery represents the standard treatment. For uterus-limited disease, the remove en bloc with an intact resection of the tumor (without the use of morcellation) is strongly recommended. For advanced-stage disease, the standard surgical treatment is adequate cytoreduction with metastatectomy. Pelvic and para-aortic lymphadenectomy is not recommended in patients with Low-grade Endometrial Stromal Sarcoma (ESS), while is not clear whether cytoreduction of advanced tumors improves patient survival in High-grade ESS. Administration of adjuvant radiotherapy or chemotherapy is not routinely used and its role is still debated.

Gene fusions characterize a subset of uterine cellular leiomyomas

Uterine leiomyomas are the most common benign tumor of the female genital tract. Previous studies have shown that conventional leiomyomas often harbor-specific alterations including rearrangements involving HMGA2. Cellular leiomyomas are a variant of uterine leiomyoma that are less well-studied from a genomic point of view. Morphologically and immunohistochemically, cellular leiomyomas may be confused with low-grade endometrial stromal neoplasms, a group of tumors which frequently harbor a number of recurrent gene fusions. Ancillary molecular testing may be used to investigate tumors where low-grade endometrial stromal neoplasms enter into the differential diagnosis. At our institution, we identified a uterine cellular leiomyoma harboring a HMGA2-TRAF3IP2 fusion. After a retrospective review 11 additional tumors were identified. All included cases were reviewed and evaluated for immunohistochemical expression of smooth muscle actin, desmin, h-caldesmon, CD10, estrogen receptor, and progesterone receptor. RNA sequencing using the TruSight RNA Fusion Panel was performed on formalin-fixed paraffin-embedded tissue samples. In addition to the index case, two other cases harbored fusions: HMGA2-NAA11 and TPCN2-YAP1, of which the latter is novel and was confirmed with reverse transcriptase-polymerase chain reaction. In conclusion, a subset of cellular leiomyomas harbor rearrangements involving HMGA2, suggesting molecular kinship with conventional uterine leiomyomas. In addition, the prevalence of the novel TPCN2-YAP1 gene fusion in cellular leiomyomas requires further study. The fusions reported here, when identified, may be useful when the diagnosis of cellular leiomyoma is in question.

Beyond Smooth Muscle-Other Mesenchymal Neoplasms of the Uterus

Mesenchymal tumors of the uterus comprise a heterogeneous group of neoplasms of varied biologic potential. In addition to being host to several anatomically unique entities, the uterus may contain mesenchymal neoplasms typically found elsewhere in the body. Although smooth muscle neoplasms are common, other mesenchymal neoplasms in this location are relatively rare. Many of these neoplasms exhibit morphologic overlap. In addition to a careful histomorphologic review, definitive classification frequently depends on the judicious application of ancillary immunohistochemical and molecular testing. The intent of this review is to offer a basic approach to the classification of primary uterine mesenchymal neoplasms.

Use of Smooth Muscle Myosin Heavy Chain as an Effective Marker of Follicular Dendritic Cells

Smooth muscle myosin heavy chain (SMMHC) is a major structural component of the contractile apparatus in smooth muscle cells. Even though it is considered a relatively specific marker for terminal smooth muscle cell differentiation, expression in other cell types such as follicular dendritic cells (FDCs) has rarely been reported. To determine whether SMMHC represents an effective FDC marker in lymphoid tissues, we compared the immunohistochemical results for SMMHC with those of the traditional FDC markers podoplanin (D2-40) and CD21. Paraffin sections of 44 lymphoid tissues were analyzed, including 31 cases of follicular hyperplasia, 6 cases of follicular lymphoma, 2 cases of peripheral T-cell lymphoma, 3 cases of diffuse large B-cell lymphoma arising in follicular lymphoma, 1 case of nodular sclerosis classical Hodgkin lymphoma, and 1 case of small lymphocytic lymphoma. There was no statistically significant difference between the number of SMMHC-positive and D2-40-positive or CD21 lymph nodes (P>0.05). The extent and intensity of SMMHC-positive FDCs were similar to those of D2-40-positive FDCs (P=0.127 and 0.733, respectively), but significantly lower compared with those of CD21 cells (P=0.009 and 0.00002, respectively). However, in contrast to CD21 which was also positive in some germinal center B cells, SMMHC expression was restricted to FDCs. Our results indicate that SMMHC is an excellent marker for FDCs and can be particularly helpful in demonstrating the underlying architecture in lymphoid processes.

Clinicopathological characteristics and treatment strategies for patients with low-grade endometrial stromal sarcoma

To investigate and evaluate the clinicopathological characteristics and treatment strategies for patients with low-grade endometrial stromal sarcoma (LG-ESS).The medical records of LG-ESS patients who were treated at 2 cancer referral centers from January 2005 to December 2015 were retrospectively reviewed.Twenty patients with LG-ESS met the inclusion criteria and were included in this analysis. Hysterectomy with bilateral salpingo-oophorectomy was the mainstay of surgery. Lymphadenectomy was performed in 12 (60%) cases, and no positive nodes were identified. CD10 was the most commonly used immunohistochemistry marker, followed by smooth muscle actin (SMA), estrogen receptor (ER), desmin, progesterone receptor (PR), and S-100; the positivity rates of these markers were 88.2%, 66.7%, 75.0%, 16.7%, 88.9%, and 0, respectively. Postoperative chemotherapy, radiotherapy, and hormonal treatment were provided alone or in combination in 10 (50%) patients, 4 (20%) patients, and 1 (5%) patient, respectively. One patient developed lung metastasis at initial diagnosis, and 2 (10%) patients had recurrence with distant metastasis. They all underwent complete or incomplete resection followed by hormonal treatment. The overall survival time of these patients was 66, 89, and 109 months at last contact, respectively. The 5-year and 10-year disease-free survival rates for the entire cohort were 90% and 72%, respectively. No patients died of the disease.CD10/SMA/ER/PR in combination with desmin/S-100 might improve the diagnostic accuracy. Surgical resection is the foremost treatment for LG-ESS patients with recurrence or distant metastasis. Hormonal treatment may be beneficial for unresectable or residual tumors.

Immunohistochemical panel to differentiate endometrial stromal sarcoma, uterine leiomyosarcoma and leiomyoma: something old and something new

AIMS

To evaluate an immunohistochemical panel differentiating endometrial stromal sarcoma (ESS) from uterine leiomyosarcoma (ULMS) and leiomyoma (LM).

METHODS

94 cases (28 ESS, 41 ULMS, 25 LM) were retrieved and arrayed. 10 immunomarkers (estrogen receptor (ER), progesterone receptor (PR), CD10, smooth muscle actin, desmin, h-caldesmon, transgelin, GEM, ASC1, stathmin1) were used. A predictive model was constructed and examined by receiver operating characteristics curve analysis to determine area under the curve (AUC).

RESULTS

The combination of ER(+)/PR(+)/CD10(+)/GEM(-)/h-caldesmon(-)/transgelin(-) can predict ESS versus ULMS with AUC predictive value of 0.872 (95% CI 0.784 to 0.961, p<0.0001). The combination of ER(+)/PR(+)/CD10(+)/h-caldesmon(-)/transgelin(-) can predict low grade (LG) ESS from 'LG' ULMS with AUC predictive value of 0.914 (95% CI 0.832 to 0.995, p<0.0001). Finally, ULMS and ESS, including the LGs, were more likely to be stathmin1(+) than LM.

CONCLUSIONS

Due to the different clinical course and management, adding novel antibodies (GEM, transgelin) to the well established immunohistochemistry panel seemed to be useful in distinguishing ESS from ULMS and LG ESS from 'LG' ULMS. Finally, stathmin1 expression could be of value in differentiating LM from uterine sarcomas.

Cellular leiomyoma with necrosis and mucinous degeneration presenting as pseudo-Meigs' syndrome with elevated CA125

Pseudo-Meigs' syndrome is a syndrome rarely caused by leiomyomas. Elevated CA125 usually suggests malignancy of the ovary. No reported case of pseudo-Meigs' syndrome presenting with necrosis and mucinous degeneration of uterine cellular leiomyomas (CLs) and an elevated CA125 level was found upon a PubMed search. A 37-year-old woman presenting with massive ascites, bilateral pleural effusions and a pelvic mass measuring 20 x 18 x 10 cm is described. The pre-operative serum CA125 was 920.4 U/ml. After total abdominal hysterectomy and partial omentumectomy, the final pathologic diagnosis was CL with focal hemorrhage, necrosis and mucinous degeneration. The ascites and pleural effusion disappeared, and the CA125 level returned to normal in one month. Benign leiomyoma accompanied by pseudo-Meigs' syndrome and elevated serum CA125 can mimic a pelvic malignancy.

Endometrial stromal tumours revisited: an update based on the 2014 WHO classification

Endometrial stromal tumours (EST) are rare tumours of endometrial stromal origin that account for less than 2% of all uterine tumours. Recent cytogenetic and molecular advances in this area have improved our understanding of ESTs and helped refine their classification into more meaningful categories. Accordingly, the newly released 2014 WHO classification system recognises four categories: endometrial stromal nodule (ESN), low-grade endometrial stromal sarcoma (LGESS), high-grade endometrial stromal sarcoma (HGESS) and undifferentiated uterine sarcoma (UUS). At the molecular level, these tumours may demonstrate a relatively simple karyotype with a defining chromosomal rearrangement (as in the majority of ESNs, LGESSs and YWHAE-rearranged HGESS) or demonstrate complex cytogenetic aberrations lacking specific rearrangements (as in UUSs). Herein we provide an update on this topic aimed at the practicing pathologist.

Clinicopathological and molecular markers associated with prognosis and treatment effectiveness of endometrial stromal sarcoma: a retrospective study in China

Purpose

To evaluate the clinicopathological and immunophenotypic characteristics of endometrial stromal sarcoma (ESS) in China.

Methods and materials

Seventy-two consecutive ESS cases treated between 1995 and 2009 were retrospectively reviewed.

Results

Sixty-three patients received surgical treatment. Forty-one patients underwent pelvic lymphadenectomy. In paraffin-embedded specimens, expression of the following molecular markers was detected: CD10 (27/36), vimentin (37/38), HHF35 (3/32), S-100 (0/25), desmin (2/29), CD117 (0/23), CD34 (2/24), alpha-inhibin (0/17), CK (1/34), CD99 (4/9), smooth muscle actin (5/25), EMA (0/7), estrogen receptor (13/16) and progesterone receptor (13/16). CD10 and vimentin were expressed more frequently in these specimens. Tumor classification, CD10 and surgical procedures were significantly associated with disease-free survival (DFS). Surgical procedures were significantly associated with overall survival (OS). Tumor stage (P = 0.024) and surgical procedure (P = 0.042) were found to be significant independent prognostic factors for DFS. No complete or partial response was observed among patients who received radiotherapy or chemotherapy.

Conclusions

Our results indicate that total hysterectomy with bilateral salpingo-oophorectomy followed by pelvic lymphadenectomy is associated with an improved treatment outcome. CD10-negative expression may contribute to the malignant characteristics and recurrence associated with ESS.

Adenomyomatous Polyp of the Endometrium With Prominent Epithelioid Smooth Muscle Differentiation

A minor component of smooth muscle may be present in the stroma of benign endometrial polyps and 2 distinctive endometrial polypoid lesions, atypical polypoid adenomyoma and adenomyoma, are characterized by stroma with a predominant smooth muscle component. In this report, we describe 2 unusual endometrial polyps in 43- and 60-year-old women in which the stromal component was predominantly composed of smooth muscle with an epithelioid appearance, a phenomenon which, as far as we are aware, has not been previously reported.

Endometrial stromal tumors: immunohistochemical and molecular analysis of potential targets of tyrosine kinase inhibitors

BACKGROUND

The systemic treatment of malignant endometrial stromal tumors (EST) is not well established. A few reports describe objective responses to imatinib, which suggest a novel therapeutic strategy for these tumors. Due to these facts, we aimed to perform a retrospective analysis of possible molecular targets of tyrosine kinase inhibitors (TKI) in EST: KIT, PDGFRA and EGFR.

METHODS

52 endometrial stromal sarcomas and 13 undifferentiated endometrial sarcomas were examined and reviewed. Mutational analysis were performed for exons 9, 11, 13, and 17 of the KIT gene, exons 12 and 18 of the PDGFRA gene and exons 18, 19, 20 and 21 of the EGFR gene. The incidence and distribution of the KIT, PDGFRA, and EGFR expression were examined by immunohistochemistry, and EGFR amplification was assessed by fluorescence in situ hybridization.

RESULTS

No mutations in KIT, PDGFRA and EGFR genes were detected. Overexpression of KIT, PDGFRA, EGFR, was detected in 2 (3%), 23 (35.4%), 7 (10.8%) cases respectively, whereas amplification of EGFR gene was not found.

CONCLUSIONS

Absence of significant expression, amplification and activating mutations on these tyrosine kinase receptors suggest that it is unlikely that EST can benefit from therapies such as TKI on the systemic setting.

Endometrial stromal sarcoma: A review of the literature

Endometrial stromal sarcomas are rare malignant tumors of the uterus, and most of the information available in literature is based on small series or case reports. A proper preoperative diagnosis is difficult and in most cases the diagnosis is confirmed after hysterectomy for a presumed benign disease. Endometrial sampling, ultrasound, and magnetic resonance imaging can provide diagnostic clues. Total hysterectomy with bilateral salpingo-oopherectomy is the main line of management and for early disease complete cure is a reality. Ovarian conservation may be possible in young women with early stage disease and the role of lymphadenectomy is controversial. Adjuvant hormone therapy in the form of progesterone, gonadotropin releasing hormone analogues, and aromatase inhibitors are found to be effective in preventing recurrences. Hormone therapy, radiotherapy and surgical excision of the metastasis are recommended for recurrences.

Low-Grade Endometrial Stromal Sarcoma and Undifferentiated Endometrial Sarcoma: A Comparative Analysis Emphasizing the Importance of Distinguishing Between These Two Groups

Endometrial stromal sarcomas (ESSs) are rare tumors whose classification is still controversial. In this study, the authors studied 19 patients diagnosed with ESS at the Hospital S João, Porto, Portugal; reviewed their files and material; and performed immunohistochemical study for CD10, desmin, and smooth muscle actin markers, aiming to compare low-grade endometrial stromal sarcomas (LG-ESSs) and undifferentiated endometrial sarcomas (UESs) using the World Health Organization (WHO) classification. Twelve cases (63%) were classified as LG-ESS and 7 (37%) as UES. The median age at diagnosis was 49 years, and women with LG-ESS tended to be younger than those with UES. Most cases (7/11) had a previous echographic diagnosis of leiomyoma. A biopsy or curettage was performed in 6 cases, providing a definitive diagnosis of malignancy in 4. Frozen section was performed in 4 patients. The majority (63%) of patients were FIGO stage I. Twelve (63%) cases showed diffuse or focal expression of CD10. Desmin and smooth muscle actin expression was focal in 4 (21%) tumors. Patients with LG-ESS had a significant better overall survival than those with UES ( P = .026). Mitotic count had no prognostic significance. Our data emphasize the clinical importance of the WHO classification in ESS. It is of utmost importance to establish a proper classification to increase the consistency of data that may be useful for improving clinical and therapeutic management of patients with ESS.

Calretinin: diagnostic utility in the female genital tract

The utility of calretinin was first described in the diagnosis of mesothelioma. In the female genital tract, calretinin was initially reported in Wolffian remnants and related lesions and later used in the diagnosis of sex cord stromal tumors of the ovary, endometrial stromal tumors with sex cord-like differentiation, and uterine tumors resembling sex cord tumors of the ovary. This review discusses calretinin expression in normal tissues of the female genital tract and highlights its potential utility in the diagnosis of these subsets of neoplasms with emphasis to tumors that may constitute a problem in their differential diagnosis. In particular, the limited utility of calretinin in the diagnosis of sex cord stromal tumors of the ovary, in the differential diagnosis between mesothelioma and serous tumors involving the ovary and/or peritoneum, and in the differential diagnosis between Wolffian lesions and endometrial carcinoma are addressed.

Mullerian adenosarcomas: an immunophenotypic analysis of 35 cases

Mullerian adenosarcomas (MAs) are rare mixed mesenchymal and epithelial neoplasms that occur most commonly in the uterus. Although the epithelial component is typically benign, the mesenchymal component of most adenosarcomas morphologically resembles that observed in endometrial stromal tumors and is responsible for their clinical behavior. Thus, the differential diagnosis usually includes not only low-grade endometrial stromal tumors, but also adenofibroma, carcinosarcoma, and embryonal rhabdomyosarcoma especially in small samples. The objective of this study was to ascertain the immunophenotypic profile of the epithelial and mesenchymal components of MAs and delineate possible differences between conventional mesenchymal areas and areas of sarcomatous overgrowth. Representative sections from 35 MAs, 28 of them without sarcomatous overgrowth (MA-NSO) and 7 with sarcomatous overgrowth (MA-SO), were included in the study. Thirty tumors arose in the uterus, 4 were pelvic, and 1 originated in the colon. Adequate blocks were selected and immunostained for estrogen receptor (ER), progesterone receptor (PR), androgen receptor (AR), CD10, WT1, smooth muscle actin, desmin, AE1/3 cytokeratin, CD34, calretinin, inhibin, c-kit, and Ki-67. The mesenchymal component expressed ER in 21/27 MA-NSOs but in only 1/7 MA-SOs (65% overall). PR was expressed in 21/26 MA-NSOs and 4/7 MA-SOs (76% overall), whereas AR was positive in 10/27 MA-NSOs and 5/7 MA-SOs (35% overall). CD10 was expressed in 23/28 MA-NSOs but in only 2/7 MA-SOs (71% overall), and WT1 positivity was seen in 22/27 MA-NSOs and 6/7 MA-SOs (79% overall). Sixty-seven percent of MAs expressed smooth muscle actin, 32% desmin, including both examples of MA-SOs with rhabdomyoblastic differentiation, and 25% expressed AE1/3 cytokeratin. CD34 expression was found in 35% of the tumors, but it was almost always patchy in distribution and weak in intensity, as was calretinin expression, seen only in 12% of the cases. Expression of c-kit and inhibin in greater than 5% of the tumor cells was not encountered. The median and mean Ki-67 labeling indices were 10% and 12%, respectively (range, <5% to 40%). The median and mean Ki-67 indices were both 5% in MA-NSOs compared with 30% and 28%, respectively, in MA-SOs. The epithelial compartment demonstrated expression for ER (24/32), PR (23/31), and AE1/3 cytokeratin (33/33); rare cases expressed CD10 (4 cases) and AR (1 case). In summary, the immunophenotype of most MAs resembled that of endometrial stromal tumors (positive for ER, PR, WT1, and CD10, with variable expression of muscle markers, AR and cytokeratin). The proliferative rate in the stromal component was strongly related to the presence of sarcomatous overgrowth. ER, PR, and CD10 expression was lost in MA-SOs relative to conventional low-grade stromal areas of mullerian/mesodermal adenosarcomas, reflecting the "dedifferentiation" of this component.

Expression of CD56 and WT1 in ovarian stroma and ovarian stromal tumors

The immunophenotype of ovarian stroma and spindle cell tumors derived from ovarian stroma has not been well studied. We studied the expression of CD56, WT1, estrogen receptor-beta (ER-beta), progesterone receptor (PR), smooth muscle actin, S-100, CD34, and muscle specific actin in 16 normal ovaries, 17 ovarian fibromas, 11 ovarian cellular fibromas, 10 ovarian fibrothecomas, and 11 ovarian leiomyomas. In addition, we studied CD56 and WT1 expression in 7 cases of normal endometrium, 8 uterine smooth muscle tumors, 5 endometrial stromal tumors and 64 nongynecologic (GYN) spindle cell sarcomas. All normal ovaries, ovarian fibromas, fibrothecomas, and ovarian leiomyomas were positive for CD56 and WT1. Most of the normal ovaries, ovarian fibromas, ovarian fibrothecomas, and ovarian leiomyomata also expressed ER-beta and PR. Eight of 17 ovarian fibromas, 5 of 11 ovarian cellular fibromas, and 4 of 10 ovarian fibrothecoma with focal fibroblastic differentiation were positive for smooth muscle actin. A few cases of these tumors also expressed S-100 and CD34. Only rare cases of non-GYN spindle cell sarcomas expressed WT1. Our study results show that ovarian fibromas, fibrothecomas, and leiomyomas have a similar immunophenotype (positive for CD56, WT1, ER-beta, and PR) to that of ovarian stromal cells, supporting an ovarian stromal origin for these neoplasms. However, unlike normal ovarian stromal cells, ovarian fibromas, fibrothecomas, and leiomyomas can also show fibroblastic, smooth muscle, Schwannian, and solitary fibrous tumorlike differentiation. WT1 is a fairly specific marker for spindle cell tumors of gynecologic organs, including ovarian spindle cell tumors, endometrial stromal tumors, and uterine smooth muscle tumors. Non-GYN spindle cell sarcomas rarely express WT1. CD56 is strongly expressed in ovarian stromal cells but not in endometrial stromal cells. CD56 is often expressed by a wide variety of spindle cell sarcomas, thus, it has no value in differentiating GYN from non-GYN spindle cell tumors.

Immunohistochemistry in Gynecologic Pathology

Although most diagnoses in gynecologic pathology are established through the examination of routine hematoxylin-eosin–stained slides, immunohistochemical studies can be of assistance in some cases. The following case studies are used to illustrate the value of some relatively new markers in the diagnosis of gynecologic neoplasms and to highlight potential diagnostic pitfalls.

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.

High Frequency of JAZF1-JJAZ1 Gene Fusion in Endometrial Stromal Tumors With Smooth Muscle Differentiation by Interphase FISH Detection

The most common cytogenetic alteration observed in low-grade endometrial stromal tumors (EST) is the t(7;17)(p15;q21) translocation, resulting in the fusion of the JAZF1 and JJAZ1 genes. By reverse-transcription polymerase chain reaction, the translocation has been detected overall in one-third of ESTs, but only rarely in its variants. The purpose of this study was to develop a fluorescence in situ hybridization assay for detection of this translocation using archival paraffin-embedded samples of ESTs with smooth muscle differentiation and to assess the nature of the smooth muscle component of these tumors. Representative paraffin blocks of 9 endometrial stromal nodules and 1 low-grade endometrial stromal sarcoma were collected for the study. In 1 case, the block selected also contained areas of sex cordlike differentiation. A fluorescence in situ hybridization probe set was designed to detect the t(7;17)(p15;q12) on tissue sections. Six out of 10 collected ESTs were assessable. Fusion signals were detected in 3 out of 6 cases (50%) in both the conventional endometrial stromal and the smooth muscle components of the tumors. The tumor sample with sex cordlike differentiation harbored the fusion signal in all the 3 components. Our results support the contention that the endometrial stromal and smooth muscle components of these tumors have the same origin, either from a common precursor cell with pluripotential differentiation or from endometrial stromal cells that have undergone smooth muscle metaplasia. Our results indicate that the detection of this chromosomal abnormality can be used to diagnose ESTs with smooth muscle differentiation when the smooth muscle component is predominant.

Differential expression of smooth muscle myosin, smooth muscle actin, h-caldesmon, and calponin in the diagnosis of myofibroblastic and smooth muscle lesions of skin and soft tissue

The diagnosis of low-grade and pseudosarcomatous spindle cell lesions of skin and soft tissue can sometimes be problematic; in particular, distinction between fibroblastic, myofibroblastic, and smooth muscle proliferations can occasionally pose difficulties on routine histologic examination. We have applied a panel of immunohistochemical markers to a series of spindle cell lesions of skin and soft tissue to assess the utility of the differential expression of smooth muscle and myofibroblastic-associated markers. Twenty-eight cases of nodular fasciitis, 42 cases of fibromatosis, and 3 cases of myofibroblastic sarcoma were stained with antibodies against smooth muscle actin (SMA), smooth muscle myosin (SMMS), calponin, and high-molecular weight caldesmon (h-caldesmon). For comparison, 12 cases of cutaneous leiomyoma and 8 cases of leiomyosarcomas involving superficial soft tissues and fascia were studied with the same panel of antibodies. Thirty-eight of 42 cases of fibromatosis were positive for SMA, 42/42 cases were positive for calponin, 39/42 cases were negative for SMMS, and all cases were negative for h-caldesmon. All cases of nodular fasciitis were positive for SMA and calponin, and all were negative for h-caldesmon and SMMS. All cases of myofibroblastic sarcoma were positive for SMA and 2/3 cases for calponin, and were negative for SMMS and h-caldesmon. All cases of cutaneous leiomyoma and leiomyosarcoma were positive for all 4 markers tested. Our results demonstrate a remarkably consistent pattern of reactivity of muscle and myofibroblastic-associated markers in lesions predominantly composed of myofibroblastic spindle cells, characterized by positive staining for SMA and calponin and absence of reactivity for SMMS and h-caldesmon. Application of this panel of stains may be of aid in the differential diagnosis of low-grade myofibroblastic lesions such as nodular fasciitis and fibromatosis from smooth muscle tumors of skin and soft tissue. This panel may additionally be of assistance in the diagnosis of myofibroblastic sarcoma.

CD10 is helpful in detecting occult or inconspicuous endometrial stromal cells in cases of presumptive endometriosis

BACKGROUND

Previous studies have shown that CD10 is a marker for normal, ectopic, and neoplastic endometrial stromal cells. However, its value in confirming a diagnosis of presumptive endometriosis has not been extensively studied.

OBJECTIVE

To assess the reactivity of CD10 in a series of cases of presumptive endometriosis and to establish the potential usefulness of this antibody in confirming the diagnosis.

DESIGN

We studied hematoxylin-eosin sections and immunoreactivity of CD10 in 20 cases diagnosed as "suspicious for," "suggestive of," or "compatible with" endometriosis as well as in 12 cases of lesions that may be confused with endometriosis (3 endosalpingioses, 3 mesothelial hyperplasias, 3 ovarian follicular cysts, and 3 hemorrhagic corpora lutea).

RESULTS

Routine sections from cases of presumptive endometriosis showed glands lacking a distinct cuff of endometrial stromal cells because of atrophy or because of changes secondary to hemorrhage, inflammation, fibrosis, and/or cystic dilatation. In a few cases, the distinction between endometrial and ovarian stroma could not be assessed with certainty. CD10 immunostaining confirmed the diagnosis in 17 (85%) of the cases, as it strongly stained endometrial stromal cells that were not apparent on hematoxylin-eosin sections. All sections from lesions that may simulate endometriosis were CD10-.

CONCLUSION

CD10 is helpful in detecting occult or inconspicuous ectopic endometrial stromal cells and in distinguishing endometriosis from its potential mimickers. We recommend its use to confirm or exclude the presence of endometrial stromal cells in cases of presumptive endometriosis and in lesions that may be mistaken for this entity.