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Year : 2021  |  Volume : 64  |  Issue : 2  |  Page : 310-315
Tissue microarray based immunohistochemical study of TLE1 in synovial sarcoma and its histologic mimics

1 Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad; Department of Pathology and Lab Medicine, All India Institute of Medical Sciences, Bibinagar, Telangana, India
2 Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, India
3 Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad; Department of Pathology, Sri Venkateshwara Institute of Medical Sciences Tirupati, Andhra Pradesh, India
4 Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad; Department of Pathology and Lab Medicine, Basavatharakam Indoamerican Cancer Hospital and Research Institute, Hyderabad, Telangana, India

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Date of Submission23-Apr-2020
Date of Decision30-May-2020
Date of Acceptance26-Jun-2020
Date of Web Publication9-Apr-2021


Background and Aims: Molecular analysis is gold standard for diagnosis of synovial sarcoma (SS) but use of these ancillary techniques is limited by many practical issues like cost and limited resources. Several studies analyzed TLE1 as a diagnostic immunohistochemical marker for synovial sarcoma and few studies disagreed. The objective of the study was to evaluate immunohistochemical expression of TLE1 in synovial sarcoma and its histological mimics. Methods: The study included a total of 63 cases; of which 28 were synovial sarcomas (SS) and 35 its histologic mimics. A tissue microarray was constructed from these cases and subjected to TLE immunostaining. Nuclear immunoreactivity of TLE1 was graded as 0, 1+, 2+ and 3+ based on intensity and percentage of cells.
Results: All SS except one (27/28; 96.4%) were positive for TLE 1. These included 18 of monophasic spindle cell type (94.7%), 5 biphasic type (100%), followed by two each (100%) of poorly differentiated and calcifying type of SS. Of the other tumours 2 GISTs (50%), 2 haemangiopericytoma (66.7%), 2 schwannomas (50%) and one mesenchymal chondrosarcoma (33.3%) were positive for TLE1. Conclusion: TLE 1 is a highly sensitive marker with reasonable specificity for synovial sarcoma. Awareness of TLE1 expression in other tumours, is important to avoid misdiagnosis.

Keywords: Histological mimics of synovial sarcoma, synovial sarcoma, TLE1

How to cite this article:
Sivakoti S, Uppin SG, Uppin MS, Tara RP, Prayaga Ak, Challa S. Tissue microarray based immunohistochemical study of TLE1 in synovial sarcoma and its histologic mimics. Indian J Pathol Microbiol 2021;64:310-5

How to cite this URL:
Sivakoti S, Uppin SG, Uppin MS, Tara RP, Prayaga Ak, Challa S. Tissue microarray based immunohistochemical study of TLE1 in synovial sarcoma and its histologic mimics. Indian J Pathol Microbiol [serial online] 2021 [cited 2021 May 8];64:310-5. Available from: https://www.ijpmonline.org/text.asp?2021/64/2/310/313295

Synovial sarcoma (SS) is a mesenchymal tumour, which displays a variable degree of epithelial differentiation, including gland formation, and has a specific chromosomal translocation t(X;18) (p11;q11) that leads to formation of a SS18-SSX fusion gene.[1],[2],[3],[4] It is the fourth most common high grade soft tissue sarcoma and accounts for 5-10% of all soft tissue sarcomas. Local control requires wide local excision, radiation therapy and chemotherapy to reduce microscopic metastasis. Beneficence of adjuvant therapy is unclear and causing significant morbidity in relatively young patients. Histologically, SS is subtyped into biphasic SS, monophasic SS, poorly differentiated SS and calcifying type.[5] The diagnosis of biphasic SS is generally straightforward, but the diagnosis of monophasic SS and poorly differentiated SS is challenging.

The current gold standard test for diagnosis of SS is demonstration of the characteristic translocation between the SS18 (SYT) gene on chromosome 18 and one of three SSX genes (SSX1, SSX2, or rarely SSX4) on chromosome X [t(X;18)(p11.2;q11.2)].[6],[7] Detection of t(X;18) can be accomplished by advanced molecular medical techniques like Karyotyping, fluorescence in situ hybridization (FISH) or reverse-transcriptase polymerase chain reaction (RT-PCR). The use of these advanced molecular techniques is not feasible practically due to lack of availability at many centers and cost factor. Thus, in practice, the diagnosis of SS in resource poor states is usually based on basic histopathological tests like histological examination in correlation with immunohistochemistry (IHC). Cytokeratin (CK), EMA and Bcl-2 are used to identify SS but have limited specificity and sensitivity. Transducin-like enhancer of split 1 (TLE 1) gene is a member of the TLE gene family and involved in control of hematopoiesis, neuronal, and terminal epithelial differentiation.[8],[9],[10] TLE 1 competes with β-catenin, which plays an important role in Wnt/β-catenin signaling pathway.[11],[12] Several studies analyzed TLE1 as a characteristic immunohistochemical marker for SS.[13],[14],[15],[16],[17] The study done by Kosemehmetoglu et al. concludes that TLE1 IHC may play a limited role in diagnosis of SS with sensitivity of 85% and specificity of 75%.[18] In the present study, we evaluated sensitivity and specificity immunohistochemical expression of TLE1 in SS and its histological mimics and its value as a diagnostic marker.

   Methods Top

This is a retrospective study. Slides (H and E, special stains and IHC slides) and paraffin blocks were retrieved from surgical pathology archives of Department of Pathology. The study was approved by the Institutional Ethics Committee. The study included 28 SS cases, 28 cases of monophasic SS mimics (4-Leiomyosarcoma, 4-Gastrointestinal stromal tumour, 3-Hemangiopericytoma, 3-Dermatofibro sarcoma protuberance, 3-Fibrosarcoma, 4-MPNST, 3-Solitary fibrous tumour and 4-schwannoma) and 7 cases of poorly differentiated sarcoma mimics (4-Ewing sarcoma and 3-mesenchymal sarcoma). The inclusion criteria for SS and its mimics included in the study are provided in [Table 1]. The original H and E and IHC slides of the tumour were reviewed to reconfirm the diagnosis and selective neoplastic areas devoid of hemorrhage and necrosis were recognized and marked on the corresponding tissue blocks. The tissue cores were extracted from the marked area and transferred into corresponding plots of tissue block for construction of Tissue microarray (TMA) using Quick-Ray needle of 5mm tip. Two cores were taken per case subject to availability of material.
Table 1: Inclusion criteria of synovial sarcoma and its histological mimic

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IHC analysis was carried out on 4μm thickness sections of TMA blocks using TLE1 (1F5) Mouse Monoclonal Antibody (CELL MARQUE, USA, 1 in 30 dilutions). This was performed on a semi-automated immunostainer (i6000, Biogenex) using Poly HRP technique.

Three cases showing SS18 break-apart by fluorescent in situ hybridization and showing positive staining with TLE 1 served as positive control. Nuclear immunoreactivity was graded as 0, 1+, 2+ and 3+ based on intensity and percentage of cells. More than 50% of the cells exhibiting intense positivity which is visible with a 4X objective, was graded as 3+; 25-50% of the cells exhibiting intense positivity or more than 50% of the cells showing moderate intensity which is visible on 10X objective was graded as 2+; 5-25% of the cells with intense positivity graded as 1+; less than 5% staining of tumour nuclei is graded as nil (0). Overall, sensitivity, specificity, positive predictive value, and negative predictive value of TLE 1were calculated.

   Results Top

The study included a total of 63 cases, of which 28 were SS and 35 other benign and malignant mesenchymal tumors which can histologically mimic SS. Of the included cases of SS, majority were monophasic spindle cell type (67.8%), followed by biphasic (17.8%), poorly differentiated (7.1%) and calcifying type (7.1%). IHC results of TLE1 immunostaining on TMA slides are summarized in [Table 2]. Of the total 126 cores of 63 cases, 4 cores were lost during the procedure. Due to this, one case could not be analyzed. The remaining two cores which were lost belonged to one core each from two different cases. In these cases, the left out cores of the same were analyzed. Disparity in grading between the two cores of the same case was observed in 3. In these cases, a higher grade was taken into consideration.
Table 2: Expression of TLE1 in tumors

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Grade 3+ and 2+ staining was taken as positive. Accordingly, TLE 1 positivity was observed in 27/28 (96.4%) cases of SS [Figure 1]. The other tumours which showed positivity include 2/4 (50%) GIST cases, 2/3 (66.6%) hemangiopericytoma, 2/4 (50%) schwannomas and 1/3 (33.3%) mesenchymal chondrosarcoma. All cases of leiomyosarcoma, Ewing sarcoma, dermatofibrosarcoma protuberance, fibrosarcoma, MPNST and solitary fibrous tumour included in the study were negative for TLE 1. Accordingly, TLE-1 showed a sensitivity of 96.4%, specificity of 80% with positive predictive value of 79.45% and negative predictive value of 96.5%. SS subtypes did not show much difference in TLE 1 immunostaining [Table 3]. In case of biphasic tumor, TLE-1 positivity was noted in both epithelial and mesenchymal component [Figure 1]d. Background staining is not observed in any of the tumour.
Figure 1: Shows Grade 3+, 2+ and 1+ nuclear expression of TLE1 in monophasic synovial sarcoma (a-c respectively); HE section of monophasic synovial sarcoma (a, insert). TLE 1 expression in biphasic synovial sarcoma showing Grade 3+ positivity in both spindle and epithelial component (d); HE section of biphasic synovial sarcoma (b, insert). (HRP-Polymer; ×400)

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Table 3: TLE1 staining in synovial sarcoma subtypes

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The isolated case of TLE1 negative SS was located around knee joint. Morphologically, it displayed monophasic spindle cell pattern. On the IHC tumor cells showed diffuse strong positivity for bcl2, patchy positivity for EMA, diffuse weak to moderate staining for CD99 while being negative for Pancytokeratin, SMA, CD34 and S-100 [Figure 2]. Molecular confirmation was not available for this case.
Figure 2: Monophasic synovial sarcoma showing (a) monomorphic spindle cells in short interlacing fascicles (H and E; ×200). Immunohistochemistry findings of the case showing (b) negative staining for TLE1, (c) diffuse strong positivity for bcl2, (d) patchy positivity for EMA, (e) diffuse weak to moderate positivity for CD99 and negative staining for (f) Pancytokeratin (g) CD34, (h) SMA and (i) S100 (B-I, HRP-Polymer; ×200)

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   Discussion Top

Synovial sarcoma has wide anatomic distribution and variable histologic patterns, which create diagnostic difficulties.[5] Monophasic fibrous SS can be difficult to distinguish from its histological mimics which include other spindle cell sarcomas such as malignant peripheral nerve sheath tumours, cellular schwannomas, solitary fibrous tumour, fibrosarcoma, DFSP, haemangiopericytoma, GIST and leiomyosarcoma. Though IHC is helpful in differentiation, in many cases there may be overlapping immunohistochemical results. Molecular analysis is the characteristic benchmark tests for diagnosis of SS but use of these ancillary techniques is limited by many practical issues like cost and limited resources. Many attempts have been made to identify highly specific, sensitive marker for SS.[19],[20] Gene expression studies showed overexpression of TLE family genes, particularly TLE 1 in SS.[21],[22]

Comparisons between our study results and those of previous studies are summarized in [Table 4]. In the present study, sensitivity and specificity of TLE 1 for SS is 96.4% and 80%, respectively, which is similar to several other reported studies. The reported sensitivity in previous studies has ranged from 82-100% and specificity from 72-96%. Grading system used in the present study for TLE1 positivity was similar to that followed by Terry et al., Jagdis et al., Rekhi et al. and Xin he et al.[13],[14],[17],[23] Our sensitivity was similar to these four studies. The other two studies by Kosemehmetoglu et al. and Foo et al. showed lesser sensitivity.[18],[15] However, these studies employed different grading scheme to asses TLE1 positivity. The percentage of cases with grade 3+ (74%) positivity was higher than grade 2+ positive cases in the present study which is similar to that reported by Terry et al. and Rekhi et al.[13],[17] The only negative case of SS in the present series was a case of MSS which showed grade 0 staining. Though this case had classical morphology and IHC findings of SS, molecular confirmation was not done. One of the limitations of the present study compared to others was inclusion criteria for SS, which was mainly based on morphology and IHC findings while others included molecularly confirmed cases. We tried to overcome this by using rigid morphological and IHC criteria for inclusion as SS. The correlation of our study results with that of other studies further strengthens our inclusion criteria. Though in the present and that of Terry et al.,[13] IHC was carried out on tissue microarray, the results were comparable to other studies which used whole sections.[14],[15],[17],[18] There was no significant difference in sensitivity for TLE1 among various histological types of SS included in the present study. Foo et al. observed higher sensitivity for PDSS (91%) when compared to overall sensitivity for SS (82%).[15]
Table 4: Comparison between present study and previous studies

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There was variation in the entities as well as number of cases of mimics included in different studies to analyze specificity of TLE 1. The positivity of MPNST to TLE 1 reported in previous studies ranges from 2.3-30%. In the present study all were negative, with 2 of them showing grade 1 staining. Schwannomas have also shown wide range of positivity ranging from 0-100%. In our study, 2/4 cases (50%) of schwannomas showed positive staining. Analysis of TLE 1 on GIST was done in few previous studies. Kosemehmetoglu et al. and Rekhi et al. reported negative results in 6 and 1 cases studied by them, respectively.[17],[18] Terry et al. studied 35 cases of GIST and showed positivity in 6% of their cases.[13] We studied 4 cases of GIST, of which 2 (50%) were positive for TLE1. Both these were CD117 and DOG1 positive cases. TLE1 was negative in all the 4 molecularly proven cases of Ewings sarcoma included in the present study. Similar results were reported by many other studies as well except for the study by Rekhi et al., who demonstrated positivity in 40% of their cases.[17] This could be due to different sensitivity of the antibody clone used. Xin he et al. analyzed TLE1 immunostaining in mesenchymal chondrosarcoma and found to be negative in all 11 cases.[23] But we found positivity in 33.4% (1/3) cases. Haemangiopericytoma was positive in 2/3 cases (66.6%) in present study. Terry et al. observed positivity in 40% cases and Xin he et al. did not find any positivity.[13],[23] TLE 1 expression in leiomyosarcoma has been low ranging from 2-20% in the previous studies.[13],[17],[18] In the present series, all the cases of leiomyosarcomas were negative. This may be due to use of monoclonal antibody in present study where all other previous studies used polyclonal antibody. Similar to other studies, dermatofibrosarcoma protuberance and fibrosarcoma included in the present study were negative for TLE1.

We observed that most of the tumours other than SS showed less intensity of positivity to TLE1. Chaung et al. also observed the same and concluded that grading could differentiate SS from other tumours.[24] Jagdis et al. reported a negative predictive value of TLE1 to be 100%, which was slightly higher than 96.5% noted in present series. But positive predictive value of 79.4% in our study was less when compared to that reported by Jagdis et al. (92%) study.[14] This could be due to the different types and number of SS mimics studied. We studied GIST and mesenchymal chondrosarcomas, some of which showed positive staining with TEL1 but these cases were not included by Jagdis et al.

To conclude, TLE 1 is a sensitive marker for SS with high negative predictive value and reasonably good positive predictive value. Specificity of TLE 1 for the diagnosis SS can be increased by using in combination with other IHC markers like Bcl2, Pan cytokeratin, EMA, calponin and CD34. Although molecular confirmation remains the gold standard, immunohistochemical studies for TLE1 are valuable in differential diagnosis, especially when access to molecular testing is limited. Correlating clinical, histomorphology and TLE1 expression pattern in SS reduce the diagnostic difficulty and helps in accurate diagnosis without the aid of molecular tests. The knowledge of TLE1 expression in other spindle cell tumours should be considered during interpretation, which helps us in making corrective diagnosis and increase in specificity.

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Conflicts of interest

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Correspondence Address:
Shantveer G Uppin
Professor, Department of Pathology, Nizam's Institute of Medical Sciences, Hyderabad, Telangana,500 082
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/IJPM.IJPM_425_20

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  [Table 1], [Table 2], [Table 3], [Table 4]


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