Is immunohistochemical staining for β-catenin the definitive pathological diagnostic tool for desmoid-type fibromatosis? A multi-institutional study

Extensive Lateral Cervical Desmoid Tumor Dependent on the Levator Scapulae Muscle Involving the Vertebral Artery Treated by Surgical Resection and Intraoperative Navigation: A Case Report and Review of the Literature

Desmoid tumors are rare, benign, but locally aggressive fibromatoses that pose significant therapeutic challenges, particularly when located in the head and neck region. This report details the case of an extensive cervical desmoid tumor dependent on the levator scapulae muscle and involving the vertebral artery managed through surgical resection and intraoperative navigation. A 45-year-old male presented with a slowly growing cervical mass. Imaging revealed an 83x68x40 mm mass in the right lateral paravertebral space, dependent on the levator scapulae muscle and involving the vertebral artery. Biopsy confirmed a low-grade fusocellular myofibroblastic neoplasm consistent with a desmoid tumor. Given the poor prognosis associated with the symptomatic mass, surgical resection was performed using Brainlab intraoperative navigation (Brainlab, Munich, Germany). The procedure was successful, with preservation of vital structures and no evidence of recurrence postoperatively. Desmoid tumors in the head and neck region, though rare, require precise diagnostic and therapeutic approaches due to their aggressive nature and proximity to critical anatomical structures. The use of intraoperative navigation, in this case, facilitated accurate tumor resection, minimizing damage to surrounding tissues. Pathological analysis revealed a CTNNB1 gene mutation, specifically the S45P variant, which is associated with an increased risk of recurrence. This case highlights the importance of a multidisciplinary approach, incorporating advanced surgical techniques and genetic analysis, in the management of complex desmoid tumors. Intraoperative navigation proved invaluable in achieving successful surgical outcomes, underscoring its potential utility in similar cases. Continued follow-up is essential, given the potential for recurrence associated with desmoid tumors.

RAD51C and MYST3 Mutations in a Case of Desmoid-Type Fibromatosis With No Mutation in CTNNB1 or APC

Most cases of desmoid-type fibromatosis (DTF) exhibit a mutation in APC or CTNNB1. We report a case of mesenteric DTF in which no mutation in APC or CTNNB1 was found, but a germline variant of uncertain significance (VUS) in RAD51C and a subclonal mutation in MYST3 were identified. Whether these genetic changes are important in DTF in this case, or whether genetically conventional DTF cells were present at a density below detection is unknown; it will be of interest to see results in further studies of wild-type APC/CTNNB1 cases.

Fetal Type Morphologies Suggest the Presence of DICER1 Hotspot Mutations in Non-small Cell Lung Cancer

Germline and somatic pathogenic variants (PVs) in DICER1 , encoding a miRNA biogenesis protein, are associated with a wide variety of highly specific pathologic entities. The lung tumors pleuropulmonary blastoma, pulmonary blastoma (PB), and well-differentiated fetal lung adenocarcinoma (WDFLAC) are all known to harbor DICER1 biallelic variants (loss of function and/or somatic hotspot missense mutations), and all share pathologic features reminiscent of the immature lung. However, the role of DICER1 PVs in non-small cell lung cancer (NSCLC) is relatively unknown. Here, we aimed to establish the spectrum of lung pathologies associated with DICER1 hotspot PVs and to compare the mutational landscape of DICER1 -mutated NSCLC with and without hotspots. We queried DNA sequencing data from 12,146 NSCLCs featuring somatic DICER1 variants. 235 (1.9%) cases harboring ≥ 1 DICER1 PV were found and 9/235 (3.8%) were DICER1 hotspot-positive cases. Histologic review of DICER1 hotspot-positive cases showed that all but one tumor were classified as within the histologic spectrum of PB/WDFLAC, whereas all the DICER1 non-hotspot double variants were classified as lung adenocarcinomas, not otherwise specified. Comparison between the mutational landscape of DICER1 hotspot-positive and hotspot-negative cases revealed a higher frequency of CTNNB1 mutations in the hotspot-positive cases (5/9 vs. 2/225; P <0.00001). We conclude that DICER1 somatic hotspots are not implicated in the most common forms of NSCLC but rather select for morphologic features of lung tumor types such as PB and WDFLAC. As a corollary, cases showing this tumor morphology should undergo testing for DICER1 variants, and if positive, genetic counseling should be considered.

Mesenchymal tumours of the pleura: review and update

Primary mesenchymal tumours of the pleura are uncommon and can be diagnostically challenging due to their overlapping histopathologic and immunophenotypic features. Herein we discuss selected mesenchymal tumours of the pleura, including solitary fibrous tumour, calcifying fibrous tumour, desmoid fibromatosis, synovial sarcoma, schwannoma, malignant peripheral nerve sheath tumour, inflammatory myofibroblastic tumour, follicular dendritic cell sarcoma, epithelioid hemangioendothelioma, and desmoplastic small round cell tumour. We review their clinicopathologic characteristics, along with an update on the relevant immunohistochemical and molecular features.

Skin Malignancies: Imaging Review with Radiologic-Histopathologic Correlation

Skin malignancies are commonly encountered as primary or incidental findings. Neoplasms that affect the skin include primary (basal cell carcinoma, squamous cell carcinoma, melanoma, and Merkel cell carcinoma) and secondary (mesenchymal neoplasms, lymphoma, and metastases) tumors. Imaging provides valuable anatomic information (tumor size, depth of involvement, presence of distant metastasis, and data for guiding biopsy) and functional information (metabolic activity and sentinel node mapping data). This information, in addition to biopsy results, improves the histopathologic characterization of tumors and treatment planning. Various histopathologic types of the same entity exhibit different biologic behavior and have different imaging features. Familiarity with the multimodality imaging features, histopathologic characteristics, and various modes of dissemination (direct invasion; perineural, lymphatic, and hematogenous spread) of the most common skin malignancies helps radiologists narrow the differential diagnosis in clinical practice. ©RSNA, 2023 Supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Infantile Sinonasal Myxoma Is Clinically and Genetically Distinct From Other Myxomas of the Craniofacial Bones and From Desmoid Fibromatosis

Sinonasal myxomas are rare benign tumors of the maxillary bone and sinus. There is published evidence that sinonasal myxomas occurring in children up to 3 years of age ("infantile sinonasal myxomas") are clinically distinctive and harbor Wnt signaling pathway alterations. Here, we characterized 16 infantile sinonasal myxomas and compared them to 19 maxillary myxomas and 11 mandibular myxomas in older patients. Clinical follow-up was available for 21 patients (46%) overall (median: 2.6 y; range: 4 mo to 21 y), including 10 of 16 infantile sinonasal myxomas (62%). None of the 8 resected infantile sinonasal myxomas recurred, despite positive margins in 6 of them. One incompletely resected infantile sinonasal myxoma underwent partial regression without additional treatment. In contrast, 4 of the 11 other myxomas with follow-up recurred (36%), including one that recurred twice. Imaging studies demonstrated all infantile sinonasal myxomas to be expansile lesions arising from the anterior maxillary bone adjacent to the nasal aperture, with peripheral reactive bone formation. Histologically, infantile sinonasal myxomas showed short, intersecting fascicles of bland fibroblastic cells with prominent stromal vessels. Examples with collagenous stroma showed some morphologic overlap with desmoid fibromatosis, although none showed infiltrative growth into adjacent soft tissue. Immunohistochemistry demonstrated nuclear β-catenin expression in 14 of 15 infantile sinonasal myxomas (93%), in contrast to 4 of 26 other myxomas of craniofacial bones (15%). Smooth muscle actin was expressed in only 1 of 11 infantile sinonasal myxomas (9%). Next-generation sequencing was successfully performed on 10 infantile sinonasal myxomas and 7 other myxomas. Infantile sinonasal myxomas harbored CTNNB1 point mutations in 4 cases (D32Y, G34E, G34R, and I35S), and none harbored alterations to the phosphorylation sites T41 and S45 that are altered in 99% of CTNNB1 -mutant desmoid fibromatoses. Three tumors showed alterations consistent with biallelic APC inactivation. Three infantile sinonasal myxomas that showed strong nuclear β-catenin expression were negative for CTNNB1 and APC alterations. Sequencing was negative for CTNNB1 or APC alterations in all 7 myxomas of craniofacial bones in older patients. Four of these myxomas in older patients (57%) showed copy number alterations, and all lacked known driving alterations. These findings support the notion that infantile sinonasal myxomas are clinically and genetically distinctive, and we propose the use of the diagnostic term "infantile sinonasal myxoma" to distinguish this tumor type from other myxomas of the craniofacial bones. Infantile sinonasal myxoma should be distinguished from desmoid fibromatosis because of its unique clinical presentation, more indolent clinical behavior, different morphology, different immunohistochemical profile, and different genetics. Given its indolent behavior even when marginally excised, infantile sinonasal myxoma can be managed with conservative surgery.

Tuberous sclerosis complex mutations in patients with pancreatic neuroendocrine tumors. Observations on phenotypic and treatment-related associations

Pancreatic neuroendocrine tumors (PanNETs) in familial tuberous sclerosis (TSC1 and TSC2 mutations) have been known and studied. However, little is known about PanNET patients harboring the very rare (less than 2%) sporadic TSC mutations. Some renal tumors have been shown to harbor sporadic TSC mutations, with a distinctive morphological correlate. We hereby describe this rather unusual molecular alteration in well-differentiated pancreatic neuroendocrine tumors (WD PanNETs) with a focus on their morphology and treatment outcomes. Six cases of WD PanNETs harboring sporadic TSC mutations were identified retrospectively. H&E slides and corresponding immunostains were reviewed for all cases. Clinical, molecular, and radiological information was obtained using the electronic medical records. Cohort consisted of 4 males and 2 females. Median age at diagnosis was 50 years (range 33-74 years). Origin of neoplasm was the pancreas and, in all but one, patient had liver metastasis by the time of presentation. Six out of six cases demonstrated a unique tumor morphology, with ample eosinophilic cytoplasm. Tumors were arranged in sheets and nests; prominent cystic change was noted in one case. Two cases were additionally biopsied post-treatment with capecitabine and temozolomide, and showed even more abundant oncocytic cytoplasm, eccentric nuclei, and a prominent cherry red nucleolus, and were arranged in a cluster of 3-4 cells, separated by stromal cells. Every patient had a different TSC2 variant with no cases of TSC1 mutations. Other common variants included MEN1 (4/6), DAXX (2/6), and TP53 (2/6). Per the WH0 2019 classification, tumors were graded as NET-G3 (n = 3) and NET-G2 (n = 3). Ki-67 s ranged from 7.2 to 60. All cases had retained MMR protein expression. The majority of patients (4/6) have expired. Although they received multiple treatments, a consistent pattern observed in patients was marked radiologic response to chemotherapy with capecitabine and temozolomide (offered in 5/6 patients) with duration of responses reaching 11 months in the majority of cases, with one patient showing near complete pathologic response of localized disease. TSC2 mutations may confer distinctive appearance in WD PanNETs, reminiscent of their effects in renal tumors. Although not entirely specific, this distinct morphological pattern with abundant eosinophilic cytoplasm in WD PanNETs could be reflective of an associated TSC mutation, with suggestions of significant therapeutic response to a specific cytotoxic chemotherapy.

Adenoid Ameloblastoma Shares Clinical, Histologic, and Molecular Features With Dentinogenic Ghost Cell Tumor: The Histologic Spectrum of WNT Pathway-Altered Benign Odontogenic Tumors

An epithelial odontogenic tumor called adenoid ameloblastoma (AA) has recently been included in the new WHO classification. However, AA has considerable overlapping features with a preexisting entity, dentinogenic ghost cell tumor (DGCT). This study compared the clinical, histologic, and molecular characteristics of AA and DGCT. Eight cases of odontogenic tumors initially diagnosed as AA or DGCT were included in this study. Quantitative histologic analysis, β-catenin immunohistochemistry, and molecular profiling using next generation sequencing were performed. Additionally, accumulated clinical data of AA and DGCT were statistically analyzed. Nuclear β-catenin accumulation was detected in all cases in common, although the tumors studied histologically consisted of varying combinations of the AA-like phenotype, ghost cells, and dentinoid. However, CTNNB1 hotspot mutations were not found in any case. Instead, loss-of-function mutations in tumor suppressor genes involved in the WNT pathway, including the APC, SMURF1, and NEDD4L genes, were found regardless of histologic type. In addition, KRT13 mutations were detected in 2 cases with a high proportion of ghost cells. Finally, a literature analysis revealed clinical similarities between the previously reported cases of AA and DGCT. These findings suggest that from a clinical and molecular point of view, AA and DGCT represent a histologic spectrum of WNT pathway-altered benign odontogenic tumors rather than 2 distinct tumors. Moreover, previously unidentified keratin mutations may be associated with ghost cell formation found in specific types of odontogenic lesions.

Molecular testing of soft tissue tumors

BACKGROUND

The diagnosis of soft tissue tumors is challenging, especially when the evaluable material procured is limited. As a result, diagnostic ancillary testing is frequently needed. Moreover, there is a trend in soft tissue pathology toward increasing use of molecular results for tumor classification and prognostication. Hence, diagnosing newer tumor entities such as CIC-rearranged sarcoma explicitly requires molecular testing. Molecular testing can be accomplished by in situ hybridization, polymerase chain reaction, as well as next generation sequencing, and more recently such testing can even be accomplished leveraging an immunohistochemical proxy.

CONCLUSION

This review evaluates the role of different molecular tests in characterizing soft tissue tumors belonging to various cytomorphologic categories that have been sampled by small biopsy and cytologic techniques.

Immunohistochemical staining of LEF-1 is a useful marker for distinguishing WNT-activated medulloblastomas

Objectives

To investigate lymphoid enhancer factor 1 (LEF-1) protein expression in medulloblastomas (MBs) and its correlation with molecular grouping of MBs.

Methods

Expressions of LEF-1 and β-catenin were detected by immunohistochemistry, and molecular grouping was performed based on the NanoString and sequencing techniques for 30 MBs.

Results

By genetic defining, 3 MBs were WNT-activated, 11 were SHH-activated, 3 were in Group 3 and 13 in Group 4 respectively. Nuclear LEF-1 staining was found in 8 MBs using immunohistochemical method. Three out of 8 showed diffuse and strong nuclear LEF-1 staining which were proved to be WNT-activated genetically, while the other 5 MBs with focal staining were SHH-activated genetically. The expression of LEF-1 protein was significantly correlated with genetically defined WNT-activated MBs (P < 0.0001). We also found focal nuclear β-catenin expression ( less than 1% of tumor cells) in 5 MBs. LEF-1 positivity was significantly correlated nuclear β-catenin expression (p < 0.001).

Conclusions

Immunohistochemical staining of LEF-1 can be used as a supplement for β-catenin to diagnosis WNT-activated Medulloblastomas, when β-catenin is difficult to recognize for its cytoplasm/membrane staining background. Diffuse nuclear staining of LEF-1 indicates WNT-activated MB.

Biclonal Desmoid-Type Fibromatosis With Two Beta-Catenin Mutations: Evidence for the Recruitment of Normal Myofibroblasts

Sporadic aggressive fibromatosis, or desmoid-type fibromatosis, is characterized by oncogenic mutations in CTNNB1. The clonal cell is a myofibroblast-like cell, and it has been hypothesized that the recruitment of normal myofibroblasts could contribute significantly to the tumor. We describe a case in which a CTNNB1 p.T41A mutation was present at a mutant allele frequency of 30%, suggesting that a significant proportion of the tumor myofibroblasts may have been recruited from normal precursor pools. In addition, a small subclone with a p.S45F mutation (allele frequency of 2%) was identified in the tumor. This case provides additional evidence that myofibroblasts recruited by a tumor from a normal precursor pool contribute significantly to the tumor; such recruitment could impact response to treatment and long-term outcomes.

Trends in diagnostic and therapeutic strategies for extra-abdominal desmoid-type fibromatosis: Japanese musculoskeletal oncology group questionnaire survey

OBJECTIVE

The mainstay of treatment modality for extra-abdominal desmoid-type fibromatosis (DF) has shifted from surgery, which often impairs ADL/QOL, to conservative treatment including active surveillance. In the present study, we conducted a longitudinal survey on the diagnosis and treatment of DF at facilities belonging to the Japanese Musculoskeletal Oncology Group, which is a research group of facilities specializing in the treatment of bone and soft tissue tumors in Japan to clarify the transition of medical care for extra-abdominal DF.

METHODS

The same questionnaire was administered in 2015 and 2018, and responses were obtained from 46 (69%) of 67 facilities and 42 (53%) of 80 facilities in 2015 and 2018, respectively.

RESULTS

Although immunostaining for β-catenin was often used for the pathological diagnosis in both 2015 and 2018, CTNNB1 mutation analysis was not performed either in 2015 or in 2018. As for the treatment strategy for resectable cases, surgical treatment including wide resection was selected at 11 facilities (24% of respondents) in 2015, and further decreased to 5 facilities (12%) in 2018. Conservative treatment with active surveillance or medical treatment was the most common treatment for both resectable and difficult-to-resect cases. COX-2 inhibitors and tranilast were often used in the drug treatment of both resectable and difficult-to-resect cases. Few facilities provided radiotherapy, methotrexate and vinblastine, or DOX-based chemotherapy for refractory cases in both 2015 and 2018.

CONCLUSIONS

A good trend was found in the questionnaire survey. It will be further necessary to disseminate clinical practice guidelines to physicians more widely, and to have them understand and implement the most up-to-date medical practice strategies for this rare disease.

PIK3CA mutation in a case of CTNNB1 mutant sinonasal glomangiopericytoma

Glomangiopericytomas are rare, primary sinonasal tumors. The existing literature is mostly limited to reports describing the clinicopathologic characteristics of these tumors. Comprehensive genetic characterization of glomangiopericytomas remain lacking. Whole exome sequencing of a case of glomangiopericytoma was performed under an institutional review board approved protocol. A 69 year-old female underwent surgical resection of a glomangiopericytoma. Whole exome sequencing revealed somatic mutations in CTNNB1 and PIK3CA, the former previously associated with this pathology but the latter not described. Concurrent dysregulation of Wnt/beta-catenin and PI3K/AKT/mTOR signaling, secondary to mutations in these two oncogenes may be amenable to targeted treatment with existing clinically approved drugs. Genomic characterization of glomangiopericytomas remains lacking. This study reports novel co-existence of PIK3CA and CTNNB1 mutations in a case of glomangiopericytoma that may offer insight into the pathogenesis and potential for targeted medical therapies of this rare tumor.

Epstein-Barr Virus-Associated Smooth Muscle Tumors of Larynx: A Clinicopathologic Study and Comprehensive Literature Review of 12 Cases

Laryngeal mesenchymal neoplasms are rare, with smooth muscle tumors comprising a small subset. Specifically, Epstein-Barr virus (EBV)-associated smooth muscle tumors are exceptionally rare, lacking a comprehensive evaluation of their clinical and histologic features. Two patients (a 59 year old male and 51 year old female) had received renal transplants 156 and 240 months, respectively prior to onset of laryngeal symptoms. Supraglottic polypoid masses were identified and removed conservatively. Histologically, the tumors were hypercellular, showing alternating light and dark areas, the latter composed of primitive appearing round cells, while a more characteristic spindled tumor cell population was noted in the remaining areas. Cytoplasmic vacuoles were noted adjacent to the nucleus. There was no tumor necrosis or pleomorphism, but increased mitotic figures (11-12/2 mm²) were seen, without atypical forms. The tumor cells were strongly immunoreactive with smooth muscle actin and smooth muscle myosin heavy chain and with Epstein-Barr virus encoded RNA (EBER) by in situ hybridization. These patients were reviewed in the context of a thorough English literature review, which demonstrates a wide age range at presentation without a sex predilection, but with most patients from specific ethnic groups (Chinese, Thai, Pilipino). Three-quarters of patients are part of multifocal disease and the majority are post-renal transplantation patients. Conservative management seems to yield the best overall outcome for these indolent tumors. In conclusion, EBV-associated smooth muscle tumors should be considered in any immunocompromised patient with a head and neck smooth muscle tumor, especially when EBER is documented by in situ hybridization. Conservative management may be employed, even when multifocal tumors are documented.

A comparison of the usefulness of nuclear beta-catenin in the diagnosis of desmoid-type fibromatosis among commonly used anti-beta-catenin antibodies

Desmoid-type fibromatosis (DF) is a locally aggressive but non-metastatic (myo)fibroblastic neoplasm. A hallmark of the tumor is nuclear positivity for beta-catenin in immunohistochemistry due mostly to CTNNB1 mutations. However, a recent study has reported that even beta-catenin 'nuclear-negative' DFs can harbor CTNNB1 mutations and that the positive ratio of nuclear beta-catenin in DF is different among antibodies. Here, we reviewed soft tissue lesions for which the possibility of DF was considered and compared the sensitivity and specificity of nuclear beta-catenin for the diagnosis of DF among commonly used anti-beta-catenin antibodies, i.e., clone beta-catenin 1, 17C2 and 14. We analyzed 26 cases of DF, 28 cases of benign fibroblastic lesions, and 27 cases of other soft tissue tumors. The sensitivity and specificity of nuclear beta-catenin for the diagnosis of DF were different among antibodies; 54% and 98% in clone beta-catenin 1, 85% and 84% in 17C2, and 96% and 62% in 14. IHC of LEF1 showed comparable results with IHC of beta-catenin, with a sensitivity of 88% and specificity of 76%. Additionally, when beta-catenin 1 was used, DFs showed characteristic dotted cytoplasmic staining, often appearing as rings. Our results might be helpful for making a correct diagnosis of DF.

Is mutation analysis of β-catenin useful for the diagnosis of desmoid-type fibromatosis? A systematic review

BACKGROUND

An accurate diagnosis is crucial to determine the treatment modality for desmoid-type fibromatosis, although the histopathological diagnosis is occasionally difficult to make. Many desmoid-type fibromatosis have been reported to have hotspot mutation of β-catenin gene (CTNNB1). In the present study, we performed a systematic review to verify the usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis.

METHODS

A literature search from January 1990 to August 2017 was conducted. Three reviewers independently assessed and screened the literature for eligibility and determined the final articles to be evaluated. Data regarding the sensitivity, specificity, accuracy and usefulness of CTNNB1 mutation analysis in the diagnosis of desmoid-type fibromatosis were recorded. We rated each report according to the Grading of Recommendations Development and Evaluation approach.

RESULTS

The search yielded 90 studies, seven of which were included after the first and second screenings. The positive rate of CTNNB1 mutation in desmoid-type fibromatosis was 86.8%, but the cohort of six of the seven reports was already diagnosed histopathologically as desmoid-type fibromatosis. Therefore, the usefulness of CTNNB1 mutation analysis in a cohort that is difficult to diagnose histopathologically is not clear in this review. Nevertheless, CTNNB1 mutation showed very high specificity in desmoid-type fibromatosis, indicating the usefulness of CTNNB1 mutation analysis in its diagnosis in combination with histological examination.

CONCLUSION

Because the lack of data precludes any useful comparison with histological diagnosis, the evidence level is low. However, considering its specificity, CTNNB1 mutation analysis may be useful in cases in which the histopathological diagnosis is difficult.

Next-Generation Sequencing in the Diagnosis of Rare Pediatric Sinonasal Tumors

The diagnosis of desmoid fibromatosis or other spindle cell tumors in the sinonasal region is very rare in children and needs to be thoroughly confirmed with immunohistochemical and/or molecular tests. We report 2 patients with such rare tumors and describe the use of next-generation sequencing in their evaluation. A 3-year-old female had a 4.4-cm midline nasal cavity mass involving the bony septum and extending into the base of the skull bilaterally. The moderate cellular fibroblastic proliferation revealed areas of thick keloid-like collagen bands and other areas with myxoid edematous stroma. Deep targeted sequencing identified a novel G34V mutation in the CTNNB1 gene consistent with desmoid fibromatosis. An 11-month-old male infant presented with a right nasal mass that extended through the cribriform plate into the anterior cranial fossa and involved the right ethmoid sinus and adjacent right orbit. Histology revealed an infiltrative atypical fibrous proliferation with focal calcifications that was negative for CTNNB1 and GNAS mutations. A novel RET E511K variant was identified in the tumor and later was also found in the germline and hence rendered of unknown significance. Both cases highlight the utility of next-generation sequencing in the evaluation of pediatric sinonasal spindle cell tumors that may have overlapping pathologic features. Reporting of rare or novel variants in tumor-only sequencing should be cautiously evaluated in children and pairing with germline sequencing may be needed to avoid the pitfall of assigning uncommon variants.

Nuclear TFE3 expression is a diagnostic marker for Desmoid-type fibromatosis

BACKGROUND

Desmoid-type fibromatosis (DTF) is a lesion characterized by clonal proliferation of myofibroblasts, which exhibits an infiltrative growth pattern. It is necessary for them to be distinguished from other fibroblastic and myofibroblastic lesions as well as spindle cell tumors. Altered Wnt signaling can act as a defining characteristic of DTF, with nuclear β-catenin serving as a diagnostic marker for. Transcription factor E3 (TFE3) has been linked to Wnt pathway activation and regulation, and may add value to the diagnosis of DTF. The present study, therefore, sought to assess whether TFE3 is a specific diagnostic marker for DTF.

METHODS

Nuclear TFE3 and β-catenin staining was performed on a wide range of tumor types such as DTF (n = 46), nodular fasciitis (n = 14), neurofibroma (n = 5), dermatofibrosarcoma protuberans (n = 5), gastrointestinal stromal tumor (n = 10), sclerosing epithelioid fibrosarcoma (n = 2), synovial sarcoma (n = 5), leiomyoma (n = 3) and cutaneous scar tissue (n = 4) using an immunohistochemical approach. In addition, the clinicopathological features and localization of these tumors were summarized. FISH assay was carried out to examine Xp11.2 translocations/TFE3 gene fusions. Statistical difference between immunohistochemical expression of TFE3 and β-catenin was analyzed.

RESULTS

The expression of nuclear TFE3 protein was found in 43 (93.5%) DTF tissue samples, ranging from moderate to intense expression levels. The distribution rates of TFE3 positivity in nodular fasciitis, gastrointestinal stromal tumor, leiomyoma and scar tissue samples were 42.9, 40, 25 and 33%, respectively. All studied samples of neurofibroma, synovial sarcoma, sclerosing epithelioid fibrosarcoma and dermatofibrosarcoma protuberans were negative for TFE3.

CONCLUSIONS

This study reveal that TFE3 has a potential to serve as a diagnostic marker capable of assisting in the differential diagnosis of DTF and other spindle cell lesions.