Histopathological, immunohistochemical and molecular spectrum of myoepithelial tumours of soft tissues

A Rare Case of a Malignant Epithelioid Neoplasm With an Underlying Novel EWSR1::ZBT44 Fusion, Identified on Next-Generation Sequencing (NGS)

The clinicopathological spectrum of undifferentiated round cell sarcomas of bone and soft tissues is expanding after the 5th edition of the WHO classification. A 23-year-old male patient presented with a lump in his left thigh of 3 months' duration. Radiological examination revealed a well-defined, solid-cystic lobulated, soft tissue lesion in the proximal medial region of his left thigh, measuring 7.7 cm in the largest dimension. The referring diagnosis was an epithelioid sarcoma. Histopathological review of the tumor sections revealed a cellular tumor composed of malignant epithelioid to focally "rhabdoid-like" cells in a variable hyalinized and myxoid stroma with geographic areas of necrosis. In addition, there were areas reminiscent of hemangiopericytomatous vasculature. By immunohistochemistry, the tumor cells were diffusely positive for CD34, focally and distinctly for pan keratin (AE1/AE3). INI1/SMARCB1 and SMARCA4 (BRG1) were diffusely positive (normal). Next-generation sequencing with a wide sarcoma panel revealed EWSR1exon8::ZBT44exon4 fusion. The present example constitutes the first malignant epithelioid tumor with a hemangiopericytomatous growth pattern, exhibiting this rare fusion. The differential diagnoses of this tumor and their corresponding immunohistochemical profile are discussed. This example highlights the value of NGS in unraveling rare fusions and in differentiating these tumors from their several mimics.

Impending Doom: A Rare Case of Metastatic Myoepithelial Carcinoma

Myoepithelial carcinoma is a rare malignant tumor arising from myoepithelial cells. The usual sites of occurrence are the oral cavity and pharynx with the majority of tumors arising from the salivary gland. However, there have been reported cases of myoepithelial carcinoma seen in the superficial soft tissue, upper respiratory tract, breast, skin, and GI tract. Deep soft tissue myoepithelial carcinoma is relatively uncommon. 

Due to the rarity of this malignancy, consensus on appropriate therapy remains sparse. However, complete resection and/or adjuvant chemotherapy and radiotherapy have been advocated for non-metastatic localized diseases. Sadly, the reported outcome in patients with metastatic disease remains dismal.

In this case, we report a 79-year-old male incidentally found to have a deep soft tissue mass in the sacral area with a coexistent left axillary lymphadenopathy with biopsy and immunohistochemistry confirmation of metastatic myoepithelial carcinoma. He had a rapid clinical deterioration with subsequent fatality.

Myoepithelial tumor in the popliteal area: A diagnostic dilemma

Introduction and importance

Myoepithelial tumors are under-recognized neoplasms that could be difficult to identify due to their rarity and limited comprehension. Their diverse morphology, varied cytologic features and heterogenous immunohistochemical characteristics create a significant diagnostic challenge.

Case presentation

We report the case of a 72-year-old-male patient who received conservative treatment during one year for a popliteal mass on the right knee that showed synovial hyperplasia (benign findings) at initial open tissue biopsy. New symptoms of popliteal area enlargement and discomfort required a second incisional biopsy to reach the diagnosis of a soft tissue myoepithelial tumor through tissue analysis and immunohistochemical staining.

Clinical discussion

The myoepithelial tumors represent a medical dilemma due to their heterogenic features requiring high level of suspicion and adequate immunohistochemical markers for their diagnosis.

Conclusion

Orthopaedic surgeons should be aware of the atypical presentation of these rare neoplasms to provide an early diagnosis and adequate management.

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Consider myoepithelial tumor within the differential of a soft tissue mass.

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Immunohistochemical markers are essential for diagnostic confirmation.

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Surgical resection with negative margins remains the mainstay of treatment.

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There is limited evidence regarding radiotherapy or chemotherapy effectiveness.

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This case highlights the deceiving nature and an unusual location of a myoepithelial tumor.

The Biology of Synovial Sarcoma: State-of-the-Art and Future Perspectives

New molecular insights are being achieved in synovial sarcoma (SS) that can provide new potential diagnostic and prognostic markers as well as therapeutic targets. In particular, the advancement of research on epigenomics and gene regulation is promising. The concrete hypothesis that the pathogenesis of SS might mainly depend on the disruption of the balance of the complex interaction between epigenomic regulatory complexes and the consequences on gene expression opens interesting new perspectives. The standard of care for primary SS is wide surgical resection combined with radiation in selected cases. The role of chemotherapy is still under refinement and can be considered in patients at high risk of metastasis or in those with advanced disease. Cytotoxic chemotherapy (anthracyclines, ifosfamide, trabectedin, and pazopanib) is the treatment of choice, despite several possible side effects. Many possible drug-able targets have been identified. However, the impact of these strategies in improving SS outcome is still limited, thus making current and future research strongly needed to improve the survival of patients with SS.

Expression patterns for Bcl-2, EMA, β-catenin, E-cadherin, PAX8, and MIB1 in thymomas

The expression of immunohistochemical markers has been extensively investigated in thymomas to assist in the differential diagnosis. We have studied six select markers to determine their utility in the evaluation of these tumors. A series of 126 thymomas including 33 type A, 27 type AB, 20 type B1, 22 type B2, and 24 type B3, were examined utilizing a tissue microarray (TMA) technique with antibodies to e-cadherin, β-catenin, PAX8, bcl-2, EMA, and MIB-1. Keratin AE1/AE3 and p63 were used for quality control. A significant finding was strong and consistent positivity for bcl-2 in type A (90%) and type AB (88.8%) thymoma, while 100% of B1, B2, and B3 were negative. The distribution of e-cadherin and β-catenin was not useful for differential diagnosis. E-cadherin and β-catenin were expressed in a high proportion of all the tumors (92-100%), except for B2 thymoma which showed only 45% expression. A significant increase in the expression of the MIB-1 proliferation marker (mean: 12.8% nuclear positivity) was also observed in B3 thymoma compared with the other histologic types. Statistical significance was confirmed using Kruskal's non-parameterized test for distribution. EMA was generally negative except for spindle cells in the fibrous septa in types A and AB thymoma. PAX8 showed less consistent nuclear staining than p63 and was only widely expressed in 55.7% of cases. Bcl-2 may serve as a useful marker to separate spindle cell thymomas (Type A and AB) from the other types, and the MIB1 proliferation index may be of use to differentiate type B2 from type B3 thymoma.

Myxoepithelioid tumour with chordoid features: a clinicopathological, immunohistochemical and genetic study of 14 cases of SMARCB1/INI1-deficient soft-tissue neoplasm

AIMS

Complete loss of SMARCB1/INI1 in soft-tissue tumours such as malignant rhabdoid tumour, epithelioid sarcoma, myoepithelial tumour of soft tissue and extraskeletal myxoid chondrosarcoma is often associated with high-grade malignancy and poor prognosis. The diagnosis is sometimes challenging, owing to histological similarities, so careful differential diagnosis is required. Therefore, soft-tissue tumours with complete SMARCB1/INI1 loss could potentially include an unknown entity.

METHODS AND RESULTS

We analysed 160 cases of SMARCB1/INI1-deficient soft-tissue tumour, and found 14 cases that were not classifiable into already existing categories and had common clinical and histological features. These involved two male and 12 female patients, ranging in age from 20 years to 61 years. The tumours were located in the the puboinguinal region (n = 13) and pelvic cavity (n = 1). Histologically, the tumours showed relatively uniform epithelioid to spindle-shaped cells with myxoid stroma. All tumours showed immunoreactivity for brachyury, epithelial membrane antigen, and progesterone receptor, and 12 of 14 cases did so for oestrogen receptor. Variable positive staining for α-smooth muscle actin, S100 and glial fibrillary acidic protein (GFAP) was seen. NR4A3 and EWSR1 gene rearrangements were not detected in 13 and 11 examined cases, respectively. Clinical follow-up data for the 14 patients showed that 13 were alive without disease and one had been lost to follow-up; four patients developed local recurrence and/or metastases.

CONCLUSION

The designation 'myxoepithelioid tumour with choroid features' (METC) was proposed as a tumour with intermediate malignancy controllable with appropriate treatment, including the entity of myoepithelioma-like tumour of the vulvar region. METC represents a novel and independent subset that is histologically, biologically and clinically distinct from already existing SMARCB1/INI1-deficient soft-tissue tumours.

Molecular Profiling of Clear Cell Myoepithelial Carcinoma of Salivary Glands With EWSR1 Rearrangement Identifies Frequent PLAG1 Gene Fusions But No EWSR1 Fusion Transcripts

Myoepithelial carcinoma of salivary glands is an underrecognized and challenging entity with a broad morphologic spectrum, including an EWSR1-rearranged clear cell variant. Myoepithelial carcinoma is generally aggressive with largely unknown genetic features. A retrospective review of Salivary Gland Tumor Registry in Pilsen searching for the key words "clear cell myoepithelial carcinoma," "hyalinizing clear cell," and "clear cell malignant myoepithelioma" yielded 94 clear cell myoepithelial carcinomas (CCMCs) for molecular analysis of EWSR1 rearrangement using fluorescence in situ hybridization (FISH). Tumors positive for EWSR1 gene rearrangement were tested by next-generation sequencing (NGS) using fusion-detecting panels. NGS results were confirmed by reverse-transcription polymerase chain reaction or by FISH. Twenty-six tumors originally diagnosed as CCMC (26/94, 27.6%) revealed split signals for EWSR1 by FISH. Six of these tumors (6/26, 23%) displayed amplification of the EWSR1 locus. Fifteen cases were analyzable by NGS, whereas 9 were not, and tissue was not available in 2 cases. None of the CCMCs with EWSR1 rearrangements detected by FISH had an EWSR1 fusion transcript. Fusion transcripts were detected in 6 cases (6/15, 40%), including LIFR-PLAG1 and CTNNB1-PLAG1, in 2 cases each, and CHCHD7-PLAG1 and EWSR1-ATF1 fusions were identified in 1 case each. Seven cases, including those with PLAG1 fusion, were positive for PLAG1 rearrangement by FISH, with notable exception of CHCHD7-PLAG1, which is an inversion not detectable by FISH. One single case with EWSR1-ATF1 fusion in NGS showed ATF1 gene rearrangement by FISH and was reclassified as clear cell carcinoma (CCC). In addition, another 4 cases revealed ATF1 rearrangement by FISH and were reclassified as CCC as well. Moreover, 12/68 (17%) CCMCs with intact EWSR1 gene were selected randomly and analyzed by NGS. PLAG1 fusions were found in 5 cases (5/12, 41.6%) with LIFR (2 cases), FGFR1 (2 cases), and CTNNB1 (1 case) as partner genes. Overall, PLAG1 gene rearrangements were detected in 10/38 (26%) tested cases. None of the tumors had SMARCB1 loss by immunohistochemistry as a possible explanation for the EWSR1 abnormalities in FISH. Novel findings in our NGS study suggest that EWSR1-FISH positive CCMC is a gene fusion-driven disease with frequent oncogenic PLAG1 fusions, including LIFR-PLAG1 and CTNNB1-PLAG1 in most cases. Productive EWSR1 fusions are found only in a minority of EWSR1-ATF1-rearranged cases, which were in part reclassifiable as CCCs. Detectable EWSR1-FISH abnormality in CCMCs without gene fusion perhaps represents a passenger mutation with minor or no oncologic effect.

[Primary extra-axial chondroid chordoma of the anterior nasal septum: case report of a rare chordoma with literature review]

An 87-year-old patient reported a nodular, progressively enlarging mass of the anterior nasal septum leading to partial obstruction of the nostrils. The tumor showed no infiltration of the subcutis, bone, or paranasal sinuses in imaging or intraoperatively. Histological examination revealed a chondroid tumor with lobular growth and physaliferous cell morphology. Immunohistochemistry revealed a brachyury-positive tumor without EWSR1 rearrangement, leading to the diagnosis of a chondroid chordoma. The reported case demonstrates the differential diagnostic considerations pertaining to this rare tumor, which can also have an untypical and very rare extra-axial location. Review of the literature identified 34 primary extraosseous chordomas of the nose, nasopharynx, and paranasal sinuses, and allowed the nasal chordoma presented herein to be included in this group of extra-axial chordomas.

Clinicopathologic, immunohistochemical, molecular cytogenetic profile with treatment and outcomes of 34 cases of Ewing sarcoma with epithelial differentiation, including 6 cases with "Adamantinoma-like" features, diagnosed at a single institution, India

To analyze clinicopathological features, including treatment profile of 34 cases of Ewing sarcomas with epithelial differentiation, including 6 cases with adamantinoma-like features. EWSR1 gene rearrangement was tested by fluorescence in-situ hybridization. Thirty-four tumors occurred in 19 males and 15 females (M:F = 1.26:1), with age ranging from 7 to 61 years (average = 24.2); in extremities (17), pelvis (5), paraspinal region (6), head and neck region (3), abdomen (2) and lung (1). Prior to molecular testing, 20/34(58.8%) cases were unequivocally diagnosed as Ewing sarcomas. Histopathologically, the most commonly observed pattern was nesting-type, comprising malignant round cells, including adamantinoma-like features, seen in 6 tumors. Immunohistochemically, tumor cells were diffusely positive (cytoplasmic membranous staining) for CD99/MIC2 (34/34), Fli1 (30/30); focally for synaptophysin (4/16) (25%); variably positive for AE1/AE3(31/32)(96.8%), including diffuse immunoexpression in 4 cases; EMA(6/8) and p40(3/8). All 34 (100%) tumors, tested for EWSR1 rearrangement, displayed positive results. According to the treatment details (available in 24/34 cases, 70.5%), most patients (13/24)(54.1%) were treated with surgical resection and a specific chemotherapy(CT) regimen (neoadjuvant or adjuvant settings), including 7 patients, who received adjuvant radiotherapy. During follow-up (16 cases, 47%), 5 patients developed recurrences and 8 developed metastasis, including a single, who developed recurrence. Finally, 10 patients were alive-with-disease (2-22 months); 6 free-of-disease (5-36 months). This constitutes one of the largest documentation of these rare tumors from our subcontinent, which are diagnostically challenging; require molecular confirmation and associated with treatment implications.

Meningioma-like Tumor of the Skin Revisited: A Distinct CD34+ Dermal Tumor With an Expanded Histologic Spectrum

The term meningioma-like tumor of the skin (MLTS) was coined in 1993 to designate a particular whorled spindle cell superficial cutaneous tumor. No additional confirmed cases of this entity have been reported to date. Some authors have speculated that these cases might be cellular neurothekeomas. In order to delineate the histologic spectrum and the immunophenotype of this unusual tumor, we studied 5 cases, 2 previously unreported and the 3 original cases. The immunohistochemical findings of case 5, however, were limited to those from the original study. Clinically, the tumor presented as a reddish papule, plaque, or nodule, located in the extremities or trunk. The patient often referred to a recent growth of a longstanding lesion. Histologically, the characteristic whorled spindle and stellate dendritic cell population, commonly in a perivascular arrangement, and variable myxoid component, were consistently found in all cases. A prominent microvasculature was also a constant finding. The presence of large deciduoid cells was conspicuous in one case. A reticular pattern of multivacuolated cells giving a chordoma-like appearance was evident in another case. Tumor cells were diffusely positive for CD34 in all 4 cases studied, and negative for S-100, EMA, NKI-C3, CD68, and smooth muscle markers. No complete loss of retinoblastoma protein was found. No brachyury immunostaining was found in the case with chordoid features. No EWSR1 or NAB2-STAT6 gene fusions were found. From these findings, we demonstrate that MLTS is a distinct CD34 spindle cell benign dermal tumor, unrelated to cellular neurothekeoma, and exhibiting myxoid, deciduoid, or chordoma-like features.

Metachronous Pancreatic and Thyroid Metastases from Primary Soft-Tissue Myoepithelioma in the Clavicular Region: A Case Report of a Long-Term Survivor

Patient: Male, 69-year-old

Final Diagnosis: Metachronous pancreatic and thyroid metastases from primary soft tissue myoepithelioma

Symptoms: None

Medication:—

Clinical Procedure: Surgery

Specialty: Surgery

Soft Tissue Special Issue: Myoepithelial Neoplasms of Soft Tissue: An Updated Review with Emphasis on Diagnostic Considerations in the Head and Neck

Primary myoepithelial neoplasms of soft tissue have been shown to be related to their salivary gland counterparts, with which they often share morphologic, immunophenotypic, and molecular genetic features, such as the presence of PLAG1 rearrangement in both soft tissue mixed tumor and salivary pleomorphic adenoma. However, important distinctions remain between soft tissue and salivary myoepithelial neoplasms, namely differing criteria for malignancy. This review provides an overview of the current understanding of the clinicopathologic and molecular features of soft tissue myoepithelial neoplasms, including discussion of the similarities and differences between soft tissue and salivary counterparts and relevant diagnostic issues specific to head and neck pathology practice.

Soft-Tissue Myoepithelioma of the Retroperitoneal Space Mimicking a Pancreatic Tumor: A Case Report and Literature Review

Soft-tissue myoepithelioma (STM) is an extremely rare benign tumor with predominant occurrence in head, neck, pelvic girdle and limbs. These tumors lack specific clinical and morphological features and can easily be confused with more common neoplasms. It may lead to incorrect diagnosis and management. Here, we present a clinical case of a young man with retroperitoneal STM which simulated a pancreatic tumor and required a distal pancreatectomy. Performed literature review highlights current data about clinical, morphologic, immunohistochemical and genetic evaluation, treatment and prognosis of STM.

Mesenchymal Tumors with EWSR1 Gene Rearrangements

Among the various genes that can be rearranged in soft tissue neoplasms associated with nonrandom chromosomal translocations, EWSR1 is the most frequent one to partner with other genes to generate recurrent fusion genes. This leads to a spectrum of clinically and pathologically diverse mesenchymal and nonmesenchymal neoplasms, variably manifesting as small round cell, spindle cell, clear cell or adipocytic tumors, or tumors with distinctive myxoid stroma. This review summarizes the growing list of mesenchymal neoplasms that are associated with EWSR1 gene rearrangements.

Clinicocytopathological spectrum, including uncommon forms, of nine cases of chordomas with immunohistochemical results, including brachyury immunostaining: A single institutional experience

OBJECTIVES

To present clinical and cytopathological features of nine cases of chordomas, diagnosed over 9 years and confirmed by brachyury (T) immunostaining.

METHODS

Conventional cytological smears, stained with Papanicolaou and May-Grünwald Giemsa, along with corresponding histopathological (n = 8) and immunostained sections (n = 8) were reviewed. Immunohistochemical staining was performed on tissue sections by polymer detection technique.

RESULTS

Nine tumours occurred in seven males and two females, with age ranging from 36 to 72 years (average = 58.7), in the sacrum (seven) and spine (two). On fine needle aspiration cytology, five cases were either diagnosed with or diagnosed with a suggestion of a chordoma, while three cases were diagnosed with chordoma as a differential diagnosis. On review, smears were moderately cellular, comprising myxoid stroma (9/9), epithelioid cells (9/9), physaliphorous cells (8/9), including binucleation (7/9), prominent nucleolisation (2/9), pleomorphic cells (2/9) and intranuclear inclusions (3/9). Immunohistochemically, tumour cells expressed cytokeratin (4/4), pan cytokeratin (4/4), epithelial membrane antigen (8/8), S100 protein (6/8) and brachyury (8/8). Five patients underwent surgical excision, including two who underwent adjuvant radiotherapy (RT) and four patients who underwent RT. During follow-up (n = 8), a single patient developed recurrence and another presented with metastatic lesions. Finally, five patients were alive with disease (7-53 months); a single patient was free of disease (4 months), and two patients died of disease; the latter cases displayed pleomorphic cells and intranuclear inclusions.

CONCLUSIONS

Chordomas can be primarily diagnosed by fine needle aspiration cytology in a typical clinicoradiological setting with a combination of key cytomorphological features. Pleomorphic cells and intranuclear inclusions are associated with a relatively aggressive subtype. An exact diagnosis has treatment implications and requires confirmation by brachyury immunostaining.

Myoepithelioma of the lateral abdominal wall: A case report

RATIONALE

Soft-tissue myoepithelioma is a rare neoplasm. It usually occurs in the distal or proximal extremities, but seldomly arises in the abdominal wall.

PRESENTING CONCERNS OF THE PATIENT

The patient is a 40-year-old woman who presented with a painless mass at the lateral abdominal wall for 6 months. Computed tomography scan revealed a lobulated and well-defined iso-density mass showing heterogeneously moderate enhancement. The mass exhibited intermediate T1 signal and obvious high T2 signal on magnetic resonance imaging.

INTERVENTIONS

The tumor was excised. Hematoxylin-eosin stain and immunohistochemical stain showed that the tumor was myoepithelioma.

OUTCOMES

The patient did not undergo chemotherapy and radiotherapy. No recurrence or metastasis was noted during the 1 year follow-up.

LESSONS

Radiologists should consider myoepithelioma in the differential diagnosis when finding a tumor in the abdominal wall.

Myoepithelial carcinoma or epithelioid sarcoma - A rare diagnosis with poor prognosis. A case report and review of literature

INTRODUCTION

Myoepithelial carcinoma and proximal-type epithelioid sarcoma of the vulva are two rare malignancies with known aggressive behavior. In addition to a similar clinical course, these two disease entities also have significant histologic and pathologic overlap. Given the rarity of these malignancies, there is limited literature on the appropriate treatment regimen. Nevertheless, there is a consensus that early surgical resection is beneficial in both cases.

PRESENTATION

We present a case of a patient who was initially diagnosed with myoepithelial carcinoma of the vulva with a differential later expanded to include possible epithelioid sarcoma.

DISCUSSION

We demonstrate the importance in early identification of a SMARCB1 deficiency. Additionally, we suggest an appropriate treatment regimen for these patients going forward. Specifically, we encourage consideration of bilateral superficial and deep inguinal lymphadenectomies. Furthermore, sarcoma based chemotherapy regimens in the appropriate clinical setting may be beneficial in treating SMARCB1 deficient tumors. Additionally, there are now clinical trials involving EZH2 Inhibitors which may offer benefit for similar patients going forward.

CONCLUSION

This case highlights the difficulty in making a definitive diagnosis, and the importance in identifying a SMARCB1 deficiency as it will affect treatment options and may allow for enrollment in ongoing clinical trials.

Case Reports in Oncological Medicine Myoepithelioma: A New Rearrangement Involving the LPP Locus in a Case of Multiple Bone and Soft Tissue Lesions

We report a case of multiple myoepithelioma with synchronous bone and soft tissue tumors, associated with a new genomic alteration of the LPP locus. The lesions occurred in the foot by presenting one lump in the plantar soft tissue, and three lesions were detected in the calcaneus and in the navicular bone. All tumors showed the double immunophenotype of epithelial markers and S100 protein expression. No rearrangement of the EWSR1 and FUS loci was detected as reported in myoepitheliomas. However, molecular karyotyping detected an unbalanced rearrangement of the LPP locus, not involving the HMGA2 locus, which is the most frequent translocation partner observed in benign mesenchymal tumors such as lipomas (of soft tissue as well as parosteal) and pulmonary chondroid hamartoma.

Neoadjuvant radiation therapy for the management of myoepithelial carcinoma of the upper extremity

Myoepithelial tumors of the soft tissue are a rare tumor displaying myoepithelial elements and lacking obvious ductal differentiation. The rarity of these precludes any evidence-based consensus regarding optimal management. Nevertheless, the current approach to these lesions begins with amputation or complete excision. The efficacy of neoadjuvant or adjuvant radiation therapy or chemotherapy has not been established. Here, we present the first report to the authors' knowledge of neoadjuvant radiation therapy for the treatment of this rare soft tissue neoplasm and review the management and outcomes of published cases of myoepithelial carcinoma. A patient with a soft tissue myoepithelial carcinoma that declined both amputation and chemotherapy was treated with neoadjuvant radiation therapy and wide surgical excision followed by a brachytherapy boost to the resected tumor bed. Neoadjuvant radiation therapy resulted in an excellent response with extensive treatment-related changes consisting predominantly of fibrosis, hyalinization and hemorrhage and only 10% residual viable myoepithelial carcinoma present in the surgical specimen.

Identification of SRF-E2F1 fusion transcript in EWSR-negative myoepithelioma of the soft tissue

Myoepithelial neoplasms (MN) are rare and not well-circumstanced entities displaying a heterogeneous spectrum of genetic abnormalities, including EWSR1, FUS and PLAG1 rearrangements. However, in the remaining MN no other fusion gene has been described and knowledge concerning secondary acquired molecular alterations is still poor. Therefore, we screened 5 cases of MN of the soft tissue by RNA sequencing with the aim of identifying novel fusion transcripts.

A novel SRF-E2F1 fusion was detected in two cases: one was negative for other fusions while the other showed also the presence of FUS-KLF17. The fusion was validated through independent techniques and, in both cases, SRF-E2F1 was detected only in a subclone of the tumoral mass. SRF-E2F1 maintained the coding frame, thus leading to the translation of a chimeric protein containing the DNA-binding domain of SRF and the trans-activation domain of E2F1. Moreover, ectopical expression of SRF-E2F1 demonstrated that the chimeric transcript is functionally active and could affect tumor growth.

Occurrence in two cases and biological relevance of the two genes involved suggest that the SRF-E2F1 fusion might become a helpful diagnostic tool. Further biologic studies are needed to better assess its role in MN biology.

Melanoma Masquerading as a Zosteriform Rash

BACKGROUND Primary care physicians and internal medicine specialists frequently encounter a variety of rashes. Many of these cases look and feel typical of common entities, resulting in the potential for misdiagnosis. CASE REPORT This is a case of a zosteriform rash where the surprising true diagnosis of metastatic melanoma was confirmed with bedside skin punch biopsy. Possible mechanisms involve direct cutaneous injury, neuronal, and dorsal root ganglia involvement in metastases. CONCLUSIONS Skin biopsy is indispensable especially when there is a lack of clinical response or deterioration in the clinical condition. The pathophysiology of zosteriform metastasis is unclear.

Myoepithelial carcinoma with RB1 mutation: remarkable chemosensitivity to carcinoma of unknown origin therapy

Background

Myoepithelial carcinoma of soft tissue is a rare, malignant neoplasm that is morphologically and immunophenotypically similar to its counterpart in salivary gland. It demonstrates myoepithelial differentiation, possessing both epithelial and myogenic characteristics. Thought to be chemotherapy insensitive, the optimal treatment regimen of this tumor has yet to be established and only a select few cases in the literature discuss treatment efficacy in detail.

Case presentation

Here we present a case of a young adult with metastatic myoepithelial carcinoma with an initial excellent response to systemic therapy utilizing carboplatin and paclitaxel with continued complete response after 3 years. The patient also underwent complete surgical excision and received adjuvant radiation to the primary site of disease. Exome sequencing revealed an inactivating mutation in RB1 which we believe to be the first such mutation to be reported in this cancer type.

Conclusions

Given increasing evidence suggesting RB1 loss is associated with responsiveness to conventional chemotherapies, particularly platinum-based regimens, we hypothesize that this genetic feature predisposed chemosensitivity in our patient’s tumor.

Myoepithelial Carcinoma of the Paracecal Mesentery: Aggressive Behavior of a Rare Neoplasm at an Unusual Anatomic Site

Myoepithelial tumors of the soft tissues represent a rare group of neoplasms that vary in their clinical behavior, pathologic features and genetics. They are histopathologically typified by a myoepithelial immunohistochemical phenotype, of expression of one or more epithelial markers, S100 protein and smooth muscle actin. Because of their rarity and occurrence over a wide age range and at a variety of anatomic sites, they can be difficult to diagnose due to the lack of familiarity by physicians, which is compounded by their spectrum of histologic features and morphologic overlap with several other neoplasms. Recent genetic insights have aided classification, and it is increasingly understood that soft tissue myoepithelial neoplasms can be stratified into two distinct morphologic and genetic subgroups. We describe a case of a 44-year-old man who was diagnosed with a primary myoepithelial neoplasm of the paracecal mesentery, which showed aggressive local recurrence after four years. The tumor was composed of cords of ovoid cells within chondromyxoid stroma, and displayed a characteristic pancytokeratin, S100 protein and smooth muscle actin-positive myoepithelial immunoprofile. Primary myoepithelioma has not been previously described at this site, and this case highlights this varied family of tumors, emphasizes the need to consider myoepithelial tumor in the differential diagnoses of carcinoma variants occurring in the bowel or mesentery, and also adds to the number of reported myoepithelial neoplasms showing markedly aggressive behavior.

Soft Tissue Myoepithelial Carcinoma of the Neck with Spinal Invasion

Soft tissue myoepithelial neoplasms are a rare yet diverse group of tumors, ranging from benign to malignant lesions. Their presentation in the head and neck region is uncommon and represents a challenging diagnosis. Early identification of myoepithelial carcinoma is crucial given its more aggressive course compared to its benign counterpart, although the histopathological distinction between the two can be difficult. EWSR1 gene rearrangement is found in half the cases and has a speculative role in pathogenesis. Complete excision remains the treatment of choice. The roles of chemotherapy and radiation are unclear. We report the hospital course of a 33-year-old female who presented to our institution with a posterior neck mass with spinal invasion, diagnosed as myoepithelial cancer. A literature review of these rare tumors is discussed here.

Primary intra-osseous myoepithelioma of phalanx mimicking an enchondroma

Myoepitheliomas (MEs) are uncommon tumours of the soft tissue with an intermediate biological behaviour and uncertain differentiation. Primary intra-osseous MEs are rare and occur predominantly in the axial and proximal appendicular skeleton in middle-aged patients. The morphological variation of the tumour cells and stromal metaplasia may cause considerable diagnostic confusion, especially when it occurs in an unusual location. A wide panel of immunohistochemical markers is required to exclude other histological mimics. A 37-year-old male presented with a recurrent swelling in the right middle finger for 1-month duration. Radiographic images showed an expansile, lytic, intra-osseous lesion with high signal intensity on T2W fat-suppressed MR images in the proximal phalanx of the right middle finger without cortical breach, highly suggestive of an enchondroma. Histopathology revealed a lobulated tumour comprising of polygonal to spindle cells in groups and cords in a chondromyxoid stroma. No cellular atypia was noted. The tumour cells were immunopositive for epithelial membrane antigen (EMA), p63, S100 and smooth muscle actin (SMA), compatible with the diagnosis of an intraosseous ME. The proximal phalanx of the right middle finger was excised, revealing a similar tumour, and the patient has been on regular follow-up for the last 18 months without any recurrence. Primary intra-osseous MEs are extremely rare, and this is the second reported occurrence in small bones. A differential diagnosis of ME should be kept for enchondroma-like lesions of the bone for proper histopathological assessment and accurate diagnosis. Documentation of such cases and follow-up will enhance our understanding of their clinical course and prognosis.

Expanding the Spectrum of Renal Tumors in Children: Primary Renal Myoepithelial Carcinomas With a Novel EWSR1-KLF15 Fusion

We report the first 2 examples of primary renal myoepithelial carcinoma (MEC), both occurring in children. Both tumors had the unique morphologic features, immunophenotype, and EWSR1 gene rearrangements supporting the diagnosis. In keeping with the previous observations of an aggressive behavior in pediatric MEC, both cases presented with advanced local stage and distant metastases at the time of diagnosis. The EWSR1 translocation partner was identified as the Kruppel-like factor 15 (KLF15) gene in both tumors, and the novel EWSR1-KLF15 gene fusion transcripts were verified using reverse transcription polymerase chain reaction and Sanger dideoxy sequencing. So far, a role for KLF15 in carcinogenesis has not been established, in contrast to other members of the Kruppel-like family of transcription factors, and no rearrangements involving this gene have been documented to our knowledge. These findings expand the spectrum of pediatric renal tumors to include MEC. The characterization of novel EWSR1-KLF15 fusion transcripts carries important diagnostic implications, as well as clues to understand the pathogenesis of these neoplasms.

Myoepithelioma of Soft Tissues: A Single Institution Retrospective Case Series

BACKGROUND

Myoepithelioma of the soft tissues is a rare entity and little is known about how best to manage locally recurrent and high-grade disease. Here, we retrospectively examined outcomes of surgery, chemotherapy, and radiation therapy (RT) for treatment of low-grade and high-grade myoepithelioma of soft tissues.

METHODS

We reviewed 20 cases of myoepithelioma of soft tissues seen at Mayo Clinic between 1994 and 2014. The effect of histologic grade and therapies received on relapse and survival were assessed.

RESULTS

We identified 13 patients with low-grade disease and 7 patients with high-grade disease. We found that low-grade disease was frequently effectively managed with surgical resection alone, whereas high-grade disease frequently metastasized and was often fatal. The 5-year event-free survival was 88% (confidence interval, 46%-98%) for low-grade disease versus 36% (confidence interval, 7%-75%; P=0.04) for high-grade disease. The relapse rate in low-grade disease was 29% at 5 years versus 64% (P=0.04) in high-grade disease. No significant responses to chemotherapy were noted, however, excellent responses to perioperative RT were seen.

CONCLUSIONS

Surgery continues as the primary modality of treatment for myoepithelioma of soft tissues. Our study did not show a clear benefit of chemotherapy in the metastatic disease setting, but supports the use of perioperative RT in the management of high-grade disease; further investigation is warranted.

Soft Tissue Myoepithelial Carcinoma in a Child: Case Report

BACKGROUND

Myoepithelial carcinoma was only recently recognized to occur primarily in soft tissue. Only a small number has been reported in children.

OBSERVATION

We report a rare case of myoepithelial carcinoma of the leg in a 4-month-old boy with a good response to chemotherapy initially. However, he presented secondarily during chemotherapy a local and metastatic progression.

CONCLUSIONS

The rarity of the tumor and unusual age of discovery have prompted us to report this case. Our case suggests that this disease can have an aggressive behavior. This is why we advise a rapid and correct diagnosis followed by an aggressive treatment.

Soft Tissue Myoepithelial Carcinoma Metastatic to the Cecum: Highlighting an Unusual Metastatic Pattern and the Need for Diagnostic Awareness

Myoepithelial neoplasms of the soft tissues are a rare, heterogeneous group of tumors for which classification continues to evolve. While well defined within salivary glands, they can also arise in viscera and soft tissues, where diagnosis is challenging due to the lack of clinical and pathological familiarity. We present the case of a 36 year old man with myoepithelial carcinoma arising as a primary tumor within the soft tissues of the neck, which metastasized to the cecum, causing intussusception. This spindle cell neoplasm showed the classic S100 protein, smooth muscle actin and pancytokeratin-positive immunoprofile. Metastasis of myoepithelial carcinoma to the cecum has not been previously described, and coupled with the spindle cell morphology, may cause significant diagnostic difficulty in the absence of clinical familiarity, particularly as there is morphologic overlap with spindle cell neoplasms arising more commonly in gastrointestinal sites, including gastrointestinal stromal tumor, leiomyosarcoma and sarcomatoid carcinoma.

Clinicopathological features of five unusual cases of intraosseous myoepithelial carcinomas, mimicking conventional primary bone tumours, including EWSR1 rearrangement in one case

Primary intraosseous myoepithelial tumours, including carcinomas are rare tumours. The concept of histopathological spectrum of these tumours is evolving. We describe clinicopathological and immunohistochemical features of five myoepithelial carcinomas, including molecular cytogenetic results in one case. There were five male patients within age-range of 8-40 years (median = 26). Four tumours occurred in the long bones, including two tumours, each, in the femur and fibula, respectively, while a single tumour occurred in the proximal phalanges. Tumour size (n = 3 cases) varied from 5.6 to 8.6 cm. On radiological imaging, most tumours appeared as expansile, lytic and destructive lesions. Two tumours appeared as sclerotic lesions. Two cases were referred with diagnoses of chondrosarcomas and a single case was referred with two different diagnoses, including an adamantinoma and an osteosarcoma. Histopathological examination in all these cases showed multinodular tumours comprising mostly polygonal cells, exhibiting moderate nuclear atypia and interspersed mitotic figures within a stroma containing variable amount of myxoid, chondroid, hyalinised and osteoid-like material. Three tumours revealed prominent squamous differentiation. By immunohistochemistry, tumour cells were positive for EMA (5/5), pan CK (AE1/AE3) (3/3), CK5/6 (4/4), CK MNF116 (1/1), S100 protein (5/5) and GFAP (3/5). The first tumour revealed EWSR1 rearrangement. The first patient, 10 months after tumour resection and a simultaneous lung metastatectomy, is free-of-disease (FOD). The second patient, 11 months after tumour resection is FOD. The third and fourth patients underwent wide resections and are on follow-up. The fifth patient underwent resections, including a lung metastatectomy. Primary intraosseous myoepithelial carcinomas are rare and mimic conventional primary bone tumours. Some primary intraosseous myoepithelial carcinomas display EWSR1 rearrangement. Squamous differentiation may be considered as an addition to their evolving histopathological spectrum. Immunohistochemical stains constitute as a necessary tool for arriving at the correct diagnosis in such cases, which has treatment implications. Surgical resection remains the treatment mainstay.

Epithelioid Sarcoma: Diagnostic Features and Genetics

Epithelioid sarcoma (ES) is a rare, aggressive soft-tissue neoplasm of uncertain differentiation, characterized by nodular aggregates of epithelioid cells, which are immunoreactive to cytokeratins (CKs) and epithelial membrane antigen, and often for CD34. It has a propensity for multifocal disease at presentation, local recurrence, and regional metastasis. These are aggressive neoplasms with particularly poor prognosis after regional or distant metastatic disease, for which surgical resection is still the mainstay of treatment, and options for patients with metastatic disease remain undefined. There are 2 distinct variants: classic ES, which typically presents as a subcutaneous or deep dermal mass in the distal extremities of young adults and comprises nodular distributions of relatively uniform epithelioid cells with central necrosis, and the proximal variant, which has a predilection for proximal limbs and limb girdles and the midline of the trunk, which is composed of sheets of larger, more atypical cells with variable rhabdoid morphology. Both classic and proximal-type ESs are associated with the loss of SMARCB1/INI1 protein expression, but appear otherwise molecularly relatively heterogeneous. We review classic and proximal-type ES, discussing morphology, immunohistochemical and genetic findings, the differential diagnosis, and the future potential for targeted therapies.

Fine-needle aspiration of soft tissue myoepithelioma

Soft tissue myoepithelioma is a rare neoplasm composed of myoepithelial cells. We describe the cytologic features of a soft tissue myoepithelioma arising in the right lower chest wall in a 65-year-old woman. The fine-needle aspiration (FNA) smears showed round to oval, spindle, epithelioid, and plasmacytoid cells in the myxoid background. The nuclei were uniform, round to ovoid, with finely distributed chromatin and eosinophilic or pale cytoplasm, and resembled lobular carcinoma of breast. Ultrasound guided core biopsy showed the tumor cells had bland cytologic features, arranged in small cords, nests, and dissociated single cells, with no glandular differentiation or breast tissue seen. The tumor cells demonstrated immunoreactivity for cytokeratin (AE1/AE3) and glial fibrillary acidic protein, but were negative for estrogen receptor. Fluorescence in situ hybridization demonstrated the EWSR1 rearrangement, confirming the diagnosis of myoepithelioma.

Ossifying fibromyxoid tumor: morphology, genetics, and differential diagnosis

Ossifying fibromyxoid tumor (OFMT) is a soft tissue neoplasm of uncertain differentiation and intermediate (rarely metastasizing) biologic potential, with typical morphologic features, of an encapsulated, lobulated tumor comprising uniform polygonal cells within fibromyxoid stroma, which is surrounded by or contains metaplastic bone, classically as a peripheral rim of lamellar bone. Ossifying fibromyxoid tumor can arise at almost any site, although most frequently occurs within the extremities and trunk. Although most behave in a benign fashion, tumors can rarely show atypical or malignant features. It is now established that OFMTs represent translocation-associated tumors, with up to 85% associated with recurrent gene rearrangements, mostly involving the PHF1 gene (including in typical, atypical, and malignant neoplasms), with EP400-PHF1 in approximately 40% of tumors, and ZC3H7B-BCOR, MEAF6-PHF1, and EPC1-PHF1 fusions also described. Correct diagnosis is clinically important to ensure correct treatment and prognostication, both to avoid overdiagnosing OFMT as a malignant neoplasm such as osteosarcoma and also because of the propensity for aggressive behavior in a small number of OFMT. We review OFMT, with emphasis on the morphologic spectrum, recent molecular genetic findings, and the differential diagnosis.

Ancillary molecular analysis in the diagnosis of soft tissue tumours: reassessment of its utility at a specialist centre

Aims

The histological diagnosis of soft tissue tumours (STTs) can be difficult, sometimes requiring a combination of morphology, immunophenotype and ancillary molecular tests. Many STTs are associated with characteristic genetic aberrations that can be assessed using fluorescence in situ hybridisation (FISH), reverse transcription-PCR (RT-PCR) or mutational analysis. We have previously assessed the practicality and sensitivity of using these modalities as part of the routine diagnosis of STT in paraffin-embedded material and now revisit the subject in light of further experience in this field.

Methods

200 consecutive cases from 2013 that had undergone FISH, RT-PCR or mutational analysis were assessed to evaluate their diagnostic utility compared with preliminary histological assessment.

Results

218 FISH, 91 RT-PCR and 43 mutational analysis tests were performed. Compared with the previous study, FISH for MDM2 amplification in possible well-differentiated/dedifferentiated liposarcomas, and mutational analysis for assessing KIT, PDGFR and BRAF mutations made up a large proportion of the workload (107 and 43 tests, respectively). As in the previous study, alveolar rhabdomyosarcoma showed the best FISH:RT-PCR concordance. Unlike previously, RT-PCR showed marginally higher sensitivity than FISH (78.9% and 76.9%), while continuing to demonstrate higher specificity (90.9% and 84.3%). RT-PCR again showed an increased failure rate (5.5%; 1% for FISH).

Conclusions

We demonstrate the continuing utility of RT-PCR and FISH for STT diagnosis, and that each has advantages in specific contexts. These ancillary molecular tests are important tools in both defining and excluding diagnoses of STT, which is crucial in determining prognosis and guiding appropriate management.

Myoepithelial Tumors: An Update

Primary myoepithelial neoplasms of soft tissue are uncommon, and have been increasingly characterized by clinicopathologic and genetic means. Tumors are classified as mixed tumor/chondroid syringoma, myoepithelioma, and myoepithelial carcinoma, and they share morphologic, immunophenotypic, and genetic features with their salivary gland counterparts. However, soft tissue myoepithelial tumors are classified as malignant based on the presence of cytologic atypia, in contrast to the criterion of invasive growth in salivary gland sites. This review discusses the clinicopathologic and morphologic characteristics, distinct variants, and currently known genetic alterations of myoepithelial neoplasms of soft tissue, skin, and bone.

A large mediastinal benign myoepithelioma effacing the entire hemithorax: case report with literature review

Background

Myoepithelial neoplasms, although sometimes encountered in soft tissues are described very rarely in mediastinum and lung. We reported a rare case of such a tumor which was very large in size and not connected to respiratory tree.

Case presentation

A 24 year old male presented with blunt chest pain and respiratory distress. A CT scan was performed which showed large heterogeneously enhancing soft tissue mass occupying the left hemithorax. It measures 18.5 X 15.8 X 7.6. Thoracotomy with excision of the tumor was done. Operative findings include multilobulated and nodular large glistening white tumor located in anterior mediastinum adherent to parietal pleura and effacing the pulmonary parenchyma. However tumor was not connected or seems to originate from trachea or lung. Microscopic sections show neoplastic lesion composed of nests, cords and trabeculae of small to medium sized cells with round nuclei and clear cytoplasm. Background showed myxoid appearance with areas of cartilaginous differentiation. Immunohistochemical expression of CKAE1/AE3, p63, ASMA, S100 and GFAP favored the diagnosis of benign myoepithelioma.

Conclusion

Myoepithelial tumors are rare soft tissue tumors thought to arise from stem cells capable of divergent differentiation and occur anywhere in the body. Histopathologic recognition of these tumors is essential as these tumors may behave in a benign fashion despite large sizes.