Myoepithelial tumors of soft tissue: a clinicopathologic and immunohistochemical study of 101 cases with evaluation of prognostic parameters

Effect of Primary Site and Treatment Modality of Patients With Head and Neck Myoepithelial Carcinoma on Survival

AIM

Epidemiological evidence on myoepithelial carcinoma is rare. This study aimed to investigate the effect of tumor primary site and treatment modality on survival in patients with head and neck myoepithelial carcinoma.

MATERIALS AND METHODS

Data on adult patients diagnosed with head and neck myoepithelial carcinoma between 2000 and 2019 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Uni- and multivariable Cox proportional hazard models were utilized to evaluate the effects of different tumor primary sites and treatment modalities on overall survival (OS) and cancer-specific survival (CSS), and expressed as hazard ratio (HR) and 95% confidence interval (CI).

RESULTS

A total of 415 patients were enrolled. No significant differences in OS and CSS were found between different tumor primary sites (P > 0.05). Compared with partial excision, patients with total excision (HR = 1.65, 95%CI: 1.12-2.42) (partial or total removal of the organ in which the tumor is located and complete removal of the tumor) or no surgery (HR = 3.52, 95%CI: 2.05-6.03) had worse OS. Compared with surgery only, patients with radiotherapy only had poorer OS (HR = 4.69, 95%CI: 2.32-9.46) and CSS (HR = 6.72, 95%CI: 2.59-17.46), while no significant differences in OS (P = 0.120) and CSS (P = 0.847) were found among patients who received surgery combined with radiotherapy. In patients with AJCC III/IV, patients with radiotherapy only (HR = 4.51, 95%CI: 1.61-12.62) had poorer OS compared to those with surgery only, whereas patients who received surgery combined with radiotherapy had better OS (HR = 0.50, 95%CI: 0.29-0.89).

CONCLUSION

The tumor primary site may not affect the prognosis of patients with myoepithelial carcinoma, while the effect of treatment modality on prognosis is related to the primary site and stage of the tumor.

Myoepithelial tumors of soft tissue and bone in children and young adults: A clinicopathologic study of 40 cases occurring in patients ≤ 21 Years of age

Myoepithelial tumors of the soft tissue and bone occurring in patients 21 years of age and younger are rare, and their clinicopathologic features remain incompletely understood. We studied a well-characterized series of 40 such tumors. Cases were retrieved from our archives for the period 2009-2022 and re-reviewed. Available immunohistochemical and molecular genetic data was collected. Clinical information including available follow-up was obtained. The tumors occurred in 18 males and 22 females, ranging from 3 months to 21 years of age (median 11.5 years), and involved a wide variety of soft tissue (n = 36) and bone (n = 4) locations. Histologically benign myoepithelial tumors tended to occur in adolescents (median age 14.5 years; range 5-21 years), whereas myoepithelial carcinomas occurred in younger patients (median age 8.5 years; range 3 months-20 years). Microscopically, the tumors showed a complex admixture of epithelioid, plasmacytoid and spindled cells in a variably hyalinized, myxoid, chondroid or chondromyxoid background. Small subsets of histologically malignant tumors had rhabdoid or "round cell" features. Immunohistochemistry showed 35/40 (88%) cases to be positive with at least one keratin antibody. The 5 keratin-negative tumors were uniformly positive for S100 protein and/or SOX10 and expressed EMA (4 cases) and/or p63 (3 cases). EMA, SMA and GFAP were positive in 21/25 (84%), 13/21 (62%), and 8/21 (38%) tumors, respectively. SMARCB1 and SMARCA4 expression was retained in 29/31 (94%) and 22/22 (100%) of cases, respectively. FISH for EWSR1 gene rearrangement was positive in 6/18 (33%) tested cases. Two EWSR1-negative tumors were also FUS-negative. NGS identified EWSR1::POU5F1, FUS::KLF17, and BRD4::CITED1 gene fusions in 3 tested cases. Clinical follow-up (22 patients; median 23 months; range 1-119 months) showed 3 patients with local recurrences and 5 with distant metastases (lymph nodes, lung, and brain). Three patients died of disease, 3 were alive with recurrent or unresectable disease, and 16 were disease-free. Adverse clinical outcomes were seen only in patients with malignant tumors. We conclude that myoepithelial neoplasms of soft tissue and bone are over-repesented in patients ≤21 years of age, more often histologically malignant, and potentially lethal. Histologic evaluation appears to reliably predict the behavior of these rare tumors.

Fine-needle aspiration cytology of retroperitoneal myoepithelial carcinoma: A rare encounter with diagnostic dilemmas

Myoepithelial carcinoma (MC) arises from the myoepithelial cells. It is a rare tumor with a predilection for salivary glands. MC in soft tissue is uncommon. Soft tissue MC exhibits dual epithelial and smooth muscle phenotype. The extremities and limb girdles are commonly affected. We present cytological findings of retroperitoneal MC with an accurate diagnosis being rendered with the aid of immunocytochemistry on the cell block and demonstration of EWSR1 rearrangements by fluorescence in situ hybridization on cytology smear. The smears were cellular, showing loose clusters and sheets of tumor cells embedded in dense eosinophilic to myxoid matrix material. The cells were oval to polygonal, with focal areas showing moderate nuclear pleomorphism, vesicular to coarse chromatin, and vacuolated cytoplasm with clearing. On immunocytochemistry, tumor cells were positive for epithelial membrane antigen, pan-cytokeratin, calponin, smooth muscle actin, and S-100. A literature review shows only a handful of cases of soft tissue MC. The current report emphasizes the need for cytomorphological awareness with the employment of ancillary testing for accurately diagnosing this rare tumor at an uncommon location. We also discuss the diagnostic challenges and troubleshooting.

Myoepithelial Tumors of Bone With EWSR1::PBX3 Fusion: A Spectrum From Benign to Malignant

The EWSR1::PBX3 fusion gene, commonly associated with cutaneous syncytial myoepitheliomas, is also found in myoepithelial tumors (METs) of bone and soft tissue. These tumors typically demonstrate benign histology and favorable outcomes. This study examines 6 previously unreported intraosseous METs harboring the EWSR1::PBX3 fusion, focusing on their histopathologic characteristics, immunophenotype, clinical and radiographic profiles, and patient outcomes. The cohort comprised 5 men and 1 woman, aged 25 to 65 years (median age: 31 years), with tumors located in the proximal tibia (3 cases), distal radius (2 cases), and ilium (1 case) and sizes between 3.2 and 12.2 cm (median size: 3.9 cm). Imaging showed osteolytic lesions with varying degrees of cortical involvement and soft tissue extension in 3 cases. Histologically, 4 tumors showed mainly uniform oval-to-spindled cells in syncytial or fascicular arrangements within a collagenous matrix, displaying either bland nuclear features or mild atypia, and low to slightly elevated mitotic activity (≤1 per 10 high-power fields in 3 cases and 6 per 10 high-power fields in 1), classifying them as benign or atypical METs. In contrast, 2 tumors exhibited pronounced nuclear atypia with ovoid, spindled, epithelioid and round cells, hyperchromatic nuclei, inconspicuous nucleoli, increased N/C ratios, high mitotic rates (17 and 19 per 10 high-power fields), and extensive necrosis. Both tumors behaved aggressively-one patient underwent amputation after neoadjuvant chemotherapy and radiation, and the other died within 7 months with the disease still present. Immunohistochemically, the tumors consistently expressed epithelial membrane antigen and S100 but lacked keratin (AE1/AE3) expression. Our study demonstrated that bone METs with EWSR1::PBX3 fusions encompass a histologic continuum from benign to malignant, with benign/atypical METs mirroring their cutaneous analogs in morphology, and malignant variants distinguished by heterogeneous cytologic and architectural features, pronounced nuclear atypia, and high mitotic rates.

Molecular analysis of apocrine mixed tumors and cutaneous myoepitheliomas: a comparative study confirming a continuous spectrum of one entity with near-ubiquitous PLAG1 and rare mutually exclusive HMGA2 gene rearrangements

Myoepithelial neoplasms of the skin and soft tissue still represent a confusing and somewhat controversial field in pathology as it appears that this category includes several different entities. However, recent studies have suggested that both apocrine mixed tumors (AMT) and cutaneous myoepitheliomas (CM) harbor identical chromosomal rearrangements involving the PLAG1 gene and hence may represent a morphological spectrum. The aim of the present study was to share our institutional experience with these tumors and specifically focus on studying their immunohistochemical and molecular features to further assess their relatedness. Eleven cases of AMT and 7 cases of CM were collected and analyzed using immunohistochemistry (IHC), PLAG1 FISH, and Archer FusionPlex assay. There were 14 male and 4 female patients with ages ranging from 26 to 85 years (median 55.8 years, mean 58.5 years). AMTs were mainly located in the head and neck (n = 10), while CMs were mainly located in the acral sites (n = 5). PLAG1 IHC was diffusely strongly positive in 14/17 (82%) cases, whereas a single case of AMT diffusely expressed HMGA2. Both tumor groups showed PLAG1 gene fusions which were detected in 6/13 analyzable samples (AMT, n = 4 and CM, n = 2), and included TRPS1::PLAG1 (n = 3), NDRG1::PLAG1 (n = 1), CTNNB1::PLAG1 (n = 1) and a novel PXDNL::PLAG1 fusion (n = 1). The remaining 5 cases were negative, 5 were not analyzable and the single case positive for HMGA2 by IHC revealed a potential HMGA2 gene rearrangement. The cases were further studied by FISH, with 12/17 cases showing PLAG1 gene rearrangement (AMT, n = 8 and CM, n = 4). Altogether, 14/18 cases showed PLAG1 gene rearrangement by at least one of the methods. PLAG1 immunohistochemistry had a 92% specificity and sensitivity. Our study provided additional data to suggest that AMT and CM share overlapping morphological and immunohistochemical features as well as molecular background characterized by PLAG1 gene fusions and thus represent a morphological spectrum. In addition, we identified a novel PXDNL::PLAG1 fusion and suggested that rare cases may harbor HMGA2 gene alterations which seem to be mutually exclusive with PLAG1 gene fusions. The relatedness of these tumors to salivary gland myoepithelial neoplasms and distinctness from eccrine mixed tumors and other skin and soft tissue myoepithelial neoplasms with EWSR1/FUS fusions is discussed.

Updates on WHO classification for small round cell tumors: Ewing sarcoma vs. everything else

The WHO Classification of Soft Tissue and Bone Tumours currently recognizes four categories of undifferentiated small round cell sarcoma: Ewing sarcoma, round cell sarcoma with EWSR1-non-ETS fusions including NFATc2 and PATZ1, CIC-rearranged sarcoma, and sarcoma with BCOR genetic alterations. These neoplasms frequently pose significant diagnostic challenges due to rarity and overlapping morphologic and immunohistochemical findings. Further, molecular testing, with accompanying pitfalls, may be needed to establish a definitive diagnosis. This review summarizes the clinical, histologic, immunohistochemical, and molecular features of these neoplasms. In addition, differential diagnosis and areas of uncertainty and ongoing investigation are discussed.

Histological and imaging features of myoepithelial carcinoma of the bone and soft tissue

OBJECTIVE

To depict histological and imaging features of myoepithelial carcinoma of the bone and soft tissue.

MATERIALS AND METHODS

We retrospectively examined histological features in 22 patients with myoepithelial carcinoma of the bone (4 patients) and soft tissue (18 patients) at a single institution. Imaging analysis of 15 patients (bone, 3 patients; soft tissue, 12 patients;) with preoperative images involved classifying lytic bone lesions via the modified Lodwick-Madewell classification; the growth patterns of soft tissue lesions were classified as well-defined, focally invasive, or diffusely invasive.

RESULTS

Local recurrence occurred in eight out of 22 patients (36.3%). Four of 22 patients (18.2%) had metastasis at presentation, whereas 11 of 22 patients (50.0%) had distant metastasis during follow-up. Severe cytological pleomorphism was observed in 14 of 22 patients (63.6%), and 10 of 22 tumors (45.5%) showed ≥ 10 mitoses/10 high-power fields. Vascular invasion was observed in 10 of 22 patients (45.5%). Extracapsular/extraskeletal infiltration into the surrounding tissues was assessed in 20 patients, with 14 of them (70%) showing infiltration beyond the tumor border. Regarding imaging of bone lesions, two patients had Ludwick type IIIB, whereas one patient had type II. The growth pattern of soft tissue lesions was well-defined in two patients (16.7%), focally invasive in seven patients (58.3%), and diffusely invasive in three (25.0%) out of 12 patients.

CONCLUSION

Myoepithelial carcinoma of the bone and soft tissue presents high risk of local recurrence and distant metastasis. Histological and imaging features might be important to understand the aggressive behavior of the tumor.

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.

Myoepithelial Carcinoma of Soft Tissue: Report of Two Cases

CASE

A 40-year-old man was evaluated for a painful mass on his right calf, and a 36-year-old woman presented with a painless mass on her right foot. Final pathology revealed marked nuclear atypia and positivity for S100/SOX10 and AE1/AE3 confirming diagnoses of myoepithelial carcinoma. Both patients underwent surgical resection and are without evidence of local recurrence or metastatic disease at 1-year follow-up.

CONCLUSION

Soft-tissue tumors presenting in the extremities warrant careful evaluation and timely histopathologic diagnosis. Myoepithelial carcinomas are rare, aggressive tumors with a propensity for local recurrence and metastasis. Treatment of these tumors should be discussed by a multidisciplinary tumor team.

Sarcomas with EWSR1::Non-ETS Fusion (EWSR1::NFATC2 and EWSR1::PATZ1)

The wide application of increasingly advanced molecular studies in routine clinical practice has allowed a detailed, albeit still incomplete, genetic subclassification of undifferentiated round cell sarcomas. The WHO classification continues to include provisional molecular entities, whose clinicopathologic features are in the early stages of evolution. This review focuses on the clinicopathologic, molecular, and prognostic features of undifferentiated round cell sarcomas with EWSR1/FUS::NFATC2 or EWSR1::PATZ1 fusions. Classic histopathologic findings, uncommon variations, and diagnostic pitfalls are addressed, along with the utility of recently developed immunohistochemical and molecular markers.

Clinicopathological Features of Three Rare EWSR1::NFATC2 Sarcomas of Bone and Soft Tissues

Certain undifferentiated round cell sarcomas displaying EWSR1::NFATC2 fusion have recently been reported, mostly in the bones. This report presents clinicopathological features of 3 additional EWSR1::NFATC2 fusion sarcomas of bone and soft tissues. We present 2 soft tissue and 1 bone tumors: A 62-year-old man with pain and a slowly growing, 8-cm-sized soft tissue mass in the anterolateral compartment of his right calf, along with multiple pulmonary metastatic lesions; a 63-year-old man with a 5-cm sized axillary mass of 4 months duration and a cystic renal mass; and a 53-year-old man with a complaint of leg pain was found to have a 2-cm diameter, intramedullary, lytic mass in the diaphysis of his left femur. Microscopic examination of the tumors in all patients revealed round to epithelioid cells arranged in cords and trabeculae in a myxohyaline stroma. Immunohistochemically, the tumor cells were positive for MIC2/CD99 (3/3), EMA (3/3), NKX3.1 (3/3), NKX2.2 (2/2), CD10 (2/2), and aggrecan (1/1), while negative for S100P and GFAP. Various keratins were also negative except focal AE1/AE3 positivity in the third tumor. By fluorescence in-situ hybridization, 2 tumors (#1 and #3) revealed EWSR1 gene rearrangement and amplification. Furthermore, 2 tumors (#1 and #2) displayed EWSR1ex8::NFATC2ex3 fusion with next-generation sequencing (NGS). The first patient was offered chemotherapy. However, he died of pulmonary metastasis. This report highlights the value of combining histopathological features and immunostains such as NXK3.1, NKX2.2, CD10, and aggrecan, along with EWSR1 testing for triaging these tumors for rare gene fusions by NGS that has prognostic implications.

SMARCB1/INI1-deficient epithelioid and myxoid neoplasms in paratesticular region: Expanding the clinicopathologic and molecular spectrum

SMARCB1/INI1-deficient soft tissue tumors with epithelioid and myxoid features are diverse and mainly include soft tissue myoepithelial tumor, extraskeletal myxoid chondrosarcoma, and the recently described myoepithelioma-like tumor of the vulvar region and myxoepithelioid tumor with chordoid features. Because of their overlapping features, the accurate diagnosis and classification of these tumors are often challenging. Herein, we report two unique cases of SMARCB1/INI1-deficient soft tissue neoplasm with epithelioid and myxoid features occurring in male paratesticular region. The first case was a 52-year-old man presented with an intermittent painful left paratesticular mass for 1 year. The second case was a 41-year-old man presented with a painless paratesticular mass on the right side for 3 months. Both patients underwent an orchiectomy. After 6 and 26 months of follow-up, both were alive with no evidence of recurrence or metastasis. In both cases, the tumor was relatively well-demarcated and showed monomorphic round to epithelioid cells arranged in a nested, trabecular, reticular, and corded pattern, setting in a myxohyalinized and vascularized matrix. The tumor cells showed relatively uniform round nuclei with vesicular chromatin and variably prominent nucleoli. No rhabdoid cells were identified. Mitoses numbered 3 and 2 per 10 high-power fields. Tumor necrosis or lymphovascular invasion was absent. Immunohistochemically, both tumors expressed epithelial membrane antigen (focal), calponin (focal), and CD99. SMARCB1/INI1 expression was deficient in both cases. In addition, case 1 diffusely expressed pan-cytokeratin, and case 2 diffusely expressed CD34 and synaptophysin. Molecular genetically, case 1 showed SMARCB1 homozygous deletion as detected by fluorescence in-situ hybridization (FISH), and case 2 demonstrated SMARCB1 copy number deletions by next-generation sequencing and SMARCB1 monoallelic deletion by FISH. Both cases lacked EWSR1 rearrangements by FISH. The overall clinicopathologic profiles of the two cases made it difficult to classify them as one of the established categories of SMARCB1/INI1-deficient mesenchymal tumors. Our study further expands the clinicopathologic and molecular spectrum of SMARCB1/INI1-deficient epithelioid and myxoid neoplasms and highlights the challenges to diagnose these tumors.

A Practical Approach to Small Round Cell Tumors Involving the Gastrointestinal Tract and Abdomen

Small round cell neoplasms are diagnostically challenging owing to their clinical and pathologic overlap, necessitating use of large immunopanels and molecular analysis. Ewing sarcomas (ES) are the most common, but EWSR1 is translocated in several diverse neoplasms, some with round cell morphology. Molecular advances enable classification of many tumors previously termed 'atypical ES'. The current WHO Classification includes two new undifferentiated round cell sarcomas (with CIC or BCOR alterations), and a group of sarcomas in which EWSR1 partners with non-Ewing family transcription factor genes. This article reviews the spectrum of small round cell sarcomas within the gastrointestinal tract and abdomen.

Spindle-cell myoepithelioma: A rare case in a finger of a 15-year-old boy

Cutaneous myoepithelioma is a rare neoplasm of the skin that has become more widely recognized in recent years despite significant diagnostic pitfalls. It is a benign neoplasm with a high recurrence rate if not excised radically, and must be distinguished from its malignant counterpart. Few cases have been described so far and, to our knowledge, no cases in the finger of a child exist in the literature. We report the case of a 15 year-old boy affected by a rare form of locally aggressive spindle-cell myoepithelioma, and suggest a new multidisciplinary approach combining surgical excision and custom brachytherapy.

[Myoepithelial tumors of soft tissue: A case of mixed tumor]

Myoepithelial neoplasms of soft tissue represent a rare entity which has been described only recently when compared to salivary gland tumors with whom they share histopathological and molecular features. The most common locations are the superficial soft tissues of the limbs and limb girdles. However, they can rarely occur in the mediastinum, abdomen, bone, skin and visceral organs. Benign forms (myoepithelioma and mixed tumor) are more frequent than myoepithelial carcinoma and the latter mostly affects children and young adults. Diagnosis is mainly based on histology, which shows a proliferation of myoepithelial cells of variable morphology with or without glandular structures in a myxoid background, and immunohistochemistry, which shows co-expression of epithelial and myoepithelial markers. Molecular tests are not mandatory, but in selected cases FISH analysis can prove useful as about 50% of myoepitheliomas show EWSR1 (or rarely FUS) rearrangements and mixed tumors show PLAG1 rearrangements. Here, we present a case of a mixed tumor of the soft tissue occuring in the hand with expression of PLAG1 in immunohistochemistry.

Myoepithelial carcinoma of soft tissues and bone

AIM

Myoepithelial carcinoma occurs mainly in salivary glands but rarely can also occur in soft tissues or bone. In this paper, we evaluated the role of surgical margins, radiotherapy, and chemotherapy in myoepithelial carcinoma of soft tissue and bone (MC-SB) treated at our Institute.

METHODS

Medical records of 33 patients presenting with MC-SB between 1998 and 2015 at our institution were retrospectively analysed, and diagnosis and treatment were studied.

RESULTS

The median follow-up was 58.5 months. Twenty patients had tumours originating in soft tissues and 13 in bone. Eight patients (24.2%) had metastases at diagnosis, the remaining 25 had localised disease. Thirty-two underwent resection of the primary lesion. In 29 surgical margins were evaluated: wide in 28 with 10/28 who recurred (35.7%) and marginal resection in 1 who also recurred. Six patients received adjuvant radiotherapy. Metastases developed in 15/25 patients (60%) with localised disease at onset. Chemotherapy was administered in patients with metastatic advanced disease. Cisplatin+doxorubicin was administered in six patients as first-line chemotherapy with an objective response in 5/6 patients with a median 4-month duration. Five-year overall survival rate was 62.6% in patients with localised tumours and 12.5% in those metastatic at diagnosis.

CONCLUSIONS

MC-SB showed a high incidence of local recurrences and metastases. Despite different chemotherapy regimens, the outcome remains poor in patients with metastatic disease. Due to the absence of a standard protocol, we encourage treatment by multidisciplinary teams in referral centres with renowned expertise.

An intraosseous myoepithelial carcinoma with a EWSR1::PBX3 fusion

Herein we report a case of an intraosseous myoepithelial carcinoma harboring a EWSR1::PBX3 fusion gene. The patient was a 64-year-old male found to have a 7 cm destructive lesion in the distal ulna with an extraosseous soft tissue component. Microscopic examination of the resected tumor showed a spindle-cell lesion within a sclerotic stroma and intravascular tumor emboli. At higher power the tumor cells showed moderate nuclear atypia with a high mitotic count (20 per mm2 ). Immunohistochemistry revealed diffuse EMA positivity and focal pancytokeratin (AE1/AE3) and S100 expression, consistent with myoepithelial differentiation. NGS using the Oncomine Childhood Cancer Assay (Thermo Fisher Scientific, Inc.) revealed a EWSR1-PBX3 fusion and ABL amplification. The patient subsequently developed local recurrence as well as distant lymph node, lung and vertebral metastases; he is currently awaiting systemic treatment in the context of a clinical trial. In this report, we present a rare case of a skeletal myoepithelial tumor harboring a EWSR1::PBX3 fusion with demonstrated histological and clinical features of malignancy.

Myoepithelioma, myoepithelioma-like, and chondroid soft-tissue tumors arising at acral sites: a review

Myoepithelial neoplasms comprise a histologically and immunophenotypically diverse spectrum of entities. The following review is a comprehensive summary of acral lesions demonstrating myoepithelial-like and chondroid histomorphology, as well as recently described mimics that are diagnostically challenging to distinguish. The salient clinicopathologic, immunophenotypic, and molecular features of each entity are described.

Cutaneous Syncytial Myoepithelioma with Positive CD34 Immunohistochemical Staining: An Unusual Tumor and a Challenging Diagnosis

Cutaneous syncytial myoepithelioma (CSM) is a rare type of cutaneous neoplasm that typically presents as a solitary and well-circumscribed nodule on the skin. It predominantly occurs on the upper and lower extremities of adult patients. Immunohistochemically, CSM is characterized by the co-expression of smooth muscle and epithelial markers. Fluorescence in situ hybridization (FISH) targeting the EWSR1 gene rearrangement is an important diagnostic tool for CSM. In our case report, we found the focal positivity for CD34, which has never been previously observed; this was mostly confined to a central area of the neoplasm.

Practical Management of Adult Ultra-Rare Primary Retroperitoneal Soft Tissue Sarcoma: A Focus on Perivascular Epithelioid Tumours and Extraosseous Ewing Sarcoma

With the exception of well-differentiated liposarcoma, dedifferentiated liposarcoma, leiomyosarcoma, solitary fibrous tumour, malignant peripheral nerve sheath tumour, and undifferentiated pleomorphic sarcoma, the majority of the ≈70 histologic subtypes of retroperitoneal sarcoma are defined as 'ultra-rare' sarcomas, with an incidence of ≤1-5/1,000,000 persons/year. For most of these ultra-rare RPS subtypes, diagnosis and treatment follows international guidelines for the management of more common RPS histologies, with en bloc surgical resection as the mainstay of curative treatment, and enrolment in clinical trials where possible. Because the treatment of RPS is heavily driven by histology, the surgeon must be familiar with specific issues related to the diagnosis and management of ultra-rare sarcoma subtypes. Expert radiological and surgeon reviews are required to differentiate similarly presenting tumours where surgery can be avoided (e.g., angiomyolipoma), or where upfront systemic therapy is indicated (e.g., extraosseous Ewing's sarcoma). Thus, the management of all retroperitoneal sarcomas should occur at a sarcoma referral centre, with a multidisciplinary team of experts dedicated to the surgical and medical management of these rare tumours. In this focused review, we highlight how diagnosis and management of the ultra-rare primary RPS histologies of malignant perivascular epithelioid cell tumour (PEComa), extraosseous Ewing sarcoma (EES), extraosseous osteosarcoma (EOS), and rhabdomyosarcoma (RMS) critically diverge from the management of more common RPS subtypes.

Superficial mesenchymal tumours expressing epithelial markers on immunohistochemistry: Diagnostic clues and pitfalls

The diagnosis of mesenchymal neoplasms arising in the superficial soft tissue can be challenging as some entities are rare and show overlapping features. Moreover, the spectrum of mesenchymal tumours has expanded recently to include potential new entities, some of which have been described after the 5th edition of the World Health Organisation (WHO) classification of soft tissue and bone tumours published in 2020. In the skin and superficial soft tissue, tumours of epidermal, melanocytic and appendageal origin are more commonly encountered than mesenchymal neoplasms. However, specific entities from the latter category can occasionally express epithelial markers on immunohistochemistry, some of them in a strong and diffuse manner. It is therefore crucial to be aware of diagnostic pitfalls when encountering cytokeratin positivity in superficial soft tissue neoplasms. This article provides an overview on the differential diagnosis of these mesenchymal tumours that can sporadically occur also in the skin, including myoepithelial neoplasms, epithelioid sarcoma, keratin positive giant cell tumour of soft tissue / xanthogranulomatous epithelial tumour, superficial CD34-positive fibroblastic tumour / PRDM10-rearranged soft tissue tumour, and perineurioma.

Subcutaneous Myoepithelioma in the Extremity: A Potential Pitfall in the Differential Diagnosis of Subcutaneous Tumors

We present a rare case of myoepithelioma in the subcutaneous layer of the shoulder with ultrasonography (US) and magnetic resonance imaging (MRI). US showed a lobulated hyperechoic mass, leading to an impression of lipoma. MRI showed the mass with low signal intensity on T1-weighted images (T1WI), high signal intensity on fat-suppressed T2-weighted images (T2WI), intermediate signal intensity on T2WI, and intense enhancement with adjacent fascial thickening. Imaging findings of soft tissue myoepithelioma have not been established. We report its US and MRI features mimicking features from a lipomatous tumor to infiltrative malignancy. Although soft tissue myoepithelioma has nonspecific image findings to confirm its diagnosis, some findings may help to make the differential diagnosis. Preoperative pathologic confirmation is recommended in a soft tissue neoplasm.

Keratin-positive fibrotic extraskeletal myxoid chondrosarcoma: a close mimic of myoepithelial tumour

AIMS

Extraskeletal myxoid chondrosarcoma (EMC) is a rare form of adult sarcoma with distinct histology and NR4A3 gene fusion. Immunohistochemically, EMCs are variably positive for S100 protein and neuroendocrine markers. Unlike histologically similar soft-tissue myoepithelial tumours, keratin expression is rare. Prompted by two recent EMC cases with diffuse keratin expression, we investigated the expression of epithelial markers in a molecularly confirmed cohort of EMC and identified two additional similar cases.

METHODS AND RESULTS

Four keratin-positive EMCs occurred in one man and three women aged 46-59 years. All tumours displayed nonclassic histology with prominent stromal fibrosis, and keratin AE1/AE3 was expressed either diffusely (N = 2) or focally (N = 2). In one tumour, keratin expression was limited to the sclerotic area. All tumours coexpressed epithelial membrane antigen and two additionally expressed S100 protein or glial fibrillary acidic protein. All tumours harboured NR4A3 fusions, including TAF15::NR4A3 (N = 1) and EWSR1::NR4A3 (N = 3). Two cases were initially considered as most consistent with myoepithelial tumours based on widespread stromal fibrosis and keratin expression. DNA methylation analysis classified two tumours tested as EMCs.

CONCLUSIONS

We identified a small subset of EMCs characterised by keratin expression and prominent stromal fibrosis. This histological pattern must be recognised in the differential diagnosis of myoepithelial tumours because misclassification may lead to the erroneous prediction of tumour behaviour and may alter patient management. NR4A3 genetic analysis should be considered even in the face of keratin expression and prominent stromal fibrosis.

Uncommon metastases to the brain: Frontal lobe myoepithelial carcinoma

Background

Myoepithelial tumors have been widely described as a rare form of salivary gland neoplasm, although currently soft-tissue phenotypes have also been identified. These are tumors composed entirely of myoepithelial cells that exhibit a dual epithelial and smooth muscle phenotype. The occurrence of myoepithelial tumors within the central nervous system is also extremely rare, with only a few cases reported. Treatment options include surgical resection, chemotherapy, radiotherapy, or a combination of these approaches.

Case Description

The authors present a case of soft-tissue myoepithelial carcinoma with an unusual brain metastasis, rarely described in the literature. The purpose of this article is to present an update on the diagnosis and treatment of this pathology when affecting the central nervous system, through the review of the current evidence.

Conclusion

However, despite complete surgical resection, there is about a significative high rate of local recurrence and metastasis. Careful patient follow-up and staging is essential for better characterization and understanding of this tumor's behavior.

Myoepithelioma-like hyalinizing epithelioid tumor of the foot with OGT-FOX03 fusion gene: Imaging findings, surgical implications, and pathological correlates

Myoepithelioma-like hyalinizing epithelioid tumors are rare neoplasms that share morphological characteristics of myoepitheliomas but lack traditional immunophenotypic findings. Though little is known about these tumors at present, a handful of recent studies have confirmed that they harbor a novel fusion gene known as "OGT-FOXO." Though closely resembling myoeptheliomas, Myoepithelioma-like hyalinizing epithelioid tumors are considered a distinct tumor entity, and few studies have explored their clinical characteristics or their potential for malignancy. Furthermore, literature describing imaging findings of these tumors is virtually non-existent. Understanding the radiological and pathological differences between Myoepithelioma-like hyalinizing epithelioid tumors and myoepitheliomas is helpful in developing a comprehensive differential for soft tissue neoplasms of the foot. We describe a case of MHET of the foot and correlate MRI findings with pathology in addition to describing surgical technique and implications to care.

Primary myoepithelial carcinoma of the Vulva: Case of a rare tumor with malignant potential and review of literature

•Primary myoepithelial carcinoma is rare with a handful of cases reported from the vulva.•There is no standard of treatment for primary myoepithelial carcinoma.•Current recommendations suggest excision with wide margins to be the best therapy.•Chemotherapy and immunotherapy should be considered in combination with excision.

Abdominal myoepithelial carcinoma: A rare abdominal wall entity of an uncommon tumor

Introduction and importance

Case presentation

Clinical discussion

Conclusion

•

Extra-salivary myoepithelial carcinoma is an extremely rare entity, may present as an abdominal mass.

•

In contrast to their salivary-gland counterparts, most of them are malignant to begin with.

•

Limited data is available for their management, hence such patients should be enrolled in clinical trials whenever available.

Subungal Mixed Tumor Mimicking Glomus Tumor: A Case Report and Literature Review

Mixed tumors are well-circumscribed lesions exhibiting epithelial and/or myoepithelial cells and they usually occur in the skin and salivary glands. Soft tissue mixed tumors are extremely rare. Therefore, radiographic findings of soft tissue mixed tumors have very rarely been described in the radiologic literature. Here, we report a rare case of subungual mixed tumor in a 65-year-old female who presented with left 2nd finger pain, describe the radiographic findings, and discuss the differential diagnosis of the tumor.

Epithelial–myoepithelial carcinoma of the nasopharynx: A case report and review of the literature

Background

Epithelial–myoepithelial carcinoma (EMCa) is a rare low-grade malignant tumor that most commonly occurs in the salivary glands, with approximately 320 cases having been reported worldwide. Here, we report the third case of EMCa occurring in the nasopharynx. Rare cases in the breast, pituitary gland, lacrimal gland, nose, paranasal sinus, nasal cavity, trachea and bronchus, lung, and even the pleura mediastinalis have also been reported. Histopathology and immunohistochemistry are useful for confirming the diagnosis of EMCa, which is characterized by biphasic tubular structures composed of inner ductal and outer clear myoepithelial cells and stains for different markers in each layer. However, because of the rarity of EMCa, the clinicopathological characteristics and treatment of these patients remain unclear.

Case presentation

We report a rare case of EMCa of the nasopharynx. A 51-year-old man presented with a 5-month history of pain while swallowing and aggravation accompanied by right ear tinnitus lasting for 1 month. Nasopharyngoscopy and magnetic resonance imaging (MRI) of the nasopharynx and neck revealed a 5.6 cm × 3.4 cm × 3.1 cm mass in the nasopharyngeal space, invasion of the right cavernous sinus, and lymph node enlargement in the right retropharyngeal space. On 17 April 2019, based on the histopathological and immunohistochemical features, a final diagnosis of EMCa of the right nasopharynx was made. The patient underwent concurrent chemoradiotherapy (CCRT), and his symptoms were relieved after treatment. On 10 January 2022, nasopharynx MRI and biopsy revealed local recurrence, but chest and abdominal computed tomography (CT) showed no obvious signs of metastasis. The local recurrence-free survival (LRFS) period was 33 months.

Conclusion

To the best of our knowledge, this is the third reported case of EMCa in the nasopharynx and the only case of EMCa in the nasopharynx treated with CCRT, and a partial response was achieved. Therefore, to improve the quality of life and prognosis of patients with unresectable tumors, we believe that CCRT is a suitable option. Further clinical observations are required to elucidate the pathophysiology and prognosis of EMCa.

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.

Cutaneous Myoepithelial Neoplasms on Acral Sites Show Distinctive and Reproducible Histopathologic and Immunohistochemical Features

Cutaneous myoepithelial neoplasms are a heterogenous group of neoplasms with mixed tumors typically affecting the head and myoepitheliomas showing a predilection for the extremities. Their malignant counterparts, myoepithelial carcinoma, and malignant mixed tumor are exceptionally rare in the skin, and the morphologic criteria for malignancy are only poorly defined. The aim of the present study was to characterize the clinicopathologic features of myoepithelial neoplasms presenting on acral skin. The clinical and histopathologic features of 11 tumors were recorded, and follow-up was obtained. Immunohistochemistry was performed for S100, SOX10, glial fibrillary acidic protein, keratins, epithelial membrane antigen, p63, p40, smooth muscle actin, desmin, and PLAG1. The tumors mainly affected the feet of adults (range: 26 to 78 y; median: 47 y) with a predilection for the great toe and a male predominance of 1.8:1. Most tumors (91%) displayed a lobular architecture composed of solid and nested growth of epithelioid cells with plasmacytoid features in a myxoid or angiomatous stroma. Scattered cytologic atypia and rare duct differentiation were frequently noted. Three tumors with confluent cytologic atypia, infiltrative growth, and lymphovascular invasion were classified as malignant. By immunohistochemistry, the tumors were positive for S100, SOX10, keratins AE1/AE3, CK5/6 and CK7, and PLAG1. Local recurrence and bilateral pulmonary metastasis were observed in a patient presenting with a histopathologically benign-appearing tumor. Two patients with malignant tumors experienced local recurrences, and 1 developed metastasis to soft tissue, lung, and mediastinal lymph nodes. All patients are currently alive, all but 1 with no evidence of disease after a median follow-up interval of 96 months (range: 2 to 360 mo). In conclusion, acral myoepithelial neoplasms show distinctive and reproducible histopathologic and immunohistochemical features. They are best regarded as a distinctive subset of mixed tumors with features reminiscent of their salivary gland counterparts. While most tumors pursue a benign disease course, histopathologic features appear to be a poor indicator of prognosis.

Esophageal myoepithelial carcinoma: Four case reports

BACKGROUND

Myoepithelial carcinoma (MC) is a rare malignant neoplasm that mainly occurs in the salivary gland. MC can be confused with many other tumors when arising outside the salivary glands because it presents with a wide spectrum of cytomorphological and immunohistochemical features. To the best of our knowledge, esophageal MC has not been previously reported. The purpose of this study was to describe the imaging and clinicopathological features of esophageal MC to improve the understanding of the disease.

CASE SUMMARY

Three men and one woman diagnosed with esophageal MC were enrolled in this study. The primary clinical symptom was dysphagia. The mass was mainly located in the middle esophagus. Laboratory tests revealed that two patients who underwent tumor abnormal protein were positive. Radical resection was performed for all patients with no adjuvant therapy. Hematoxylin-eosin staining showed infiltrative growth of epithelial cells with hyperchromatic and pleomorphic nuclei toward the periphery. Immunohistochemistry showed that all patients were positive for P63, and most patients were positive for SOX-10, AE1/AE3, P40, and calponin. The Ki-67 values were all higher than 60%. Patient one died one month after discharge from an unknown cause. Patient two lost to follow-up. At patient three’s four-month review, enhanced computed tomography (CT) showed anastomosis recurrence and bilateral lung metastases. He abandoned treatment and lost to follow-up. Patient four attended review appointments regularly and remained in a good general condition.

CONCLUSION

Here, we present the first report of esophageal MC and review the relevant literature. Esophageal MC is more likely to occur in the middle esophagus in older patients with male dominance. A fungating type observed on CT scanning may help narrow down the differential diagnosis. Cystic change or necrosis may occur in larger lesions. The final diagnosis should be made according to the pathological examination. The treatment for MC is surgical resection, and the efficacy of chemotherapy needs to be determined with future studies.

Esophageal myoepithelial carcinoma: Four case reports

BACKGROUND

Myoepithelial carcinoma (MC) is a rare malignant neoplasm that mainly occurs in the salivary gland. MC can be confused with many other tumors when arising outside the salivary glands because it presents with a wide spectrum of cytomorphological and immunohistochemical features. To the best of our knowledge, esophageal MC has not been previously reported. The purpose of this study was to describe the imaging and clinicopathological features of esophageal MC to improve the understanding of the disease.

CASE SUMMARY

Three men and one woman diagnosed with esophageal MC were enrolled in this study. The primary clinical symptom was dysphagia. The mass was mainly located in the middle esophagus. Laboratory tests revealed that two patients who underwent tumor abnormal protein were positive. Radical resection was performed for all patients with no adjuvant therapy. Hematoxylin-eosin staining showed infiltrative growth of epithelial cells with hyperchromatic and pleomorphic nuclei toward the periphery. Immunohistochemistry showed that all patients were positive for P63, and most patients were positive for SOX-10, AE1/AE3, P40, and calponin. The Ki-67 values were all higher than 60%. Patient one died one month after discharge from an unknown cause. Patient two lost to follow-up. At patient three’s four-month review, enhanced computed tomography (CT) showed anastomosis recurrence and bilateral lung metastases. He abandoned treatment and lost to follow-up. Patient four attended review appointments regularly and remained in a good general condition.

CONCLUSION

Here, we present the first report of esophageal MC and review the relevant literature. Esophageal MC is more likely to occur in the middle esophagus in older patients with male dominance. A fungating type observed on CT scanning may help narrow down the differential diagnosis. Cystic change or necrosis may occur in larger lesions. The final diagnosis should be made according to the pathological examination. The treatment for MC is surgical resection, and the efficacy of chemotherapy needs to be determined with future studies.

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.

Myoepithelial carcinoma of soft tissue is a diagnostic challenge on fine-needle aspiration: Case report and review of literature

Myoepithelial carcinoma (MEC) of soft tissue, also known as malignant myoepithelial tumor, is an uncommon malignancy. Cytologic diagnosis of this entity is challenging due to its rarity and heterogeneous morphology. We report a case of MEC in a 22-year-old man, who presented with a 6.5 cm soft tissue mass on his right distal forearm that has been enlarging over the past 3 months. Ultrasound-guided fine-needle aspiration (FNA) revealed abundant isolated neoplastic cells ranging from spindled cells to epithelioid and plasmacytoid morphology in a myxoid background. These cells showed moderate cytologic atypia characterized by high-nuclear/cytoplasmic ratio, irregular nuclear contours, and prominent nucleoli. The cytoplasm varied from dense to vacuolated and occasionally rhabdoid with intracytoplasmic inclusions. Scattered bi- and multinucleated cells were identified. A diagnosis of high-grade malignancy was made with the differential diagnosis including rhabdomyosarcoma and melanoma. A subsequent core biopsy of the tumor showed immunoreactivity for pan-cytokeratins, calponin, p63, and smooth muscle actin. INI-1 was lost. SOX-10 and Melan-A were negative. Molecular studies showed loss of SMARCB1 (INI-1) and CDKN2A. Gene fusion studies did not detect any fusion. A diagnosis of soft tissue MEC was made which is a challenge on FNA due to several cytologic mimickers including rhabdomyosarcoma, epithelioid sarcoma, extrarenal rhabdoid tumor, extra-axial chordoma and melanoma. Recognition of the biphasic cell population in a myxoid background and a battery of immunohistochemical stains are crucial for accurate diagnosis.

[Fusion-related round and spindle cell sarcomas of the bone (beyond Ewing)]

Round cell sarcomas represent a diagnostic challenge for pathologists due to the poorly differentiated pattern of these high-grade tumors. Their diagnosis often requires large immunohistochemical panels and the use of molecular pathology. These tumors are largely dominated by Ewing sarcomas, but new families are now well characterized, including in decreasing frequency order in bone, BCOR-altered sarcomas, NFATc2-rearranged sarcomas, mesenchymal chondrosarcomas and more rarely CIC-rearranged sarcomas and myoepithelial tumors. This progress report presents microscopic, immunohistochemical and molecular features of these tumors previously named by the inappropriate term "Ewing-like" sarcomas, in order to enable any pathologist to perceive the morphological features of these sarcomas, to select the immunohistochemical panel that will lead to the diagnosis and to better guide the molecular approach needed to establish the final diagnosis.

Mutational and immunologic Landscape in malignant Salivary Gland Tumors harbor the potential for novel therapeutic strategies

Salivary gland carcinomas (SGC) are rare (3-6 % of all head and neck cancers) and show biological heterogeneity depending on the respective histological subtype. While complete surgical resection is the standard treatment for localized disease, chemotherapy or radiation therapy are frequently insufficient for the treatment of unresectable or metastasized SGC. Therefore, new therapeutic approaches such as molecularly targeted therapy or the application of immune checkpoint inhibition enhance the treatment repertoire. Accordingly, comprehensive analyses of the genomic landscape and the tumor-microenvironment (TME) are of crucial importance in order to optimize and individualize SGC treatment. This manuscript combines the current scientific knowledge of the composition of the mutational landscape and the TME in SGCs harboring the potential for novel (immune-) targeted therapeutic strategies.

A case of retroperitoneal tumor displaying epithelial differentiation, prominent myxoid stroma and loss of INI1/SMARCB1

The clinicopathological spectrum of INI1 deficient tumors is expanding. Epithelioid sarcoma (ES) is a rare sarcoma of uncertain differentiation, more often occurring in the extremities and uncommonly in the deep soft tissues. Histopathologically, it manifests in the form of classical, proximal, or hybrid types, the latter two characterized by rhabdoid cytomorphology. Immunohistochemically, ESs display loss of INI1/SMARCB1 and genetically associated with high percentage of SMARCB1 deletions

We report an extremely uncommon case of a retroperitoneal tumor in a 42-year-old male, who presented with abdominal discomfort. Radiologic imaging disclosed a 12 cm-sized retroperitoneal mass without involvement of any organ parenchyma. The patient underwent tumor excision with left-sided nephrectomy at another hospital. A review of the paraffin-embedded tissue sections revealed a multinodular tumor, composed of dyscohesive epithelioid tumor cells and focally arranged in cords, containing moderate to abundant, eosinophilic cytoplasm, vesicular nuclei, containing prominent nucleoli, including cells with rhabdoid cytomorphology, in a conspicuous myxoid stroma. A focal tumor area resembled proximal-type of ES. Immunohistochemically, tumor cells displayed positivity for pan cytokeratin (AE1/AE3), epithelial membrane antigen (EMA), vimentin and focally for CA125, while these were negative for CD34, S100 protein, CKIT, DOG1, and INI1/SMARCB1.

To the best of our knowledge, this constitutes the first case of a malignant tumor with epithelioid morphology, displaying myxoid matrix and loss of INI1/SMARCB1, resembling a myxoid variant of an epithelioid sarcoma and myoepithelioma-like tumor of the vulvar tumor, occurring in the retroperitoneum. A review of similar cases, differential diagnosis and treatment-associated implications are presented.

A unique case of adamantinoma-like Ewing sarcoma in the calcaneus, exhibiting prominent squamous differentiation and displaying EWSR1 gene rearrangement

Adamantinoma-like Ewing sarcoma is uncommonly reported in the skeletal sites, including small bones of the feet.A 15-year-old girl presented with pain and swelling in her left foot, leading to difficulty in walking for 8 months. Plain radiograph revealed an ill-defined, lytic-sclerotic lesion without significant periosteal reaction in her left calcaneus. Magnetic resonance imaging (MRI) revealed an expansile lesion involving the anterior calcaneus, which was hypointense on T1 and heterogeneously hyperintense on T2-weighted sequences, infiltrating the adjacent bones and soft tissues. On imaging, the differential diagnoses considered were a giant cell tumor and other primary bone tumors.Histopathological examination revealed a tumor composed of small round cells, with interspersed keratin pearls. Immunohistochemically, the tumor cells were positive for CD99/MIC2, pan-cytokeratin (AE1/AE3), p40, p63, NKX2.2, and synaptophysin. Diagnosis of adamantinoma-like Ewing sarcoma was offered on the initial biopsy. Furthermore, the tumor cells revealed EWSR1 gene rearrangement by fluorescence in situ hybridization, confirming this diagnosis. The patient underwent neoadjuvant chemotherapy, had a poor response, and finally underwent below-knee amputation.This constitutes a rare case of adamantinoma-like Ewing sarcoma in the calcaneus. Ewing sarcoma may be considered as a differential diagnosis for intraosseous lytic-sclerotic lesions, even without significant periosteal reaction, at unusual sites, such as the bones of the foot. Awareness of this entity and application of ancillary techniques is recommended for its exact diagnosis and in differentiating this rare variant from its diagnostic mimics. This case also indicates a poor chemotherapy response in this unusual variant of Ewing sarcoma, occurring in the calcaneus.

Anti-androgen for myoepithelial tumor: a potent therapy yet a potential misleader

Myoepithelial tumor is a rare form of cancer, mainly arising from the salivary glands and extremities. Due to its rarity, no formal treatment guidelines exist. Here we report a case of a male patient diagnosed with metastatic myoepithelial tumor which was successfully treated with an androgen-receptor (AR) antagonist (bicalutamide), based on the results of molecular testing. Six years after the initiation of bicalutamide, patient was diagnosed with metastatic prostate cancer. To our knowledge, this is the first case described in literature that demonstrate the effectiveness of anti-androgens in treating myoepithelial tumor. Vigilance should be maintained when screening these patients for prostate cancer as their 'true' prostate specific antigen levels might be masked by the ongoing endocrine therapy.

Myoepithelioma-like tumour of the vulval region: A case report

Myoepithelioma-like tumours of the vulvar region (MELTVR) are a newly described group of spindle cell neoplasm. Morphologically, they consist of epithelioid to spindled cells in a myxoid to collagenous stroma and can resemble epithelioid sarcomas, myoepithelial carcinomas or extraskeletal myxoid chondrosarcomas. However, they have a distinct pattern of immunohistochemical staining characterised by positivity for EMA, ER, PR and negativity for cytokeratin, GFAP and S100. Nuclear staining for INI-1 is lost. In addition, they lack the characteristic gene arrangements of these other lesions. MELTVR can recur locally when incompletely excised, however, do not appear to metastasize. We report a case of a MELTVR in a 49-year-old woman arising in the right mons pubis.

Epithelial-Myoepithelial Carcinoma of the Minor Salivary Glands: Case Series with Comprehensive Review

Epithelial-myoepithelial carcinoma (EMC) is a rare salivary gland tumor that is histologically characterized by biphasic tubular structures composed of inner ductal and outer clear myoepithelial cells, which is especially uncommon in the minor salivary glands (MSG). Because of its histologic variety, complexity, and heterogeneity, it is sometimes challenging to make the accurate diagnosis. Here, we report a literature review of EMC of the MSGs with our experience of two cases. Incisional biopsy was suggestive of pleomorphic adenoma in Case 1 and pleomorphic adenoma or a low-grade salivary gland carcinoma in Case 2. Both cases were performed intraoral tumor resection, and they have good postoperative courses and are alive with no evidence of local recurrence or metastasis at 31 and 16 months, respectively. Considering that the anatomy, structure, and size of salivary glands are quite different from MSGs, it might be difficult to predict EMCs of the MSG similarly to EMCs of the major salivary glands. This comprehensive review also reports the features of EMC of the MSG cases and the trends of diagnosis and discusses treatment strategy.

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.

Coincidence of Intracranial Myoepithelioma and Adrenocortical Carcinoma in a Young Man

Myoepithelial tumors are rare neoplasms that develop from myoepithelial cells in glandular structures and soft tissues. Primary intracranial myoepithelial neoplasms are even rarer with around ten cases reported. On the other hand, adrenocortical carcinoma (ACC) is also uncommon with an annual incidence of 0.7–2 per million and carries a poor prognosis. It is known to have an association with certain familial cancer syndromes. Even in sporadic cases, a significant portion of them had other malignancies before and after diagnosis of ACC. We reported a 34-year-old gentleman who was diagnosed to have ACC without known familial cancer syndrome. After that, he was also found to have right occipital myoepithelioma that was confirmed by excisional biopsy. There was no known association between these two pathologies. This is the first report of coincidence of ACC and intracranial myoepithelioma.

Fine-needle aspiration cytopathology of soft tissue myoepithelioma: an analysis of seven cases

INTRODUCTION

Soft tissue myoepithelioma (STM), a rare mesenchymal neoplasm morphologically analogous to its more common salivary gland (SG) counterpart, is the subject of single case reports regarding its fine-needle aspiration (FNA) biopsy. To our knowledge, ours is the first case series of STM.

MATERIALS AND METHODS

A search was made of our pathology databases for cases diagnosed as STM. FNA biopsy smears and cell blocks were performed using standard techniques.

RESULTS

Seven cases were retrieved from 4 men and 3 women (M:F = 1.3:1; age range: 25-79 years, x = 54 years). All but 1 presented as a primary neoplasm. Six aspirates were from the extremities, and 1 from the abdominal wall. Mean tumor size was 5.7 cm. Cytologic diagnosis of STM or suspicious for STM was made in 3 cases (43%). Remaining FNA diagnoses were spindle cell neoplasm/lesion (2), spindle cell sarcoma (1), and extraskeletal myxoid chondrosarcoma (1). Three cases were composed primarily or solely of uniform spindle cells, 3 primarily of uniform epithelioid cells with plasmacytoid features, and 1 case a mixture of these 2 cell types. Myxoid/chondromyxoid stroma was relatively abundant except in the single hypocellular example. Immunohistochemical (IHC) testing performed in 71% was nonspecific, but positive with S-100 in 4 of 5, EMA in 3 of 3, calponin in 2 of 2, and keratin in 1 of 3 examples.

CONCLUSION

FNA biopsy smears of STM are remarkably similar cytomorphologically to their SG equivalent. However, STM can be misidentified principally as extraskeletal myxoid chondrosarcoma, thus requiring a relatively broad IHC panel for a specific diagnosis.

Primary extradural tumors of the spinal column: A comprehensive treatment guide for the spine surgeon based on the 5th Edition of the World Health Organization bone and soft-tissue tumor classification

BACKGROUND

In 2020, the World Health Organization (WHO) published the 5th version of the soft tissue and bone tumor classification. Based on this novel classification system, we reviewed the current knowledge on all tumor entities with spinal manifestations, their biologic behavior, and most importantly the appropriate treatment options as well as surgical approaches.

METHODS

All tumor entities were extracted from the WHO Soft-Tissue and Bone Tumor Classification (5th Edition). PubMed and Google Scholar were searched for the published cases of spinal tumor manifestations for each entity, and the following characteristics were extracted: Growth pattern, ability to metastasize, peak age, incidence, treatment, type of surgical resection indicated, recurrence rate, risk factors, 5-year survival rate, key molecular or genetic alterations, and possible associated tumor syndromes. Surgical treatment strategies as well as nonsurgical treatment recommendations are presented based on the biologic behavior of each lesion.

RESULTS

Out of 163 primary tumor entities of bone and soft tissue, 92 lesions have been reported along the spinal axis. Of these 92 entities, 54 have the potential to metastasize. The peak age ranges from conatal lesions to 72 years. For each tumor entity, we present recommended surgical treatment strategies based on the ability to locally destruct tissue, to grow, recur after resection, undergo malignant transformation as well as survival rates. In addition, potential systemic treatment recommendations for each tumor entity are outlined.

CONCLUSION

Based on the 5th Edition of the WHO bone and soft tumor classification, we identified 92 out of 163 tumor entities, which potentially can have spinal manifestations. Exact preoperative tissue diagnosis and interdisciplinary case discussions are crucial. Surgical resection is indicated in a significant subset of patients and has to be tailored to the specific biologic behavior of the targeted tumor entity based on the considerations outlined in detail in this article.

Superficial ALK-rearranged myxoid spindle cell neoplasm: a cutaneous soft tissue tumor with distinctive morphology and immunophenotypic profile

Gene rearrangements involving the anaplastic lymphoma kinase (ALK) receptor tyrosine kinase gene have been identified in various neoplasms, including inflammatory myofibroblastic tumor and epithelioid fibrous histiocytoma. We present an ALK-rearranged cutaneous soft tissue tumor with unique morphologic and immunophenotypic features that are not shared by other entities with ALK rearrangements. The six cases involved two females and four males, aged 18-84 (mean 51) years old. Three tumors were on the back and three on the lower extremities (thigh, knee, shin); ranging from 0.5 to 5.6 (mean 2.1) cm. Four were confined to the dermis; two involved the subcutis. All six cases were characterized by the presence of spindled to ovoid cells arranged in concentric whorls and cords against a myxoid to myxohyaline stroma and relatively cellular aggregates of plump ovoid to epithelioid cells. Four cases showed distinct hyalinized blood vessels. Both cases that involved the subcutis showed peripheral lipofibromatosis-like areas. Tumor-infiltrating lymphocytes were absent to moderate. Severe cytologic atypia or conspicuous mitotic activity was not identified. Immunohistochemically, all tumors diffusely expressed ALK (D5F3) and CD34. All but one tumor was diffusely positive for S100 protein. All tumors were negative for EMA, AE1/AE3, SMA, and SOX10. Next-generation sequencing revealed ALK fusions with FLNA (3 cases), MYH10 (2 cases), and HMBOX1 (1 case) as the partner genes. In all six cases, the breakpoints involved exon 20 of ALK, which preserves the receptor tyrosine kinase domains of ALK in the fusion product. Of the four cases with limited follow-up information (2-18 months), none recurred. In conclusion, we report an ALK-rearranged cutaneous soft tissue tumor characterized by the presence of myxoid spindle cell whorls and cords, and co-expression of ALK, CD34, and frequently S100 protein, we term "superficial ALK-rearranged myxoid spindle cell neoplasm".