Myoepithelial carcinoma treatment in children: a report from the TREP project

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.

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.

Adamantinoma-like Ewing Sarcoma (ALES) May Harbor FUS Rearrangements : A Potential Diagnostic Pitfall

Adamantinoma-like Ewing sarcoma (ALES) is a rare malignancy currently considered a variant of Ewing sarcoma with most known cases harboring EWSR1 rearrangements. Herein we present a series of 6 cases of EWSR1 -negative ALES. The tumors arose in the sinonasal tract (n=3), major salivary glands (submandibular gland=1; parotid=1), and anterior mediastinum (n=1) in patients ranging from 25 to 79 years of age. Most tumors were basaloid in appearance, growing in large nests separated by interlobular fibrosis without overt squamous pearls. However, 1 case closely resembled a well-differentiated neuroendocrine tumor with uniformly round nuclei, eosinophilic cytoplasm, and trabecular architecture. All cases were diffusely positive for pan-cytokeratin, p40 or p63, and CD99. A subset of cases showed diffuse reactivity for synaptophysin, including 1 sinonasal tumor which also demonstrated sustentacular S100 protein expression. Molecular testing showed FUS rearrangements in all cases. Gene partners included known ETS family members FEV (n=2) and FLI1 (n=1). Our results expand the molecular diagnostic considerations for ALES to include FUS rearrangements. We also show that ALES may harbor FUS :: FLI1 fusion, which has not been previously reported in the Ewing family of tumors. Furthermore, ALES may show unusual histologic and immunophenotypic features that can overlap with olfactory carcinoma including S100-positive sustentacular cells. ALES should be considered in the diagnostic differential of small round cell tumors and tumors with neuroendocrine differentiation with immunohistochemical workup to include p40 and CD99/NKX2.2.

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.

Head and neck carcinoma in children: A clinicopathological study of 42 cases

Background/purpose

Cancer is an important part of the global burden of childhood diseases. Head and neck carcinoma in children is rare and related research is limited. This study aimed to investigate the clinicopathological features of childhood head and neck carcinoma.

Materials and methods

Forty-two cases of childhood head and neck carcinoma treated in our institution were reviewed and analyzed.

Results

Median age overall was 11 years. Twenty-three patients (54.8%) were male and 19 (45.2%) were female. Parotid gland location was most common (54.8%). Mucoepidermoid carcinoma and squamous cell carcinoma were the most common histological types (57.1% and 11.9%, respectively). Two patients had a history of bone marrow transplantation and two had a history of odontogenic keratocyst. The recurrence rate after treatment was 8.6%.

Conclusion

Early diagnosis and treatment and close follow-up of childhood head and neck carcinoma are warranted to prevent recurrence and improve clinical outcome.

Treatment Refractory Soft Tissue Myoepithelial Carcinoma With an ARID1A Mutation

Soft tissue myoepithelial carcinoma is a rare tumor first reported in the salivary gland. There is considerable tumor heterogeneity between pathology findings, tumor aggressiveness, and response to treatment. Recent molecular testing has identified recurrent genetic changes with PLAG mutations in salivary gland primary tumors and loss of SMARCB1 and EWSR1/FUS gene changes in myoepithelial carcinoma. SMARCB1 is a component of the switch/sucrose nonfermentable (SWI/SNF) complex, an essential cellular regulator. ARID1A is another SWI/SNF complex subunit and is a potent oncogenic driver in other tumor types. In this case, we describe the case of an adolescent/young adult patient with treatment refractory soft tissue myoepithelial carcinoma and a previously unreported ARID1A mutation.

Myoepithelial Carcinoma of Soft Tissue With an EWSR1-KLF15 Gene Fusion in an Infant

Overall, neonatal cancer is uncommon. Because of its rarity and heterogeneity, diagnosis can be challenging. We report a unique case of a myoepithelial carcinoma in a 7 week old girl. Molecular diagnostic workup revealed a EWSR1-KLF15 gene fusion which was previously described in only six cases of myoepithelial tumors so far. All cases occurred in children and adolescents. To our knowledge, this is the first report of a congenital EWSR1-KLF15 fusion positive myoepithelial tumor in an infant.

Aggressive myoepithelial carcinoma with EWSR1-POU5F1 fusion highly responsive to Ewing sarcoma combination chemotherapy

This article describes a case of metastatic, bulky, high‐grade, rapidly progressive myoepithelial carcinoma with EWSR1‐POU5F1 fusion originating from the left kidney that demonstrated a dramatic, deep response within 2 cycles of treatment with a regimen used for patients with Ewing sarcoma and an ongoing sustained response of >10 months. To the author's knowledge, this is the first report of a rapid and deep response using a systemic therapy regimen in a patient with myoepithelial carcinoma with EWSR1‐POU5F1 fusion.

Myoepithelial Carcinoma of Urinary Bladder in a Pediatric Patient. A Case Report

Myoepithelial carcinoma is a rare pathological variant, usually expressed in salivary gland. This case report describes a case of pediatric myoepithelial carcinoma in the urinary bladder. A 4-year-old male patient was admitted to a specialized hospital in Lima, Peru for hematuria. A CT scan showed a tumor lesion in the bladder wall, and biopsy revealed myoepithelial carcinoma of urinary bladder. Six courses of chemotherapy + partial cystectomy + radiotherapy was completed. The treatment was defined based on the pathological variant and the tumor location. The patient is currently at 2 years of disease-free survival.

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.

A Rare Case of an Intracardiac Myoepithelial Carcinoma in an Infant

Myoepithelial carcinomas (MC) represent aggressive tumors that occur in a myriad of ages and anatomic locations. The rarity and histologic similarity with other tumors make them difficult to diagnosis. We report an extremely rare case of a right ventricular outflow tract mass identified to be an intracardiac MC in a 4-month-old male infant. Pathology revealed an EWS-KLF15 translocation. Treatment included gross total resection and intensive chemotherapy. Recurrent cardiac mass with brain metastasis was seen 16 months after primary diagnosis. We describe the rarity of intracardiac MC in pediatric patients and the challenges encountered in the multimodal management of this patient.

Rhabdomyosarcoma

Rhabdomyosarcoma (RMS) is the most common soft tissue sarcoma in children and represents a high-grade neoplasm of skeletal myoblast-like cells. Decades of clinical and basic research have gradually improved our understanding of the pathophysiology of RMS and helped to optimize clinical care. The two major subtypes of RMS, originally characterized on the basis of light microscopic features, are driven by fundamentally different molecular mechanisms and pose distinct clinical challenges. Curative therapy depends on control of the primary tumour, which can arise at many distinct anatomical sites, as well as controlling disseminated disease that is known or assumed to be present in every case. Sophisticated risk stratification for children with RMS incorporates various clinical, pathological and molecular features, and that information is used to guide the application of multifaceted therapy. Such therapy has historically included cytotoxic chemotherapy as well as surgery, ionizing radiation or both. This Primer describes our current understanding of RMS epidemiology, disease susceptibility factors, disease mechanisms and elements of clinical care, including diagnostics, risk-based care of newly diagnosed and relapsed disease and the prevention and management of late effects in survivors. We also outline potential opportunities to further translate new biological insights into improved clinical outcomes.

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.

Congenital Myoepithelial Carcinoma of Soft Tissue Associated With Cystic Myoepithelioma

Myoepithelial neoplasms of soft tissue represent a heterogeneous group of lesions, encompassing both benign entities as myoepithelioma (ME) and highly aggressive tumors as myoepithelial carcinoma (MEC). We describe a case of pediatric soft tissue MEC with peculiar features that may lead to misdiagnosis: congenital onset and presence of a benign component with predominant cystic structure. Few cases of congenital MEC have been reported, but the coexistence of MEC with ME is even more rare, accounting for less than 1% of myoepithelial tumors. Moreover, an extensive cystic appearance had never been described in either ME or MEC of soft tissue. Despite several predictors of poor prognosis, the patient has been showing a favorable clinical course since the administration of ICpE (ifosfamide, cisplatin, and etoposide) chemotherapy. This report provides valuable information in the differential diagnosis of cystic congenital tumors and supports a possible efficacy of adjuvant combined treatment for patients with localized disease after surgery.

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.

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.

Myoepithelial Carcinoma: The Role of Radiation Therapy. A Case Report and Analysis of Data From the Surveillance, Epidemiology, and End Results (SEER) Registry

PURPOSE/OBJECTIVE

The role of radiation therapy in the treatment of myoepithelial carcinoma (MC) is unknown. We present a case of a high-grade soft-tissue MC in a pediatric patient and retrospectively examine the effect of postoperative radiation on survival in patients with MC.

MATERIALS AND METHODS

Our patient was treated with 4 cycles of ifosfamide, cisplatin, and etoposide followed by 3 cycles of ifosfamide vincristine and etoposide. Radiation was delivered to a total dose of 5580 cGy in 180 cGy/fraction to the surgical bed with a 2 cm margin starting after the third cycle of chemotherapy. The Surveillance, Epidemiology, and End Results (SEER) registry database was queried for cases of surgically resected MC. Retrospective analysis was performed with the endpoint of overall survival (OS).

RESULTS

Two hundred thirty-four cases of MC were identified; for 62 of these cases, the grade of the tumor wasidentified. Of these 62 patients, 27 received postoperative radiation. OS was improved with adjuvant radiation therapy in patients with grade III or IV MC (P<0.01) as determined by the log-rank test.

CONCLUSIONS

This analysis of SEER data showed an OS benefit with adjuvant radiation therapy in the treatment of high-grade MC. Physicians should report all cases of MC to improve clinical decision making in the treatment of this rare disease.

Translational Research in Pediatrics IV: Solid Tissue Collection and Processing

Solid tissues are critical for child-health research. Specimens are commonly obtained at the time of biopsy/surgery or postmortem. Research tissues can also be obtained at the time of organ retrieval for donation or from tissue that would otherwise have been discarded. Navigating the ethics of solid tissue collection from children is challenging, and optimal handling practices are imperative to maximize tissue quality. Fresh biopsy/surgical specimens can be affected by a variety of factors, including age, gender, BMI, relative humidity, freeze/thaw steps, and tissue fixation solutions. Postmortem tissues are also vulnerable to agonal factors, body storage temperature, and postmortem intervals. Nonoptimal tissue handling practices result in nucleotide degradation, decreased protein stability, artificial posttranslational protein modifications, and altered lipid concentrations. Tissue pH and tryptophan levels are 2 methods to judge the quality of solid tissue collected for research purposes; however, the RNA integrity number, together with analyses of housekeeping genes, is the new standard. A comprehensive clinical data set accompanying all tissue samples is imperative. In this review, we examined: the ethical standards relating to solid tissue procurement from children; potential sources of solid tissues; optimal practices for solid tissue processing, handling, and storage; and reliable markers of solid tissue quality.

Adamantinoma-like Ewing family tumors of the head and neck: a pitfall in the differential diagnosis of basaloid and myoepithelial carcinomas

Ewing sarcoma family tumors (EFTs) of the head and neck are rare and may be difficult to diagnose, as they display significant histologic overlap with other more common undifferentiated small blue round cell malignancies. Occasionally, EFTs may exhibit overt epithelial differentiation in the form of diffuse cytokeratin immunoexpression or squamous pearls, resembling the so-called adamantinoma-like EFTs and being challenging to distinguish from bona fide carcinomas. Furthermore, the presence of EWSR1 gene rearrangement correlated with strong keratin expression may suggest a myoepithelial carcinoma. Herein, we analyze a series of 7 adamantinoma-like EFTs of the head and neck, most of them being initially misdiagnosed as carcinomas because of their anatomic location and strong cytokeratin immunoexpression, and subsequently reclassified as EFT by molecular techniques. The tumors arose in the sinonasal tract (n=2), parotid gland (n=2), thyroid gland (n=2), and orbit (n=1), in patients ranging in age from 7 to 56 years (mean, 31 y). Microscopically, they departed from the typical EFT morphology by growing as nests with peripheral nuclear palisading and prominent interlobular fibrosis, imparting a distinctly basaloid appearance. Moreover, 2 cases exhibited overt keratinization in the form of squamous pearls, and 1 sinonasal tumor demonstrated areas of intraepithelial growth. All cases were positive for CD99, pancytokeratin, and p40. A subset of cases showed synaptophysin, S100 protein, and/or p16 reactivity, further confounding the diagnosis. Fluorescence in situ hybridization assays showed EWSR1 and FLI1 rearrangements in all cases. Our results reinforce that a subset of head and neck EFTs may show strong cytokeratin expression or focal keratinization, and are therefore histologically indistinguishable from more common true epithelial neoplasms. Thus, CD99 should be included in the immunopanel of a round cell malignancy regardless of strong cytokeratin expression or anatomic location, and a strong and diffuse CD99 positivity should prompt molecular testing for the presence of EWSR1 gene rearrangements.

Salivary gland myoepithelial carcinoma

Salivary gland myoepithelial carcinoma (MC) or malignant myoepithelioma is a rare entity. MC usually presents as a slow-growing painless mass arising in the parotid gland, but may involve other salivary glands. This tumour may be particularly locally aggressive, but its clinical and biological features are not yet fully understood. MC may arise from pre-existing benign lesions, such as pleomorphic adenomas or benign myoepitheliomas, or may arise de novo. It usually affects patients over 50 years old, with no gender preference. Because it is often asymptomatic, the presentation and diagnosis can be delayed by months, even years. The current WHO classification considers MC to be an intermediate- to high-grade malignancy. Other published data suggest it is likely to be a high-grade neoplasm, consistent with its aggressive behaviour. Its epidemiology, histopathological features, immunohistochemical profile, clinical behaviour and optimal management are not well understood. Following review of the current literature we aim to address these.