Perivascular epithelioid cell tumour: dynamic CT, MRI and clinicopathological characteristics--analysis of 32 cases and review of the literature

A case report and literature review: leiomyosarcoma or perivascular epithelioid cell neoplasm?

The distinction between a uterine leiomyosarcoma (uLMS) and a perivascular epithelioid cell neoplasm (PEComa) can be quite challenging. Here we report a 39-year-old woman who underwent a hysteroscopic myomectomy. An intraoperative frozen section pathological examination revealed that the mass was likely to be a mesenchymal malignancy. After consultation with her family, a total hysterectomy and bilateral salpingo-oophorectomy were performed. Postoperative pathological examinations suggested leiomyosarcoma but a malignant PEComa cannot be completely excluded. Combining the present case and prior studies, we summarized the clinical manifestations, pathological features, genomic characterization, and treatment of LMS and PEComa.

Clear cell myomelanocytic tumor of ligamentum teres

Clear cell myomelanocytic tumor (CCMMT) of the falciform ligament/ligamentum teres is a rare hepatic tumor, a variant of the perivascular epithelioid cell tumor (PEComa) family. CCMMT is the rarest variant of hepatic PEComas. Only a few cases of CCMMT have been reported in the English literature. Because of its rarity, less is known about its biological behavior. We present a case of a 31-year-old female who complained of abdominal pain, bilious vomiting, and abdominal fullness over two months. The radiological impression was of focal nodular hyperplasia. The histological examination of the resection specimen revealed a well-circumscribed tumor arranged in fascicles, sheets, and a whorling pattern. The tumor cells were spindle to epithelioid shaped with abundant clear to pale eosinophilic cytoplasm. The tumor cells expressed both myoid (smooth muscle actin) and melanocytic (MelanA and HMB45) markers, while they were negative for hepatocytic and vascular markers. Thus, based on histology and immunohistochemistry, a diagnosis of CCMMT was made. This case presents the diagnostic challenges of CCMMT and discusses the differential diagnosis with a literature review.

Comprehensive Insights Into Renal Perivascular Epithelioid Cell Neoplasms: From Molecular Mechanisms to Clinical Practice

Perivascular epithelioid cell neoplasms (PEComas) are a rare category of mesenchymal tissue tumors, manifesting across various tissues and organs such as the kidneys, liver, lungs, pancreas, uterus, ovaries, and gastrointestinal tract. They predominantly affect females more than males. PEComas characteristically express both melanocytic and smooth muscle markers, making immunohistochemistry vital for their diagnosis. Renal angiomyolipoma (AML) represents a common variant of PEComas, typically marked by favorable prognoses. Nonetheless, only a small fraction of subtypes, especially epithelioid AML, possess the capacity to be malignant. Renal PEComas usually appear as asymptomatic masses accompanied by vague imaging characteristics. The main methods for diagnosis are histopathological analysis and the application of immunohistochemical stains. Presently, a uniform treatment plan for renal PEComas is absent. Strategies for management include active surveillance, selective arterial embolization, surgical procedures, and drug-based treatments. The focus of this review is on renal PEComas, shedding light on their pathogenesis, pathological characteristics, clinical presentations, diagnosis, and treatment modalities, and incorporating a clinical case study.

Systematic analysis of perivascular epithelioid cell neoplasms in the female reproductive tract: a comprehensive review

Perivascular epithelioid cell neoplasms (PEComas) are rare mesenchymal lesions, with gynecological PEComas accounting for just over a quarter of cases. Limited reports exist on gynecological PEComa, primarily treated with surgery; adjuvant therapy is considered in high-risk cases. This systematic review aims to summarize the origin and clinical, pathological and molecular characteristics of uterine PEComa, focusing on treatment options for gynecological PEComa. A comprehensive PubMed review of gynecological PEComa reports was conducted. A detailed examination of the literature ensured a thorough understanding. Gynecological PEComa diagnosis relies on histology and immunology. Despite therapy controversies, surgery remains the mainstay. Adjuvant therapy efficacy in high-risk cases is uncertain. mTOR inhibitors are the first line; alternative treatments, including angiogenesis and aromatase inhibitors, should be considered.

Pancreatic PEComa, a not so uncommon neoplasm? Systematic review and therapeutic update

Pancreatic PEComas are extremely rare neoplasms with malignant potential, which mostly affect middle-aged women and are characterized by presenting melanocytic and myogenic markers in immunohistochemical analysis. There are no symptoms or pathognomonic imaging tests, so the diagnosis is established with the analysis of the surgical specimen or the FNA obtained with preoperative endoscopic ultrasound. The mean treatment consists on radical excision, adapting the intervention to the location of the tumor. To date, 34 cases have been described; however, more than 80% of them have been reported in the last decade, which suggests that it is a more frequent pathology than expected. A new case of pancreatic PEComa is reported and a systematic review of the literature is carried out according to the PRISMA guidelines with the aim of divulge this pathology, deepening its knowledge and updating its management.

Multimodal imaging study of hepatic perivascular epithelioid cell tumors: a case report

Hepatic perivascular epithelioid cell tumors (PEComas) are rare interstitial tumors that are often misdiagnosed as hepatocellular carcinomas due to their unique vascular enhancement patterns. Herein, we present a case of a 61-year-old man who was incidentally found to have a lesion in the left medial segment of the liver during a chest computed tomography (CT) examination performed 4 days prior to his presentation for chest discomfort. Imaging revealed solid components with density similar to that of normal liver tissue and areas of low-density adipose tissue within the lesion. The solid components exhibited increased uptake of fluorine-18 fluorodeoxyglucose on positron emission tomography/CT. Magnetic resonance imaging demonstrated areas with unevenly high signal intensity in both T1-weighted imaging (T1WI) in-phase and T2-weighted imaging (T2WI) sequences, while T2WI in the opposite phase displayed areas with unevenly low signal intensity, indicating the presence of fatty components. Contrast-enhanced T1WI displayed a "fast in and fast out" enhancement pattern. These distinct imaging features contribute to the diagnosis of hepatic PEComas and distinguish it from hepatocellular carcinoma.

Contrasting Outcomes in Two Cases of Uterine PEComa

Perivascular epithelioid cell tumours of the uterus are rare neoplasms with only few cases described in the literature. Ongoing contribution to the literature is important in order to understand the natural history for the diagnosis and management challenges for PEComa. We present two contrasting cases of PEComa who presented with postmenopausal bleeding, were diagnosed on endometrial biopsy and had surgical treatment. The first patient following treatment has been disease free for four years while on regular follow-ups. The second patient had aggressive disease developed early recurrence requiring chemotherapy and died in 17 months from diagnosis.

PEComa is a rare tumour with usually good outcomes, where surgery itself is adequate treatment. There is not much evidence available currently on the use of chemotherapy in rare cases, such as our second case, where PEComa presents aggressively. In this article, we elaborate two cases of contrasting outcomes with one presentation being aggressive requiring chemotherapy. We evaluated the current evidence on use of chemotherapy in rare cases.

A Case of Uterine Lymphangioleiomyomatosis Complicated by Tuberous Sclerosis Complex

Lymphangioleiomyomatosis (LAM) is one of the presentations of perivascular epithelioid cell neoplasm that is frequently complicated by tuberous sclerosis complex (TSC). Here, we report an uncommon case of uterine LAM treated with everolimus, which is a mechanistic target of rapamycin (mTOR) inhibitor. A 42-year-old female patient (gravida 0) with a history of TSC presented with abdominal pain. Pelvic magnetic resonance imaging showed multiple masses in the uterine myometrium, suggesting tumors that may contain internal hemorrhagic components. The lesions were suspected as the root cause of her symptoms. After everolimus was administered for a previously diagnosed renal angiolipoma, her uterine tumors temporarily decreased in size. Subsequently, laparoscopic hysterectomy and bilateral salpingectomy were performed since she could not tolerate everolimus for a long period due to the medication's side effects. Furthermore, the patient was diagnosed with LAM through histopathological examination after surgical resection. Therefore, it is advisable to suspect and investigate uterine LAM when a patient with a history of TSC presents with irregular genital bleeding or abdominal pain. Moreover, mTOR inhibitors may be a treatment option, in addition to surgery, in cases of uterine LAM exacerbation.

Renal and mediastinal perivascular epithelioid cell tumors (PEComas) in a young child with Tuberous Sclerosis; a rare case report

We describe a unique case of perivascular epithelioid cell tumors PEComas occurring as mediastinal and left renal soft tissue masses discovered incidentally in a five-year-old Tuberous Sclerosis patient upon presentation to the emergency department for upper respiratory illness. The radiographic features were non-specific. However, the similar CT characteristics of both lesions and background history raised the suspicion of a synchronous mesenchymal tumor, and histopathology confirmed the diagnosis. The rarity of these tumors in the pediatric population and lack of specific diagnostic criteria impose reporting the case and emphasize the need for further research on imaging features of such tumors.

Perivascular epithelioid cell tumour-mimicking retroperitoneal leiomyosarcoma

A young man in his 40s was evaluated in the emergency department for abdominal and right flank pain. A CT scan of the abdomen and pelvis showed a solid, well-circumscribed lesion measuring 7.1×8.1×5.4 cm, which was arising from the retroperitoneum and extending from the third portion of the duodenum towards the right kidney. A percutaneous core biopsy was obtained, demonstrating an atypical smooth muscle neoplasm suggestive of a low-grade leiomyosarcoma. The patient underwent surgery for an en-block resection of the mass and the final pathology confirmed a perivascular epithelioid cell neoplasm without significant pleomorphism, mitosis or necrosis. Our case adds to the small number of perivascular epithelioid cell tumour cases reported in the literature and we present it in order to increase our understanding of this tumour and to assist in its appropriate diagnosis and management.

Pediatric case of colonic perivascular epithelioid cell tumor complicated with intussusception and anal incarceration: A case report

BACKGROUND

Perivascular epithelioid cell tumor (PEComa) represents a group of rare mesenchymal tumors. PEComa can occur in many organs but is rare in the colorectum, especially in children. Furthermore, PEComa is a rare cause of intussusception, the telescoping of a segment of the gastrointestinal tract into an adjacent one. We describe a rare case of pediatric PEComa complicated with intussusception and anal incarceration, and conduct a review of the current literature.

CASE SUMMARY

A 12-year-old girl presented with abdominal pain and abdominal ultrasound suggested intussusception. Endoscopic direct-vision intussusception treatment and colonoscopy was performed. A spherical tumor was discovered in the transverse colon and removed by surgery. Postoperative pathologic analyses revealed that the tumor volume was 5.0 cm × 4.5 cm × 3.0 cm and the tumor tissue was located in the submucosa of the colon, arranged in an alveolar pattern. The cell morphology was regular, no neoplastic necrosis was observed, and nuclear fission was rare. The immunohistochemical staining results were as follows: Human melanoma black 45 (HMB 45) (+), cluster of differentiation 31 (CD31) (+), cytokeratin (-), melanoma-associated antigen recognized by T cells (-), smooth muscle actin (-), molleya (-), desmin (-), S-100 (-), CD117 (-), and Ki67 (positive rate in hot spot < 5%). Combined with the results of pathology and immunohistochemistry, we diagnosed the tumor as PEComa. Postoperative recovery was good at the 4 mo follow-up.

CONCLUSION

The diagnosis of PEComa mainly depends on pathology and immunohistochemistry. Radical resection is the preferred treatment method.

TFE3-associated perivascular epithelioid cell tumor with complete response to mTOR inhibitor therapy: report of first case and literature review

BACKGROUND

Perivascular epitheloid cell tumor (PEComas) are characterized by expression of both muscles, most often smooth muscle actin (in ~80% of cases) and melanocytic markers (mainly HMB-45 and Melan A). TFE 3-associated PEComas are new variant which are poorly defined due to their limited reports in literature. These tumors lack response to targeted mTOR inhibitor therapy due to lack of mutation in TSC gene. Hereby, we are reporting a case of TFE3 associated pelvic PEComa showing excellent response to Everolimus.

CASE PRESENTATION

A 45-year-old female presented with complaint of abdominal mass and bleeding per vaginum for 4 months. She had a history of total abdominal hysterectomy 3 years back in view of abnormal uterine bleeding and exploratory laprotomy 7 months back to remove some pelvic mass. Imaging suggested of ill-defined heterogenous mass of 9.3 x 9.2 x 16 cm involving the uterus, cervix, and upper 1/3 vagina. Multiple omental and peritoneal deposits were also seen, making probable diagnosis of carcinoma endometrium. USG guided biopsy showed cores of fibrous tissue with the presence of cells in sheets with granular eosinophillic cytoplasm; IHC showed positivity for TFE-3, H Caldesmon, GATA-3, and Melan A- and HMB-45; and Ki 67 index was 35%. The basis of above diagnosis of PEComa was made and she was started on Everolimus; repeat imaging after 3 months of therapy showed complete response.

CONCLUSION

We are reporting first case of malignant pelvic TFE 3 PEComa showing response to mTOR therapy. Identification of TFE 3 PEComa is important because they showed different biologic behavior then their conventional PEComa.

Pregnancy-Associated Perivascular Epithelioid Cell Tumor of the Tarsal Navicular: A Case Report

CASE

A 30-year-old pregnant woman with perivascular epithelioid cell tumor (PEComa) of the tarsal navicular underwent intralesional curettage with allograft at 30 weeks' gestation. She had an uncomplicated delivery at term and is ambulating without tumor recurrence at 1-year follow-up.

CONCLUSION

PEComas are rare tumors most commonly found in soft tissues but have been reported in bone and are occasionally associated with pregnancy. To the best of our knowledge, this is the first reported case of pregnancy-associated PEComa of bone.

Multifocal retroperitoneal and pelvic PEComas mimicking liposarcoma: A case report and review of literature

Perivascular epithelioid cell neoplasms (PEComa) constitute a rare, but increasingly recognized family of seemingly distinct mesenchymal tumors which can occur in any part of the body. Due to their rarity, radiological descriptions of PEComas in the current literature are few and non-specific, making diagnosis difficult, though some common imaging features have been reported. We present an unusual case of multifocal retroperitoneal and pelvic PEComas, mimicking liposarcoma, subsequently treated with open surgery.

Primary perivascular epithelioid cell tumor (PEComa) in bone: A review of the literature and a case arising in the humerus with multiple metastases

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First case PEComa primary arising in humerus was described.

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Histology is the basic to determine malignancy of PEComa.

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TFE3 gene investigation is the key of therapy selection.

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mTOR inhibitor is believed to be effective for patients without TFE3 rearrangement.

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More study is needed to understand the role of molecular test and imaging in PEComa.

Introduction

Perivascular epithelioid cell tumors (PEComas) are a family of mesenchymal tumors that rarely arise as a primary bone tumor.

Material and methods

We report a case of primary malignant bone PEComa. A literature review via PubMed, Embase and Web of Science databases with the keyword “PEComa” and “bone” was performed.

Results

We reported a 33-year-old female with primary malignant bone PEComa in right distal humerus. The patient received an inhibitor of the mammalian target of rapamycin (mTOR) protein based on negative molecular investigation result of transcription factor E3 (TFE3) rearrangement, and additional therapies including palliative radiotherapy, anti-angiogenics and immunotherapy when the disease progression was detected. The patient was alive with the disease twenty-three months postoperatively. A total of nineteen related literature cases were retrieved and reviewed. Taking current case into account, ten males and ten females with median age of 24 years (range, 3–93 years) were identified, who were most frequently affected in tibia. The median follow-up duration of 24 months (range, 3–96 months). One patient died due to this disease, and six patients showed metastases. Three patients experienced recurrence, and two of them experienced twice and three times, respectively.

Conclusion

To our knowledge, this is the first case of primary malignant bone PEComa arising in humerus. Clinicopathological and radiological correlation is mandatory to the correct diagnosis and to determine its malignancy. More studies are required to understand the role of molecular test and imaging in selecting suitable treatment and mechanisms of treatment resistance.

Abdominal perivascular epithelioid cell tumor (PEComa) without visible fat: a clinicopathologic and radiological analysis of 16 cases

OBJECTIVE

To retrospectively review the clinicopathological features and computed tomography (CT) and magnetic resonance imaging (MRI) findings of abdominal perivascular epithelioid cell tumor without visible fat (PEComa_wvf).

MATERIALS AND METHODS

Sixteen patients with surgically and pathologically confirmed perivascular epithelioid cell tumor without visible fat were enrolled. Their clinicopathological data and imaging findings were retrospectively reviewed. The CT and MRI features, including location, size, shape, margin, density, calcification, cystic necrosis and enhancement pattern, were analyzed.

RESULTS

There were 4 males and 12 females (median age, 46 years; range, 21-65 years) in this study. All 16 patients were diagnostic asymptomatic unenhanced CT or MRI and revealed a well-defined (n = 13), oval (n = 10), mass with heterogeneous (n = 6) or homogeneous density/signal intensity (n = 7), calcification and hemorrhage was no found in any cases. On enhanced CT/MRI, markedly enhancement patterns (n = 14) were observed. The "peripheral enhancement" sign was observed in 13 cases. One in 16 cases recurrence was discovered during the follow-up period.

CONCLUSIONS

Dynamic CT, MRI and pathology of PEComa_wvf had some characteristics of non-aggressive pattern of performance, and MRI would provide beneficial detection of microscopic fat. Enhanced imaging showed PEComa_wvf is characterized by a "peripheral enhancement" with a marked enhancement pattern. Knowing these characteristics could contribute to improving the understanding abdominal PEComa_wvf and related palliative care.

Robotic wedge resection of a rare gastric perivascular epithelioid cell tumor: A case report

BACKGROUND

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm that can arise in many different organs with a broad spectrum of biological behavior, from indolent to aggressive progression. Only ten cases of gastric PEComas have been reported in the English literature, which were treated with endoscopic, laparoscopic, or open resections. Due to its rarity, the optimal surgical management and prognosis of this tumor are still uncertain.

CASE SUMMARY

We present a case of robotic wedge resection of a 6.5 cm bleeding lesion of the gastric fundus located 3 cm below the esophago-gastric junction in a 55-year-old man. Biopsy revealed a malignant tumor with epithelioid cells focally positive for muscle markers desmin and smooth muscle actin. In addition, histology revealed that the tumor was positive for HMB-45, melan-A (MART-1), microphthalmia transcription factor and negative for pan-cytokeratin AE1/AE3, CD34, p40, DOG-1, CD117 (c-kit), S100, CD3, CD79a, caldesmon and myogenin. These markers suggested the possibility of a PEComa. The patient underwent a diagnostic laparoscopy via the da Vinci® Si™ system and robotic wedge resection. Final pathology confirmed a malignant gastric PEComa with negative margins. At his 11-mo follow-up visit, the patient remained disease-free.

CONCLUSION

Gastric PEComa can be treated with a robotic R0 resection with acceptable postoperative and short-term oncological outcomes.

Retroperitoneal perivascular epithelioid cell tumours: A case report and review of literature

BACKGROUND

The perivascular epithelioid cell tumour (PEComa) family of tumours mainly includes renal and hepatic angiomyolipomas, pulmonary lymphangioleiomyomatosis and clear cell “sugar” tumour of the lung. Several uncommon tumours with similar morphological and immunophenotypical characteristics arising at a variety of sites (abdominal cavity, digestive tract, retroperitoneum, skin, soft tissue and bones) are also included in the PEComa family and are referred to as PEComas not otherwise specified.

CASE SUMMARY

We present a 37-year-old female patient who underwent resection of an 8.5 cm × 8 cm × 4 cm retroperitoneal tumour, which eventually was diagnosed as PEComa of uncertain biological behaviour. Three years after the operation, the patient remains without any evidence of recurrence. A search was performed in the Medline and EMBASE databases for articles published between 1996 and 2018, and we identified 31 articles related to retroperitoneal and perinephric PEComas. We focused on sex, age, maximum dimension, histological and immunohistochemical characteristics of the tumour, follow-up and long-term outcome. Thirty-four retroperitoneal (including the present one) and ten perinephric PEComas were identified, carrying a malignant potential rate of 44% and 60%, respectively. Nearly half of the potentially malignant PEComas presented with or developed metastases during the course of the disease.

CONCLUSION

Retroperitoneal PEComas are not as indolent as they are supposed to be. Radical surgical resection constitutes the treatment of choice for localized disease, while mammalian target of the rapamycin (mTOR) inhibitors constitute the most promising therapy for disseminated disease. The role of mTOR inhibitors as adjuvant or neoadjuvant therapies needs to be evaluated in the future.

Perivascular Epithelial Cell Tumor of the Pancreas Diagnosed Preoperatively by Endoscopic Ultrasound-guided Fine-needle Aspiration

We herein report a 49-year-old woman with a perivascular epithelial cell tumor (PEComa) of the pancreas. Imaging studies demonstrated a relatively well-demarcated mass, measuring approximately 40 mm in diameter, located in the pancreatic tail. It was heterogeneously enhanced almost to the same degree as the surrounding pancreatic tissue in both the arterial and portal venous phases. We performed endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) using the Acquire^® 22-gauge needle and preoperatively obtained a definitive diagnosis with a sufficient sample. Clinicians should consider pancreatic PEComa in their differential diagnosis of patients with a pancreatic mass.

Primary hepatic perivascular epithelioid cell tumors: imaging findings with histopathological correlation

Background

Hepatic PEComas are very rare. Few systematic reports are available characterizing the imaging and pathological features of hepatic PEComa. The aim of this study was to investigate the imaging findings of primary hepatic perivascular epithelioid cell tumors (PEComa) and its correlation with histopathological features.

Methods

The CT, MRI and ultrasound images and pathological findings of 22 patients with primary hepatic PEComa were retrospectively reviewed.

Results

More females (14/22) were affected with the mean age of 47.1 years. Most patients (17/22) were asymptomatic and the routine laboratory tests were normal. More tumors occurred in the right lobe (13/22) with a mean diameter of 76.7 mm. Surgery was performed in 21 patients, and biopsy was performed in 1 patient. Immunohistochemical studies showed the expression rate of HMB-45 and Melan A was 100% (22/22) and 86.4% (19/22) within the tumor cells. The pathology diagnoses were angiomyolipoma (n = 18), lymphangioleiomyoma (n = 2), clear-cell myomelanocytic tumor of falciform ligament/ligamentum teres (n = 1), and not otherwise specified (n = 1). Fifteen cases were classified as uncertain malignant potential (n = 13) or malignant (n = 2). CT, MRI and ultrasound features included well-defined margins (19/22), internal heterogeneity (20/22), arterial enhancement (20/22), dysmorphic vessels (17/22), fat (9/22), hemorrhage (3/22), necrosis (8/22), and calcification (2/22). The diagnostic accuracy was only 27.3% (6/22). No local recurrence or metastasis was found in the follow-up patients (12/22).

Conclusions

On CT, MRI and ultrasound images, most hepatic PEComas are well-defined, heterogeneous, arterial enhanced masses with dysmorphic vessels, with or without fat, especially in middle-aged females. With the potential to be malignant, timely surgical resection and long-term follow-up may be helpful for improving the prognosis.

Malignant hepatic vascular tumors in adults: Characteristics, diagnostic difficulties and current management

Malignant vascular tumors of the liver include rare primary hepatic mesenchymal tumors developed in the background of a normal liver parenchyma. Most of them are detected incidentally by the increased use of performing imaging techniques. Their diagnosis is challenging, involving clinical and imaging criteria, with final confirmation by histology and immunohistochemistry. Surgery represents the mainstay of treatment. Liver transplantation (LT) has improved substantially the prognosis of hepatic epithelioid hemangioendothelioma (HEHE), with 5-year patient survival rates of up to 81%, based on the European Liver Intestine Transplantation Association-European Liver Transplant Registry study. Unfortunately, the results of surgery and LT are dismal in cases of hepatic angiosarcoma (HAS). Due to the disappointing results of very short survival periods of approximately 6-7 mo after LT, because of tumor recurrence and rapid progression of the disease, HAS is considered an absolute contraindication to LT. Recurrences after surgical resection are high in cases of HEHE and invariably present in cases of HAS. The discovery of reliable prognostic markers and the elaboration of prognostic scores following LT are needed to provide the best therapeutic choice for each patient. Studies on a few patients have demonstrated the stabilization of the disease in a proportion of patients with hepatic vascular tumors using novel targeted antiangiogenic agents, cytokines or immunotherapy. These new approaches, alone or in combination with other therapeutic modalities, such as surgery and classical chemotherapy, need further investigation to assess their role in prolonging patient survival. Personalized therapeutic algorithms according to the histopathological features, behavior, molecular biology and genetics of the tumors should be elaborated in the near future for the management of patients diagnosed with primary malignant vascular tumors of the liver.

Recurrence of retroperitoneal localized perivascular epithelioid cell tumor two years after initial diagnosis: case report

CONTEXT

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal tumors. Adjuvant radiotherapy and/or chemotherapy are administered according to the patient's clinical characteristics.

CASE REPORT

A 42-year-old female patient was operated to treat a retroperitoneal mass. The diagnosis was established as PEComa with benign behavior. Two years after the diagnosis, chest and abdominal computed tomography scans showed intra-abdominal recurrence and lymphangioleiomyomatosis in the lung. Treatment with everolimus was started. The disease stabilized in the third month of treatment, according to the response evaluation criteria in solid tumors.

CONCLUSION

PEComas are tumors with unpredictable behavior. Therefore, these patients require long-term follow-up, even in cases of correct diagnosis and benign PEComa.

Thoracoabdominal imaging of tuberous sclerosis

Imaging of tuberous sclerosis complex has rapidly evolved over the last decade in association with increased understanding of the disease process and new treatment modalities. Tuberous sclerosis complex is best known for the neurological symptoms and the associated neuroimaging findings, and children with tuberous sclerosis complex require active surveillance of associated abnormalities in the chest, abdomen and pelvis. Common findings that require regular imaging surveillance are angiomyolipomas in the kidneys and lymphangioleiomyomatosis in the chest. However multiple rarer associations have been attributed to tuberous sclerosis complex and should be considered by radiologists reviewing any imaging in these children. In this review the authors discuss the spectrum of imaging findings in people with tuberous sclerosis complex, focusing on MR imaging findings in the chest, abdomen and pelvis.

Primary pancreatic perivascular epithelioid cell tumor (PEComa): A surgical enigma. A systematic review of the literature

BACKGROUND

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor, with distinctive morphology and expression of myo-melanocytic markers. Current scientific literature reported just 24 cases of pancreatic PEComas. With our systematic review, we aimed at improving our understanding of the disease, focusing on the knowledge gained on epidemiology, etiology, clinical presentation, diagnosis, treatment and prognosis.

METHODS

Based on the PRISMA guidelines, a systematic research was carried out on PubMed/MEDLINE, Web of Science, Scopus, EMBASE, and EBSCO using the search terms: ("perivascular epithelioid cell tumor" OR ″PEComa") and ("pancreas "OR″ pancreatic").

RESULTS

The 4th-6th decades of life and female sex (86.9%) turned out as the most affected. Pancreatic head was the most involved site (50%), with a single lesion in almost all cases. The diagnosis was only obtained after histopathological examination (70.8%). The clinical presentation was non-specific, abdominal pain being the main symptom (60.9%). At immunohistochemistry, PEComa showed benign epithelioid predominance and a strong positivity for HMB-45, Melan-A, and α-SMA. Surgical resection was performed in almost all cases, while for one patient the multidisciplinary group chose just endoscopic and imaging follow-up, based on the benign nature of the lesion.

CONCLUSIONS

The biological characteristics of pancreatic PEComa remain an enigma. Its prognosis seems to depend on whether atypical ("worrisome") histological features are available or not. Surgery turned out as the most appropriate treatment, without reaching any agreement on surgery timing. Further studies on larger population are needed to better understand the biological features of pancreatic PEComa, in order to set up guidelines in the diagnosis, treatment and follow-up.

Diagnostic Accuracy of Amino Acid and FDG-PET in Differentiating Brain Metastasis Recurrence from Radionecrosis after Radiotherapy: A Systematic Review and Meta-Analysis

BACKGROUND

Current studies that analyze the usefulness of amino acid and FDG-PET in distinguishing brain metastasis recurrence and radionecrosis after radiation therapy are limited by small cohort size.

PURPOSE

Our aim was to assess the diagnostic accuracy of amino acid and FDG-PET in differentiating brain metastasis recurrence from radionecrosis after radiation therapy.

DATA SOURCES

Studies were retrieved from PubMed, Embase, and the Cochrane Library.

STUDY SELECTION

Fifteen studies were included from the literature. Each study used PET to differentiate radiation necrosis from tumor recurrence in contrast-enhancing lesions on follow-up brain MR imaging after treating brain metastasis with radiation therapy.

DATA ANALYSIS

Data were analyzed with a bivariate random-effects model. Sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio were pooled, and a summary receiver operating characteristic curve was fit to the data.

DATA SYNTHESIS

The overall pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, and diagnostic odds ratio of PET were 0.85, 0.88, 7.0, 0.17, and 40, respectively. The area under the receiver operating characteristic curve was 0.93. On subgroup analysis of different tracers, amino acid and FDG-PET had similar diagnostic accuracy. Meta-regression analysis demonstrated that the method of quantification based on patient, lesion, or PET scan (based on lesion versus not, P = .07) contributed to the heterogeneity.

LIMITATIONS

Our study was limited by small sample size, and 60% of the included studies were of retrospective design.

CONCLUSIONS

Amino acid and FDG-PET had good diagnostic accuracy in differentiating brain metastasis recurrence from radionecrosis after radiation therapy.

Primary Hepatic Neoplasms of Vascular Origin: Key Imaging Features and Differential Diagnoses With Radiology-Pathology Correlation

OBJECTIVE

This article describes, illustrates, and correlates imaging and pathologic features of primary vascular mesenchymal neoplasms of the liver, which arise from the vascular endothelium and perivascular epithelioid cells.

CONCLUSION

Familiarity with the spectrum of benign, malignant-potential and malignant vascular neoplasms, and nonneoplastic mimickers allows consideration in the differential diagnosis of enhancing hepatic masses. Understanding relevant pathologic features facilitates recognition of key imaging features, specifically dynamic contrast enhancement patterns on CT and MRI, which provide a useful classification system.

Hepatic perivascular epithelioid tumor (PEComa). A case report

A 37-year-old female had liver nodules found in an abdominal ultrasound scan. The radiological features were suggestive of hepatocellular adenomas, although there were some atypical findings. Two years later, one of the nodules showed dimensional progression and intralesional hemorrhage. The patient underwent a left hepatectomy and the postoperative course was uneventful. The histological exam and the immunohistochemistry were consistent with the diagnosis of PEComa. The PEComa is a mesenchymal tumor rarely described in the liver. The preoperative diagnosis of PEComa is very difficult and, with this report, the authors intend to increase the limited knowledge relating to natural history and optimal treatment of this rare condition.

Radiological findings of two neoplasms with perivascular epithelioid cell differentiation

Perivascular epithelioid cell tumors (PEComas) constitute a rare subset of mesenchymal neoplasms classified by the World Health Organization in 2002. We present two cases of PEComas; the first is a cervical PEComa in a 35-year-old woman with no known past medical history who presented with a palpable pelvic mass; the second is an adnexal PEComa in a 39-year-old woman with a history of colitis who presented with abdominal pain and diarrhea. The rarity of these tumors has led to little information about imaging characteristics which we hope these two cases will help expand.

Two cases of perivascular epithelioid cell tumor of the uterus: clinical, radiological and pathological diagnostic challenge

Background

Perivascular epithelioid cell tumor (PEComa) is a rare subtype of mesenchymal origin tumor composed of epithelioid cells which exhibits immunohistochemical co-expressions of melanocytic markers and smooth muscle markers.

Case presentation

In the first case, malignant uterine PEComa with vaginal and multiple lung metastasis was misdiagnosed preoperatively as uterine leiomyosarcoma despite a preoperative punch biopsy and immunohistochemical analysis of the metastatic vaginal mass. In the second case, synchronous uterine PEComa showing benign histology with lymph node involvement was incidentally detected after a staging operation for ovarian cancer. Definitive diagnosis of uterine PEComa was achieved only after hysterectomy despite preoperative assessment with pelvic magnetic resonance imaging and punch biopsy of metastatic lesion.

Conclusion

The authors report two rare cases of uterine PEComa diagnosed postoperatively based on the morphologic and immunohistochemical features.

Computerized Tomography and Magnetic Resonance Imaging Findings in Malignant Perivascular Epithelioid Cell Tumors of the Ovaries with Pulmonary Metastasis

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor composed of immunohistochemically and histologically distinctive perivascular epithelioid cells. Here, we report on the computed tomography (CT) and magnetic resonance imaging (MRI) findings of ovarian PEComa with pulmonary metastasis. The tumor was visible as a multilocular hemorrhagic mass that encased the ovarian vessels. These findings were different to those of other common ovarian tumors.

A systematic review: perivascular epithelioid cell tumor of gastrointestinal tract

Perivascular epithelioid cell tumor (PEComa) is a rare entity with distinctive morphology and of expressing myomelanocytic markers. Gastrointestinal tract (GI) is one of the most common anatomic sites of origin and counts for 20% to 25% of all reported cases of perivascular epithelioid cell tumors not otherwise specified (PEComas-NOS). However, the biologic behavior of perivascular epithelioid cell tumors of gastrointestinal tract (GI PEComas-NOS) is still unclear. The aim of conducting this systematic review is to sum up what is known so far of the epidemiology, natural history, management and prognosis of GI PEComas-NOS.A systematic research was performed on PubMed and EMBASE using the following terms: ("perivascular epithelioid cell tumor" or "PEComa") and ("gastrointestinal tract" or "GI" or "oral " or "mouth" or "esophagus" or "gullet" or "gastric" or "stomach" or "duodenum" or "jejunum" or "ileum" or "cecum" or "colon" or "colorectal" or "sigmoid" or "rectum" or "anus" or "mesentery") up to December 1, 2015. Retrieved GI PEComas-NOS publications, which included these terms, contains case reports, case series to case characteristic researches.A total of 168 articles were reviewed, 41 GI PEComa-NOS English studies among which were retrieved for analysis. We reviewed epidemiology, natural history, management and prognosis of GI PEComa-NOS. Generally GI PEComa-NOS is believed to have women predomination. The most frequently involved location is colon with non-specific clinical signs. Pathologically, GI PEComas-NOS shows epithelioid predominance (70%), meanwhile coexpresses melanocytic and muscle markers characteristically, while immunohistochemistry is a useful tool for identify, which indicates that HMB-45 is regarded as the most sensitive reagent. Complete resection served as mainstay of treatment, while chemotherapy should be unanimously considered to apply in malignant cases. Eventually, it is necessary for closed and long-term follow-up with endoscope and imaging for ruling out local recurrence or distant metastasis of this tumor.GI PEComas-NOS lives with unclear behavior. There are still many unverified clinicopathological issues of GI PEComas-NOS that needs to be clarified. Further studies and analyses concerning this rare entity should be brought out. Thus, the randomized clinical researches (RCTs) are required to be conducted.

Radiological findings of perivascular epithelioid cell tumour (PEComa) of the falciform ligament

Perivascular epithelioid cell tumour (PEComa) encompasses a group of mesenchymal tumours composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. A subset of PEComa that typically arises from the falciform ligament and/or ligamentum teres is termed clear cell myomelanocytic tumour of the falciform ligament/ligamentum teres. To date, its imaging findings have not been described. Here, we report the first radiological description of a pathologically confirmed tumour. The patient was a 5-year-old girl with a palpable abdominal mass. US, CT, MR and FDG-PET revealed a midline, well-defined, solid anterior abdominal wall tumour below the rectus abdominis and contiguous with the umbilicus that was hypervascular and FDG avid. Awareness of these imaging findings facilitates the diagnosis of this distinctive tumour.

Hepatic multiple perivascular epithelioid cell neoplasm: A case report and literature review

Perivascular epithelioid cell neoplasm (PEComa) is a rare tumor type and primary hepatic multiple perivascular is rarer still. The present case report investigated the case of a 40-year-old woman who was admitted to The Second Xiangya Hospital for hepatic multiple tumor by physical examination without any history of abdominal pain or body weight loss. Abdominal plain computed tomography revealed three lesions in the liver. All lesions exhibited a well-defined boarder and only one mass contained fatty tissue in S6 of the liver. An enhanced scan revealed that all lesions were heterogeneous, and were enhanced on the artery phase and on portal vein phase. On delay phase, the lesions revealed continued enhancement, which is isoattenuating to the normal hepatic parenchyma. Following excision of the three masses, the patient was pathologically diagnosed with hepatic multiple PEComa. Short-term re-examination revealed no recurrence.

Perirenal PEComa: Computed Tomography Findings and Differential Diagnosis

The World Health Organization defines perivascular epithelioid cell tumors (PEComas) as mesenchymal tumors and tumor-like conditions composed of epithelioid cells with a perivascular distribution. These tumors may show benign or malignant histology and/or biological behavior. However, the pathological features of malignancy may not correlate with biologic aggressiveness, and the criteria for malignancy are not clearly defined. Abdominopelvic PEComas are very rare and have been reported in various locations, including kidney, liver, pancreas, gastrointestinal tract, genitourinary tract, peritoneum, and retroperitoneum. Cross-sectional imaging techniques, including computed tomography (CT) may play an important role in the accurate detection and characterization of these tumors. We present the third case of an extremely rare PEComa with perirenal location, discuss CT findings and differential diagnosis.

Hepatic falciform ligament clear cell myomelanocytic tumor: A case report and a comprehensive review of the literature on perivascular epithelioid cell tumors

Background

The objective of the study was to explore the clinical expression, radiological and pathological features, differential diagnosis, and biological behavior of a clear cell myomelanocytic tumor. In a case involving a clear cell myomelanocytic tumor located in the hepatic falciform ligament, we evaluated clinical expression, radiological characteristics, histopathology, immunohistochemistry, and biological behavior; we also reviewed the relevant literature.

Case presentation

Clear cell myomelanocytic tumor is a benign soft-tissue neoplasm that often occurs in women, and is expressed as a painless mass. The falciform ligament is its most frequent site of occurrence. The imaging characteristics of this lesion were uneven enhancement in the arterial phase, continuing to strengthen in the venous phase, and equal density in the balance phase. Histological and immunohistochemical analysis revealed the main transparent epithelioid cells and smooth muscle spindle cells to be HMB-45(+), smooth muscle actin(+), and melan-A (+).

Conclusion

Hepatic vascular epithelioid cell tumors are very rare mesenchymal neoplasms. Few studies have investigated this tumor in the hepatic falciform ligament; consequently, its diagnosis and the selection of an appropriate treatment and follow-up protocol are challenging. Treatment outcome remains unpredictable. Therefore, clear cell myomelanocytic tumor should be viewed as a tumor with uncertain malignant potential requiring long-term follow-up.

PEComa of the terminal ileum mesentery as a secondary tumour in an adult survivor of embryonal rhabdomyosarcoma

Perivascular epithelioid cell tumours (pecomas) are rare mesenchymal tumours that are characterized by perivascular epithelioid cell differentiation and immunoreactivity to myogenic and melanocytic markers. These tumours can be classified as benign, uncertain malignant potential, or malignant. Because of the rarity of pecomas, their cause and clinical prognosis remain unclear. To the best of our knowledge, no reports in the literature describe a pecoma of the terminal ileum mesentery as a secondary tumour in an adult survivor of childhood embryonal rhabdomyosarcoma, let alone any childhood cancer. Here, we present the case of a 27-year-old man with a pecoma involving the mesentery of the terminal ileum. At the age of 5, he had been treated with a combination of chemotherapy and high-dose pelvic radiation therapy for embryonal rhabdomyosarcoma, most likely arising from the posterior bladder wall. During routine follow-up 22 years after this patient's initial treatment, computed tomography imaging revealed a mass within the terminal ileum mesentery. The tumour was successfully treated with surgical resection, and pathology examination determined the mass to be a pecoma with uncertain malignant potential. This first case of a pecoma of the terminal ileum mesentery arising within a high-dose radiation therapy field as a secondary tumour in an adult survivor of childhood cancer highlights the importance of screening and surveillance in high-risk childhood cancer survivors treated with high-dose radiation therapy. Further research to build a better understanding of this remarkably rare tumour is warranted.

Laparoscopic excision of infra-renal PEComa

Perivascular epitheloid cell tumors (PEComas) are rare tumors of malignant potential. There is no normal cell variant to these cells. The family is large and includes angiomyolipoma, clear cell “sugar” tumor amongst others. Imaging modalities are not very diagnostic. The diagnosis hence is often postoperative. A 55-year old female presented to us with ultrasonographic diagnosis of solid mass in the right infrarenal region. Contrast-enhanced computerized sonography (CECT) suggested paraganglioma or a soft tissue retroperitoneal tumor. Laparoscopic excision was successful. The rarity of this pathology and laparoscopic modality of excision prompted us to publish this report.

Primary retroperitoneal perivascular epithelioid cell neoplasm: A case report

Perivascular epithelioid cell neoplasm (PEComa) is a rare type of tumor, and primary retroperitoneal PEComa is rarer still. The present report discusses the case of a 51-year-old woman who was admitted to hospital following stiffness and discomfort in the upper right abdomen for longer than one month. Computed tomography identified a soft tissue mass in the rear right kidney, accompanied by clear cystic degeneration and bleeding. The borderline between the mass and the right kidney was not distinct. An enhanced scan revealed that the solid section of the mass was progressively enhanced. Following excision of the mass and the affected right kidney, the patient was pathologically diagnosed with retroperitoneal PEComa involving the right kidney. Short-term reexamination did not detect any recurrence.

Malignant perivascular epithelioid cell tumor arising in the mesentery: A case report

Primary perivascular epithelioid cell tumors (PEComas) of the mesentery are rare; therefore, the clinical and imaging features of the tumor have yet to be adequately investigated. The present study reports the case of a 48-year-old female patient histologically diagnosed with a PEComa arising in the mesentery of the small bowel. Abdominal plain computed tomography (CT) identified a large, partially ill-defined and heterogeneous mass with a size of 12.5×8.5-cm occupying the lower abdomen. Upon contrast-enhanced CT imaging, the tumor displayed nonhomogeneous contrast-enhancement with hypodense areas, and multiple tumor vessels were observed during arterial phase imaging. In conclusion, the present study proposed that PEComas should be considered in the differential diagnosis of lesions arising in the mesentery; however, differentiation based on imaging criteria alone can be difficult.

Imaging features of primary and metastatic malignant perivascular epithelioid cell tumors

OBJECTIVE

The objective of our study was to describe the imaging features of primary and metastatic malignant perivascular epithelioid cell tumors (PEComas).

MATERIALS AND METHODS

In this retrospective study, 36 patients (26 women, 10 men; mean age, 53.1 years; age range, 35-77 years) with a histopathologically confirmed diagnosis of malignant PEComa who were seen at our institute between January 2007 and December 2012 were included. Pretreatment imaging of the primary tumor in 17 patients (CT, n = 13; MRI, n = 9; ultrasound, n = 5) and follow-up imaging in all 36 patients (CT, n = 36; MRI, n = 7) were reviewed by three radiologists in consensus.

RESULTS

The most common site of presentation of malignant PEComas was the retroperitoneum (38.9%) followed by the female genital tract (27.8%). Kidneys (8/36) and uterus (8/36) were the organs most frequently involved. The mean largest dimension was 11.01 cm (range, 4.5-25 cm). Primary tumors were well-circumscribed masses (16/17), were heteroechoic on ultrasound (5/5), were hypodense (2/6) to isodense (4/6) enhanced significantly (11/12) and compared with the paraspinal muscles on CT, were hypointense to isointense compared with skeletal muscle on T1-weighted imaging (8/9), were heterogeneously hyperintense compared with skeletal muscle on T2-weighted imaging (9/9), and showed significant post-gadolinium enhancement (7/7) on MRI. Of the 17 primary tumors, necrosis was seen in seven tumors, hemorrhage in three tumors, and calcification in three tumors. Twenty-six of 36 (72%) patients developed metastases, most commonly to the lung (21.6%), liver (17.6%), and peritoneum (10.8%).

CONCLUSION

Malignant PEComas in our study were large tumors that most often arise in the kidneys and uterus and metastasize to lungs, liver, or peritoneum. In our experience malignant PEComas should be considered in the differential diagnosis of large well-circumscribed renal and uterine tumors.

Perivascular epitheloid cell tumor (PEComa) mimicking retroperitoneal liposarcoma

PEComas are a collection of generally rare tumors, defined by the World Health Organization as ‘mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epitheloid cells’. We describe the case of retroperitoneal PEComa with a liposarcoma-like appearance on cross-sectional imaging, but distinctive immunohistochemistry revealing the correct diagnosis.

PEComa: A Perivascular Epithelioid Cell Tumor in the Liver-A Case Report and Review of the Literature

Perivascular epithelioid cell tumors are soft tissue tumors that can occur in various locations in the body whose incidence is rising. Hepatic PEComas are quite rare and diagnosis involves positivity of Melan-A and HMB45 on immunohistochemistry. Usual treatment is surgery for benign tumors and chemotherapy including mTOR inhibitors for malignant tumors. Here we discuss the radiological and pathological diagnosis, evaluation, and management of a hepatic PEComa. We describe a 51-year-old patient who was diagnosed incidentally after unusual physical exam findings.