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Perivascular epithelioid cell tumors (PEComas) are a group of rare mesenchymal tumors, which demonstrate varied imaging appearances and treatment options. These tumors may arise de novo or in the setting of systemic disorders, such as tuberous sclerosis. Some PEComas are benign and easily resected while others may represent systemic or metastatic disease with limited therapeutic options. The purpose of this review is to introduce the topic of perivascular epithelioid cell tumors and the most common tumors within the PEComa family as well as discuss the epidemiology, morphology, radiographic appearance, and treatment options of these rare tumors., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: To describe the clinical and ultrasonographic features of uterine perivascular epithelioid cell tumor (PEComa) using standardized terminology., Methods: This was a retrospective analysis of patients with uterine PEComa diagnosed and confirmed by pathology and immunohistochemistry at West China Second University Hospital, Sichuan University, Sichuan, China, between January 2010 and September 2023. The Morphological Uterus Sonographic Assessment (MUSA) consensus and the International Endometrial Tumor Analysis (IETA) consensus were utilized for the standardized description of the sonographic characteristics of uterine PEComa. We summarized the clinical and ultrasound features of uterine PEComa in cases from our center and those found in a review of the literature conducted using PubMed from 1 January 2013 to 30 September 2023 (inclusive)., Results: Five patients, aged 33-57 (median, 52) years, with a total of six uterine PEComa lesions were included in our cohort. All cases had complete ultrasonographic and pathological images. None of the patients had a history of tuberous sclerosis complex. Two patients had malignant PEComa (one patient had two lesions) and three had benign PEComa, originating from the cervix, myometrium or uterine cavity. Patients presented with symptoms including increased vaginal discharge, vaginal bleeding and pelvic or abdominal pain. The three patients with benign PEComa underwent total hysterectomy and bilateral adnexectomy, tumor excision and conservative management, respectively, while both malignant cases underwent total hysterectomy and bilateral adnexectomy followed by chemotherapy. Regular follow-up (from 6 to 24 months) revealed recurrence in one case. Two lesions were misdiagnosed as uterine fibroids, two as cervical cancer, one as metastatic cervical cancer (with myometrial invasion) and one was indeterminate. Ultrasound examination showed that most lesions displayed regular round or ovoid shape (66.7%), uniform echoes (66.7%) and hypoechogenicity (66.7%), with one (16.7%) malignant PEComa showing cystic areas and one (16.7%) benign PEComa showing punctate calcifications. All lesions lacked shadowing and the majority showed moderate to abundant vascularity (color score of 3-4, 83.3%). The color score was 2-4 in the periphery in 100% of cases and internally in 83.3% of cases. The three benign PEComas showed similar characteristics in vascular distribution, with scattered internal vessels and peripheral vessels exhibiting a circular pattern. The literature search identified 11 articles describing the ultrasonographic appearance of 18 cases of uterine PEComa, with similar characteristics to those in our cohort., Conclusions: The sonographic features of uterine PEComa include a uniform or non-uniform hypoechogenic mass, typically round or ovoid with regular margins, occasionally containing cystic areas or calcifications, lacking shadowing and often showing moderate to abundant vascularity. Although the preoperative ultrasound diagnosis of uterine PEComa remains challenging, particularly given the non-specific nature of the sonographic characteristics described here, dispersed intratumoral vessels and a peripheral circular vascular distribution may serve as diagnostic clues for uterine PEComa, but more cases are needed for confirmation. © 2024 International Society of Ultrasound in Obstetrics and Gynecology., (© 2024 International Society of Ultrasound in Obstetrics and Gynecology.)

Introduction: Perivascular epithelioid cell tumors are uncommon mesenchymal tumors. The genital tract is the most common extrarenal location. Preoperative diagnosis is rarely achieved owing to non-specific symptoms and imaging features. Consensus on treatment strategies remains elusive. Case presentation We report the case a 38 year-old north African woman with a primary sterility, who was diagnosed with a uterine Perivascular epithelioid cell tumor of uncertain malignant potential on a resection specimen of an intracavity polypoid mass. Immunohistochemistry confirmed the diagnosis and we opted for conservative surgery to preserve the patient's fertility desires., Conclusion: Uterine perivascular epithelioid cell tumor is a rare entity that warrants consideration in the differential diagnosis of uterine tumors. Treatment modalities, follow-up protocols, and prognosis remain ambiguous. Given their unpredictable behavior, accurate diagnosis and long-term monitoring are imperative., (© 2024. The Author(s).)

Abstract: We compared 18 F-FAPI and 18 F-FDG PET/CT findings of metastatic perivacular epitheliod cell tumor in a 23-year-old woman. Apart from showing strong uptake of a left upper lung mass that showed moderate uptake on 18 F-FDG, 18 F-FAPI PET/CT additionally presented hypermetabolism in diffuse multifocal lesion throughout the body. This case suggests that 18 F-FAPI PET/CT might play a more beneficial role than 18 F-FDG PET/CT in identifying and assessing the extent of perivascular epithelioid cell tumors., Competing Interests: Conflicts of interest and sources of funding: none declared., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: We report the findings of 68 Ga-DOTATATE PET/CT in a 56-year-old woman with solitary pulmonary perivascular epithelioid cell tumor. 68 Ga-DOTATATE PET/CT showed a lesion with intense uptake in the region of pancreatic head and a solitary nodule with moderate uptake in the left lung. Pancreatic neuroendocrine tumor with pulmonary metastasis was considered. The postoperative pathological results showed a benign perivascular epithelioid cell tumor of the lung. This case emphasizes the need to increase awareness of benign perivascular epithelioid cell tumors in the differential diagnosis of solitary pulmonary nodule with moderate DOTATATE activity., Competing Interests: Conflicts of interest and sources of funding: none declared., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

A 33-year-old lady was referred to our clinic with a history of left upper eyelid swelling and difficulty to open her left eye for more than 4 years. Her globe was in infero-nasal displacement, and ocular movement was not full, with restriction to every direction. No clinical sign including eye redness, pain or visual loss was found on examination. Exophthalmometry confirmed 2 mm of left-sided proptosis. Computed tomography (CT) imaging of the orbit obtained in axial and coronal planes depicted an irregular and heterogeneous soft-tissue density mass in the left lacrimal gland, measuring 25 × 17 mm. Magnetic resonance imaging (MRI) revealed the mass of slightly longer T1 and slightly longer/shorter T2 signal, and Gd-enhanced MRI showed a significant enhancement. The tumor was first presumably diagnosed of pleomorphic adenomas. A surgery was applied to remove the tumor completely. Histopathological evaluation led to the diagnosis of PEComa.

In 2013, the World Health Organization defined perivascular epithelioid cell tumor (PEComa) as "a mesenchymal tumor which shows a local association with vessel walls and usually expresses melanocyte and smooth muscle markers." This generic definition seems to better fit the PEComa family, which includes angiomyolipoma, clear cell sugar tumor of the lung, lymphangioleiomyomatosis, and a group of histologically and immunophenotypically similar tumors that include primary extrapulmonary sugar tumor and clear cell myomelanocytic tumor. Clear cell tumors with this immunophenotypic pattern have also had their malignant variants described. When localizing to the liver, preoperative radiological diagnosis has proven to be very difficult, and most patients have been diagnosed with hepatocellular carcinoma, focal nodular hyperplasia, hemangioma, or hepatic adenoma based on imaging findings. Examples of a malignant variant of the liver have been described. Finally, reports of malignant variants of these lesions have increased in recent years. Therefore, we support the use of the Folpe criteria, which in 2005 established the criteria for categorizing a PEComa as benign, malignant, or of uncertain malignant potential. Although they are not considered ideal, they currently seem to be the best approach and could be used for the categorization of liver tumors., Competing Interests: Conflict-of-interest statement: The author reports no relevant conflicts of interest for this article., (©The Author(s) 2024. Published by Baishideng Publishing Group Inc. All rights reserved.)

Introduction: Perivascular Epithelioid Cell tumor (PEComa) is a rare mesenchymal neoplasm characterized by the co-expression of melanocytic and myoid markers. While PEComas can arise in diverse anatomical sites, gastric PEComas are exceedingly rare, with merely nine cases documented in the extant literature., Case Presentation: Herein, we have presented a case of gastric PEComa in a 65-year-old male patient who exhibited a 3-year history of epigastric pain, with notable exacerbation in the two months prior to diagnosis. For the initial evaluation of the patient's condition, Endoscopic Ultrasound-guided Fine Needle Aspiration (EUS-FNA) and Computed Tomography (CT) were employed, which enabled a preoperative diagnosis. Radiological assessment demonstrated a neoplasm exhibiting heterogeneous arterial enhancement, persistent delayed enhancement, and distinct margins. Subsequent to diagnosis, the patient underwent surgical resection and has maintained a disease-free status for one year postoperatively. This case report highlights the crucial role of EUS-FNA in facilitating preoperative histological diagnosis and optimizing surgical planning for gastric PEComa., Conclusion: This case constitutes the tenth documented instance of gastric PEComa in the global literature. In this case, EUS-FNA facilitated a preoperative histopathological diagnosis, thereby enabling precise surgical planning. An accurate preoperative diagnosis is crucial for devising an optimal treatment strategy., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Hepatic PEComa are tumors that show perivascular epithelioid cell differentiation. Scarcely published, its management is based on small case series and currently its treatment of choice is surgical resection. We present a clinical case of a 74-year-old woman who underwent surgery at our hospital for a benign hepatic PEComa.

Perivascular epithelioid cell tumors (PEComa) are rare mesenchymal neoplasms that arise from soft tissue of various organs such as the stomach, intestines, and lungs. We report a rare case of a primary PEComa of the liver and its characteristics on contrast-enhanced ultrasound (CEUS) in a 51-year-old female patient with an incidental finding of a hypoechoic liver lesion with peripheral hypervascularization on Doppler ultrasound. CEUS showed homogenous hypervascularity in the arterial phase that was consistent in the portal phase. In the late phase, a central washout phenomenon was evident. Histopathologic findings on sonographic biopsy of the lesion revealed a mesenchymal tumor with positivity for melanocytic markers Human Melanin Black-45 (HMB45) and Melan-A consistent with a PEComa. Despite the absence of high-risk features for malignancy, surgical resection was recommended due to the uncertain malignant potential of PEComas. The patient refused the operation and preferred sonographic follow-up; the lesion was stable over a period of 2 years. CEUS can provide valuable information regarding PEComa. After histological confirmation, the choice between resection and a watchful waiting must be made on individual basis., (© 2023. The Author(s).)

Rationale: Neoplasms with perivascular epithelioid cell differentiation (PEComas) are mesenchymal tumors that rarely occur in the colon. Here, we report the occurrence of a malignant PEcoma in the colon using 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT)., Patient Concerns: A 55-year-old woman was admitted to the hospital with abdominal pain for 10 days and a self-induced abdominal mass for 3 days. 18F-FDG PET/CT imaging showed a large hypermetabolic nodule and mass in the right mid-upper abdomen with heterogeneous density and a further increase in metabolism on the delayed scan., Diagnoses: PEComa of the colon., Interventions: Tumor resection was performed., Outcomes: The patient is well after 2 months of treatment, pending further follow-up., Lessons: Malignant perivascular epithelioid cell tumors originating in the colon are extremely rare, and our report suggests that PEComa should be considered as a differential diagnosis for 18F-FDG gastrointestinal malignancies. Additionally, 18F-FDG PET/CT may play a key role in the staging and extent of lesions in intestinal malignancies., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2023 the Author(s). Published by Wolters Kluwer Health, Inc.)

Background: Perivascular epithelioid cell tumor (PEComa) is a mesenchymal tumor with distinct histologic and immunologic features. PEComas that originate in the bladder are extremely rare clinically, with only 35 cases reported in the English literature thus far. Here, we report a case of bladder PEComa resection by transurethral en bloc resection of bladder tumor (ERBT)., Case Presentation: A 66-year-old female with a history of poorly controlled type 2 diabetes with associated complications of frequent urinary tract infections presented to our hospital for a routine physical examination. Outpatient ultrasound examination revealed a strong echogenic mass of approximately 1.5 × 1.3 × 1.3 cm in size on the posterior wall of the bladder. The enhanced computed tomography and enhanced magnetic resonance imaging after admission both suggested a well-defined isolated nodular mass on the posterior wall of the bladder with significant enhancement on the enhanced scan. The tumor was successfully and completely resected by ERBT. Postoperative pathological examination and immunohistochemical results confirmed the mass was a bladder PEComa. No tumor recurrence was observed in the six-month postoperative follow-up., Conclusion: Bladder PEComa is an extremely rare mesenchymal tumor of the urinary system. When imaging and cystoscopy reveal a nodular mass with an abundant blood supply in the bladder, PEComa should be included in the differential diagnosis of bladder tumors. Surgical resection is currently the primary option for the treatment of bladder PEComa. For a solitary, pedunculated, narrow-based, small-sized bladder PEComa, resection of the tumor by ERBT was a safe and feasible approach in our patient and may be considered for similar cases in the future., (© 2023. The Author(s).)

Perivascular epithelioid cell tumors, also known as PEComas, are rare mesenchymal tumors composed mainly of epithelioid cells found in perivascular tissue. PEComas occur most frequently in the kidney, uterus, the gastrointestinal tract, liver, and retroperitoneum; those originating in the biliary tree are extremely rare. We report a case of benign PEComa of the cystic duct with positive TFE3 staining on immunohistochemistry.A 66-year-old woman was referred for a 20 mm mass adjacent to the common bile duct discovered incidentally on abdominal ultrasound. Laboratory data including tumor markers were unremarkable. The tumor appeared to arise from the cystic duct, showed early enhancement, and compressed the common bile duct on imaging studies. Endoscopic ultrasound-guided fine-needle aspiration revealed round- and spindle-shaped atypical cells with eosinophilic cytoplasm and brown deposits suggestive of melanin granules. Histological examination of the resected specimen revealed a tumor consisting of epithelioid cells forming an alveolar structure, with melanin pigmentation. Immunohistochemistry was positive for HMB-45 and TFE3, consistent with benign pigmented PEComa of the cystic duct. Melanotic, myogenic, and TFE3 staining are helpful when diagnosing PEComas arising in unusual locations., (© 2022. Japanese Society of Gastroenterology.)

Perivascular epithelioid cell neoplasm (PEComa) is a rare type of tumour, and primary retroperitoneal PEComa is rarer still. Although pulmonary lymphangioleiomyomatosis (LAM), angiomyolipomas and clear cell 'sugar' tumours of the lung are well described, relatively little is known about other members of the PEComa family. We describe a case of an asymptomatic retroperitoneal PEComa, lymphangioleiomyoma type, which appeared in a previously healthy middle-aged woman as an incidental finding, in a CT scan performed in the context of spontaneous pneumothorax. The patient underwent surgical excision of the tumour and the histopathological and immunohistochemical analysis of the surgical specimen made the definitive diagnosis. Although rare, reports of isolated retroperitoneal lymphangioleiomyoma and primary retroperitoneal PEComas NOS (not otherwise specified) are described in the literature, normally associated with pulmonary LAM. The patient's pulmonary imaging was normal. Short-term re-examination did not detect any recurrence. We also provide a literature review of this rare group of tumours., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Perivascular epithelioid cell tumors (PEComas) are a very rare group of neoplasms and were first reported in 1996. These tumors represent a family of mesenchymal neoplasms, related through activation of the mammalian target of rapamycin (mTOR) inhibitor signaling pathway. The objective of this case report is to demonstrate significant regression of the tumor after neoadjuvant treatment with an oral mTOR inhibitor, following surgical removal of the mass to avoid a multiorgan resection. We present a case of a 27-year-old female with retroperitoneal PEComa and evaluated the tumor with MRI and integrated 18F-FDG-PET/CT scans at presentation and serially during treatment with everolimus. After 6 months of treatment with everolimus the tumor showed a substantial size reduction. Therefore, a multiorgan resection could be omitted. The patient has not demonstrated any disease recurrence after nearly 2 years of follow-up. PEComas are tumors with unpredictable behavior. Our report indicates that treatment of PEComas with everolimus may achieve a significant clinical response. As indicated by our case and past reports, mTOR inhibitors may be one of the best treatment options for this disease.

Abstract: A 10-year-old girl with a right renal mass underwent 18 F-FDG PET/CT and 68 Ga-FAPI-04 PET/MRI for presurgical assessment of tumor invasion and malignant potential. The mass showed low 18 F-FDG uptake and intense 68 Ga-FAPI-04 uptake. Nephrectomy was performed, and the histopathologic diagnosis was aggressive PEComa (perivascular epithelioid cell tumor). This case showed that 68 Ga-FAPI-04 PET outperformed 18 F-FDG PET in detecting aggressive PEComa., Competing Interests: Conflicts of interest and sources of funding: none declared. This work is supported by the “234 Discipline Climbing Plan” of the First Affiliated Hospital of Naval Medical University (grant 2019YPT002, and 2020YPT002)., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

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., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms composed of spindled to epithelioid cells that co-express both melanocytic and myogenic markers. Recently, in 2018, a distinctive variant of PEComa has been described that arises in association with tuberous sclerosis complex (TSC) and resembles a fibroma by conventional morphology (called fibroma-like PEComa). Herein, we describe a case of a fibroma-like PEComa in a 4-year-old male child with a known diagnosis of tuberous sclerosis who presented with a firm mass along the anteromedial aspect of the right knee. The mass was excised, and microscopic examination showed bland spindled to stellate cells embedded in a dense collagenous stroma, morphologically resembling a fibroma. Immunohistochemistry analysis showed positivity for desmin (a myogenic marker) and HMB45 (a melanocytic marker), a hallmark for PEComas. To our knowledge, only six cases of fibroma-like PEComa have been described in the literature so far and this is the first report of such a tumor in the medial retinaculum of the knee joint with illustrations of conventional and diffusion imaging features. This case highlights the unique association of fibroma-like PEComa lesions with TSC. This should be considered a differential diagnosis for T2 hypointense masses in tuberous sclerosis patients. In addition, a diagnosis of fibroma-like PEComa should prompt further evaluation for associated TSC., (© 2021. ISS.)

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., (© 2022. The Author(s).)

Perivascular epithelioid cell tumours (PEComa) are rare tumours of mesenchymal origin. We report a 39-year-old patient who presented with painful defecation secondary to an anorectal mass. The diagnosis of anorectal PEComa was confirmed following excision and histopathological examination. We review the literature and discuss the management of this uncommon entity., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2022. No commercial re-use. See rights and permissions. Published by BMJ.)

Clear cell "sugar" tumor of the lung is a rare benign tumor arising from perivascular epithelioid cells (PECs). They belong to a group of mesenchymal neoplasms called PEComas. Although widely presumed as benign, due to their rich vascular stroma they are usually avid for the different types of contrast agents used in imaging studies, mimicking a malignant lesion. We report the case of a 66-year-old man in whom a solitary pulmonary nodule was discovered during oncological staging for an adenocarcinoma of the prostate who underwent an anatomical pulmonary segmentectomy. The final pathology result was a perivascular epithelioid cell tumor (pulmonary PEComa or clear "sugar" cell tumor).

Two male patients presented with painless vision loss to blindness in one eye, and the radiography examinations revealed an intraocular mass suspicious for choroidal melanoma. They underwent enucleation. The histopathological and immunohistochemical findings were compatible with the diagnosis of intraocular perivascular epithelioid cell tumor. Because of its rarity, intraocular perivascular epithelioid cell tumor is easy to be confused with other intraocular tumors on histopathological and immunohistochemical examinations. (Chin J Ophthalmol, 2021, 57: 857-860) .

A 39-year-old woman presented in the emergency ward for abdominal pain and acute anemiation. Abdominal-thoracic CT scan showed haemoperitoneum, with a parauterine mass and a pathological pulmonary pattern suspicious for lymphangioleiomyomatosis (LAM), a systemic disease belonging to perivascular epithelioid cell tumours (PEComas). Gynaecological ultrasound showed a hypoechoic irregular solid mass of the uterine right wall. Ultrasonographic virtual organ computer-aided analysis showed the mass completely formed by arteriovenous vessels, and that allowed distinction from leiomyosarcoma. Repeated haemoperitoneum required uterine artery embolisation. Mass revascularisation occurred in the following 7 days. A laparotomic hysterectomy with removal of the uterus and right parametrium was performed in epidural analgesia. Histological features were consistent with the diagnosis of uterine PEComa of uncertain malignant features, in the presence of coexisting pulmonary LAM. In women with LAM, acute haemoperitoneum may indicate the presence of a uterine PEComa whose diagnosis can be challenging., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2021. No commercial re-use. See rights and permissions. Published by BMJ.)

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., Competing Interests: Disclosure: The Disclosure of Potential Conflicts of Interest forms are provided with the online version of the article (http://links.lww.com/JBJSCC/B665)., (Copyright © 2021 by The Journal of Bone and Joint Surgery, Incorporated.)

Fibroma-like perivascular epithelioid cell (PEComa) tumor is an extremely rare family of mesenchymal tumors composed of cells co-expressing melanocytic and myogenic markers. To date, 13 cases of primary bone PEComa have been reported in the literature and five reported fibroma-like PEComas were found in the soft tissues of patients with tuberous sclerosis (TSC). However, no fibroma-like PEComa has been reported in bone, either sporadic or TSC-associated. Here we report the case of a 22-year-old man with known TSC, who presented for evaluation of an asymptomatic mass in his left fibula diaphysis that had been present for 5 years. He had no activity-related pain, numbness, weakness, or limitations in range of motion. Both 3-T MRI and CT demonstrated a tumor originating from the midshaft middiaphyseal fibula. Axial T1-weighted and fat-saturated T2-weighted fast spin echo images showed a well-defined lesion in the fibula with extension into the surrounding soft tissues. Whole body bone scan was negative for metastasis using technetium-99m. Renal ultrasound was unremarkable with no evidence of angiomyolipoma. Histopathology demonstrated isolated spindle cells in a dense collagenous matrix. By immunohistochemical staining, tumor cells were positive for HMB-45 and MiTF and partially positive for alpha-smooth muscle actin supporting a diagnosis of fibroma-like PEComa of the midshaft fibula. Although fibroma-like PEComa of bone is very rare, a bone tumor in the setting of TSC should raise suspicion for the diagnosis, in particular if histology demonstrates rare epithelioid cells in a densely fibrotic stroma.

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.

Abstract: A 38-year-old woman presented for 18F-FDG PET/CT after multiple intra-abdominal surgical resections of a rare recurrent perivascular epithelioid cell tumor of the gastrointestinal tract. A solitary pelvic metastasis was detected, but surprisingly exhibited neither increased glucose consumption nor contrast enhancement on CT. Follow-up 18F-FDG PET/CT staging in the further disease course revealed multiple abdominal metastases, now, however, with markedly increased 18F-FDG uptake and intraoperatively correlating widespread peritoneal sarcomatosis. This case gives preliminary insight into monitoring of disease progression in metastatic perivascular epithelioid cell tumor, although the underlying pathophysiological bases for varying 18F-FDG uptake in PET/CT are not yet fully understood., Competing Interests: Conflicts of interest and sources of funding: none declared., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms with unpredictable behavior. They are characterized by epithelioid cells, which stain with melanocytic markers, associated with spindle cells reactive for smooth muscle markers. PEComas may be sporadic or associated with the tuberous sclerosis complex, with mutations affecting mostly tuberous sclerosis complex (TSC) 2 and less frequently TSC1 genes. More recently a subtype of PEComa harboring TFE3 gene rearrangement, mutually exclusive with TSC complex mutations, has been identified. The bladder and the other genitourinary tract organs are an infrequent site of origin; to date, only 3 cases of primitive bladder PEComas, 1 prostatic PEComa, and 2 epithelioid angiomyolipomas of the kidney with TFE3 rearrangement have been described in literature. We report a bladder PEComa case with Xp11 rearrangement in a patient who previously had undergone chemotherapy for chronic lymphatic leukemia. We assessed the meaning of the presence of TFE3 rearrangement in genitourinary tract PEComas and the possible correlation of these uncommon lesions with previous chemotherapy. A better understanding of this entity's genetics may help suggest appropriate targeted therapy, which is still lacking in genitourinary tract PEComas., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Competing Interests: Competing interests: None declared.

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor with unique histological and immunohistochemical characteristics. Malignant renal cell carcinoma is even rarer and its biological behavior is still not clear. We report here a case of malignant PEComa in a male patient. The first symptom of the patient was intermittent hematuria. Ultrasound and computed tomography scan showed a solid mass in the left kidney. Fibrosarcoma was initially diagnosed after radical resection of the tumor. Six years later, the patient had a tumor recurrence and underwent a second operation, through which the diagnosis of renal malignant PEComa was made. Since then, the patient received chemotherapy, a third operation, and interventional treatment because of recurrence and metastasis of the tumor, which prolonged the life of the patient for another 6 years. Malignant PEComa involving the kidney is very rare; it seems to develop slowly but will recur and metastasize. At present, surgical resection remains the best treatment.

Background: Perivascular epithelioid cell tumours (PEComas) represent a rare group of mesenchymal tumours with an unpredictable outcome. They are usually observed in middle-aged women whilst they are very rare in children, with limited cases described. Due to the rare anatomical location in kidneys, a correct diagnosis and treatment is really challenging., Methods: We observed and treated a case of kidney's PEComa in a 14-year-old boy., Results: An individualized approach based on anatomical (3D CT-reconstructions) and histopathological (US-guided preliminary biopsy) features lead us to perform a successful robotic-sparing surgery enabling the preservation of two-thirds of the kidney involved., Conclusions: A meticulous preoperative planning in selected patients can lead to a minimally invasive approach even in some paediatric kidney's neoplasms., (© 2020 John Wiley & Sons Ltd.)

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.

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.

Chest CT images were acquired in a 67-year-old man to evaluate a left lung mass revealed by chest radiography. The image findings suggested possible pulmonary malignancy. FDG PET/CT was performed for staging, which showed the abnormally increased activity in the lung mass with hypermetabolic lymph node. Pathology from the biopsy confirmed malignant perivascular epithelioid cell tumor.

Background: Perivascular epithelioid cell tumor, an extremely rare mesenchymal tumor, could be ubiquitous but rarely arises from pancreas. Surgery is considered the most appropriate treatment. Nevertheless, activation of mTOR pathway seems to be a common pathogenic event in PEComas paving the way to chemotherapy by mTOR inhibitor., Method: A 17 year-old man presented a hypervascular tumor of 55 mm, located in the head of pancreas without bile duct or pancreatic duct compression., Results: Histopathology showed epithelioid cells with clear or focally granular eosinophilic cytoplasm with melanocytic (HMB-45, Melan-A) and myoid markers which confirmed diagnosis of PEComa. Given the absence of worrisome feature, we ruled out surgery and decided to initiate treatment with Sirolimus, an mTOR inhibitor. After 3.5 years, we showed a significant reduction in size of the tumor., Conclusion: This first case of pancreatic PEComa treated by mTOR inhibitor without surgery suggests a good efficiency of this therapy., (Copyright © 2019 IAP and EPC. Published by Elsevier B.V. All rights reserved.)