PEC and sugar

Uterine Leiomyosarcoma Associated With Perivascular Epithelioid Cell Tumor: A Phenomenon of Differentiation/Dedifferentiation and Evidence Suggesting Cell-of-Origin

Perivascular epithelioid cell tumor (PEComa) is a mesenchymal tumor thought to originate from perivascular epithelioid cells (PECs). The normal counterpart to PEC, however, has not been identified in any human organ, and the debate as to whether PEComa is related to smooth muscle tumors has persisted for many years. The current series characterizes 4 cases of uterine leiomyosarcoma (LMS) coexisting with PEComas. All cases exhibited an abrupt transition from the LMS to PEComa components. The LMS component displayed typical spindled morphology and fascicular growth pattern and was diffusely positive for desmin and smooth muscle myosin heavy chain, completely negative for HMB-45 and Melan A, and either negative or had focal/weak expression of cathepsin K and GPNMB. In contrast, the PEComa tumor cells in case 1 contained glycogen or lipid-distended cytoplasm with a foamy appearance (low grade), and in cases 2, 3, and 4, they displayed a similar morphology characterized by epithelioid cells with eosinophilic and granular cytoplasm and high-grade nuclear atypia. Different from the LMS component, the epithelioid PEComa cells in all cases were focally positive for HMB-45, and diffusely immunoreactive for cathepsin K and GPNMB. Melan A was focally positive in cases 1 and 3. Loss of fumarate hydratase expression (case 1) and RB1 expression (cases 2, 3, 4) was identified in both LMS and PEComa components, indicating that they are clonally related. In addition, both components showed an identical TP53 p.R196* somatic mutation and complete loss of p53 and ATRX expression in case 2 and complete loss of p53 expression in case 3. We hypothesize that LMSs containing smooth muscle progenitor cells may give rise to divergent, lineage-specific PEComatous lesions through differentiation or dedifferentiation. While we do not dispute the recognition of PEComas as a distinct entity, we advocate the hypothesis that modified smooth muscle cells represent the origin of a subset of PEComas, and our case series provides evidence to suggest this theory.

A case of pancreatic PEComa with prominent inflammatory cell infiltration: the inflammatory subtype is a distinct histologic group of PEComa

BACKGROUND

PEComa is a mesenchymal tumor that can occur in various organs including the uterus and soft tissues. PEComas are composed of perivascular epithelioid cells, and angiomyolipoma (AML), clear cell sugar tumor (CCST), and lymphangiomyomatosis (LAM) are considered lesions of the same lineage as tumors of the PEComa family. Histologically, a common PEComa shows solid or sheet-like proliferation of epithelioid cells. This is accompanied by an increase in the number of dilated blood vessels. Here, we report a case of pancreatic PEComa with marked inflammatory cell infiltration.

CASE PRESENTATION

A 74-year-old male patient underwent an appendectomy for acute appendicitis. Postoperative computed tomography and magnetic resonance imaging revealed a 30 × 25 mm non-contrast-enhanced circular lesion in the tail of the pancreas. The imaging findings were consistent with a malignant tumor, and distal pancreatectomy was performed. Histologically, most area of the lesion was infiltrated with inflammatory cells. A few epithelioid cells with large, round nuclei, distinct nucleoli, and eosinophilic granular cytoplasm were observed. Spindle-shaped tumor cells were observed. Delicate and dilated blood vessels were observed around the tumor cells. Immunohistochemically, the atypical cells were positive for αSMA, Melan A, HMB-45, and TFE3. The cytological characteristics of the tumor cells and the results of immunohistochemical staining led to a diagnosis of pancreatic PEComa.

CONCLUSIONS

A histological variant known as the inflammatory subtype has been defined for hepatic AML. A small number of tumor cells present with marked inflammatory cell infiltration, accounting for more than half of the lesions, and an inflammatory myofibroblastic tumor-like appearance. To our knowledge, this is the first report of pancreatic PEComa with severe inflammation. PEComa is also a generic term for tumors derived from perivascular epithelioid cells, such as AML, CCST, and LAM. Thus, this case is considered an inflammatory subtype of PEComa. It has a distinctive morphology that is not typical of PEComa. This histological phenotype should be widely recognized.

A Case Report of Malignant Perivascular Epithelioid Cell Tumors of the Uterus and Literature Review

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal tumors originating from perivascular epithelioid cells. In gynecological system, the uterus is one of the most common sites affected by PEComas. Most PEComas are benign, and patients usually have a good prognosis. However, malignant uterus PEComa is rare, and better comprehensive epidemiological investigations are needed. To date, there are a few reported cases of uterus PEComa. We herein report a rare case of malignant PEComa occurred in the uterine corpus and cervix, possibly accompanied by pulmonary lymphangioleiomyomatosis (PLAM). In addition, 55 cases of malignant uterus PEComa were picked out and collected in the data base of PubMed and Medline. On the one hand, the age of onset, population distribution, clinical manifestations, metastatic sites and routes of metastasis were analysed. On the other hand, a summary of the epidemiology, pathogenesis, diagnosis, and treatments of uterus PEComa was given.

Case report: Urachal perivascular epithelioid cell tumor

Background

Urachal tumors are rare in clinical practice, among which urachal adenocarcinoma is the most common. In this study, we report a rare case of urachal perivascular epithelioid cell tumor to improve our understanding of the disease.

Case presentation

A 26-year-old male patient was hospitalized for lower abdominal pain. The US showed a hypoechoic mass measuring 26mm × 18mm in the superior aspect of the bladder. MRI showed an irregular mass located anterior to the bladder roof, near the midline. The tumor exhibited hypointense on T1WI and heterogeneous hyperintense on T2WI. Additionally, contrast-enhanced T1-weighted imaging revealed obvious ring enhancement of the tumor. The patient underwent surgical resection of the urachal tumor, with subsequent pathological examination revealing a diagnosis of urachal PEComa. Following surgery, the patient underwent regular follow-up assessments, with no evidence of recurrence or metastasis observed after three and a half years.

Conclusions

Urachal PEComa is a rare mesenchymal tumor that presents challenges in diagnosis through imaging and clinical symptoms. Definitive diagnosis relies on pathological and immunohistochemical analysis. Due to the rarity of urachal PEComa, prognosis assessment necessitates long-term follow-up and evaluation of more cases.

Soft Tissue Perivascular Epithelioid Cell Tumors

Perivascular epithelioid cell tumors (PEComas) are a heterogenous group of mesenchymal neoplasms with a mixed myomelanocytic immunophenotype. PEComa-family tumors include angiomyolipoma, lymphangioleiomyomatosis, and a large category of rare neoplasms throughout the body that are now classified under the umbrella term "PEComa." This review focuses on recent advances in the clinicopathological and molecular features of PEComas, with an emphasis on PEComas that originate in soft tissue.

Hepatic Angiomyolipoma With Predominant Lipomatous Component: A Rare Entity

Hepatic angiomyolipoma (HAML) is a rare benign mesenchymal tumor with varying amounts of mature adipose tissue, smooth muscle cells, and thick-walled blood vessels. We present a rare case of hepatic angiomyolipoma (AML) with predominant lipomatous components. A 42-year-old female presented to the hospital with pain in the right lumbar region. On imaging, there was a large fat-predominant mass attached to the surface of the liver extending down to the lumbar region. On small biopsy, it was reported as a well-differentiated adipocytic neoplasm, and fluorescence in situ hybridization (FISH) studies performed for MDM2 were negative. On excision, histopathological examination showed predominantly fat components, but there were few epithelioid cells between adipocytes and thick-walled blood vessels. These cells were positive for Melan-A, HMB45, and smooth muscle actin (SMA) and negative for hepatocyte paraffin-1 (Hep Par1). Angiomyolipoma is a benign tumor and has a good prognosis with surgical excision. Few cases are associated with tuberous sclerosis.

Hepatic perivascular epithelioid cell tumor resembling hepatic adenoma and hepatocellular carcinoma on preoperative imaging: a case report

Perivascular epithelioid cell tumor (PEComa), an uncommon mesenchymal neoplasm, arises from specialized perivascular epithelioid cells exhibiting distinct features of smooth muscle and melanocytic differentiation with unpredictable behavior. PEComa tends to occur more commonly in the uterus and kidneys; its occurrence in the liver is exceedingly rare. We presented a case of a 29-year-old woman with hepatic PEComa and evaluated the tumor with MRI, integrated 18F-fluorodeoxyglucose (FDG), and 68Ga-fibroblast activation protein inhibitor (FAPI) PET/CT scans at presentation. The patient had a history of intermittent utilization of oral contraceptive drugs for several years. An abdominal ultrasound in a physical examination from an outside institution revealed a mass in the liver. A contrast-enhanced abdominal MRI revealed restricted diffusion on diffusion-weighted imaging (DWI) and rapid contrast enhancement and washout patterns in the hepatic lesion, suggesting hepatic adenoma (HA) or hepatocellular carcinoma (HCC). Further assessment was carried out using 18F-FDG and 68Ga-FAPI PET/CT scans. The hepatic lesion was non-FDG avid, whereas increased tracer uptake was observed on the 68Ga-FAPI PET/CT. Subsequently, laparoscopic partial resection of liver segment V was performed. Immunohistochemical analyses demonstrated positive staining for HMB45, Melan-A, and SMA while showing negative results for AFP, glypican-3, hepatocyte, and arginase-1. The results were indicative of a hepatic PEComa diagnosis based on these findings. We also review the current literature on the clinical characteristics, pathological features, and challenges in the diagnosis of hepatic PEComa.

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.

Bladder perivascular epithelioid cell neoplasm: Review on clinical features of this rare tumor

Perivascular epithelioid cell neoplasm (PEComa) is a rare mesenchymal tumor composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. They can arise in various localizations such as the bladder. A total of 36 case reports regarding bladder PEComa have been described in the literature. Eleven reviews regarding this tumor have been published in literature so far primarily focusing on anatomic pathology. Through these reviews, it is known that in bladder PEComa, the melanocytic marker Human Melanoma Black-45 is expressed in 100% of cases whereas variable expression can be seen in multiple other melanocytic and myoid markers such as smooth muscle actin, Melan-A, CD117, S100, CD31, and CD34. Since current reviews mainly emphasize anatomic pathology, we perform a review focusing on the clinical aspects of PEComa at the level of the clinician. A manual electronic search of the PubMed/Medline and Web of Science Core Collection databases was conducted. Search was done on (perivascular epithelioid cell neoplasms [MeSH terms]) AND (Bladder). All case reports and reviews were encompassed until March 15, 2023, to identify studies that assessed bladder PEComa. The age of presentation is relatively low with a median age of 37 years. There is a female predominance with a female/male ratio of 1.5. The tumor shows no preference in anatomical localization within the bladder. Even involvement of the bladder neck, proximal urethra, and distal ureter has been described. The clinical presentation consists in the majority of patients of symptoms related to the urinary tract such as hematuria, dysuria, passage of urine sediment, frequency, and urgency. Other symptoms include abdominal discomfort and dysmenorrhea. In clinical examination, an abdominal mass can be found based on the size and location of the tumor. Further examination usually encompasses cystoscopy due to the hematuria and radiological investigations such as ultrasound (US), computed tomography, and magnetic resonance imaging. These radiological investigations reveal a heterogeneous solid mass with clear borders. In our center, we performed a transvaginal US additionally in a patient with bladder PEComa, which was the only investigation in our patient that concluded the mass was located in the Retzius space. For treatment, transurethral resection of the bladder tumor and partial cystectomy were both described in equal numbers. The choice of treatment depends on the localization and size of the tumor. Follow-up consists of imaging, but clear guidelines on this matter are lacking. Bladder PEComa is a rare condition and usually presents itself with nonspecific symptoms. Radiological investigations will reveal the tumor, but the final diagnosis is based on cytological and immunohistochemical features. Since bladder PEComa is an entity with uncertain malignant potential, it is important to include this entity in the differential diagnosis when a patient presents with lower abdominal discomfort and lower urinary tract symptoms in combination with a mass in the pelvic region.

Perivascular epithelioid cell tumors (PEComas) of the bone and soft tissue: a Japanese Musculoskeletal Oncology Group (JMOG) multi-institutional study

PURPOSE

Perivascular epithelioid cell tumors (PEComas) of the bone and soft tissues are rare mesenchymal neoplasms, some of which are malignant. However, their clinical and pathological characteristics remain unclear. This study was performed to investigate the clinical and pathological characteristics of PEComas in bone and soft tissues by leveraging information from the Japanese Musculoskeletal Oncology Group.

METHODS

Nine patients, including four male and five female patients with a median age of 50 years, were retrospectively reviewed. PEComas of the visceral organs, including the uterus and retroperitoneum, were excluded.

RESULTS

Eight tumors arose in the soft tissue and one in the bone, with a mean size of 8.8 cm. Four patients showed local recurrence or distant metastasis. The 1-year survival rate was 78%. Pathologically, eight tumors were classified as malignant and one as having uncertain malignancy potential. Half of the tumors showed high MIB-1 index values of > 30%. Immunohistochemically, the melanocyte marker HMB45 was expressed in 89% of the cases, and muscle-specific markers were expressed only in 30-50% of the cases. Transcription factor binding to IGHM enhancer 3 (TFE3) expression was positive in 100% of the patients. Tumors with high expression of TFE3 were classified as PEComas with malignant potential according to Folpe's classification.

CONCLUSIONS

Bone and soft tissue PEComas may have a higher malignancy potential than other visceral PEComas and are more likely to develop as TFE3-rearranged PEComas.

Mesenchymal Neoplasms of the Liver

Mesenchymal neoplasms of the liver can be diagnostically challenging, particularly on core needle biopsies. Here, I discuss recent updates in neoplasms that are specific to the liver (mesenchymal hamartoma, undifferentiated embryonal sarcoma, calcifying nested stromal-epithelial tumor), vascular tumors of the liver (anastomosing hemangioma, hepatic small vessel neoplasm, epithelioid hemangioendothelioma, angiosarcoma), and other tumor types that can occur primarily in the liver (PEComa/angiomyolipoma, inflammatory pseudotumor-like follicular dendritic cell sarcoma, EBV-associated smooth muscle tumor, inflammatory myofibroblastic tumor, malignant rhabdoid tumor). Lastly, I discuss metastatic sarcomas to the liver, as well as pitfalls presented by metastatic melanoma and sarcomatoid carcinoma.

Malignant Perivascular Epithelioid Cell Neoplasm of Left Kidney Treated With Targeted Therapy: A Rare Case Report

Perivascular epithelioid cell neoplasm (PEComa) is one of the rare entities which is challenging to diagnose clinically. These tumors occur due to tuberous sclerosis complex gene mutations leading to upregulation and overexpression of the mammalian target of rapamycin (mTOR). Malignant PEComas are rare, and we report a peculiar case of PEComa treated with mTOR inhibitors. A 43-year-old woman presented with complaints of back pain, intermittent fever, dysuria, and cough with expectoration for one month. Abdominal computed tomography (CT) revealed heterogeneously enhancing exophytic mass of the left kidney. A positron emission tomography CT whole body showed a primary malignancy in the left kidney, sclerotic lesions in the bony skeleton, and lymphangitis carcinomatosis in both lungs. A biopsy of the left renal mass revealed PEComa, focally positive for melanocytic and muscle markers. She was commenced on treatment with intravenous temsirolimus, and there was a complete tumor regression by the end of the completion of six cycles.

Systemic Treatments and Molecular Biomarkers for Perivascular Epithelioid Cell Tumors: A Single-institution Retrospective Analysis

Perivascular epithelioid cell tumors (PEComa) are a large family of mesenchymal neoplasms, with variable clinical course. Evidence regarding treatment of advanced PEComas is scarce, with only one FDA-approved treatment available. The goals of this study were to provide data regarding systemic treatments for advanced PEComas and to identify biomarkers of prognostic relevance. This is a single-institution retrospective study of patients with advanced PEComas requiring systemic treatment, including malignant PEComa, angiomyolipoma (including the epithelioid variant), and lymphangioleiomyomatosis. Outcomes measured were overall survival (OS), first-line and combined progression-free survival (PFS), and tumor response. Kaplan-Meier, univariable, and multivariable Cox proportional hazards analysis were performed. A total of 29 patients were included, most with malignant PEComa (n = 17). Median OS was 204.9 months, while median PFS was 92.4 months from first-line, and 15.8 months for all lines combined. TFE3 overexpression correlated with higher risk of death (HR: 11.8, P = 0.04), and shorter median OS (P = 0.001). Chemotherapy and mTOR inhibitors showed similar OS (P = 0.84), and first-line PFS (P = 0.67). Combined PFS was similar between individual mTOR inhibitors, chemotherapy, immune checkpoint inhibitors and other treatments (P = 0.19). Different mTOR inhibitors demonstrated similar efficacy, making cost and availability important considerations when choosing a specific agent. mTOR inhibitors showed similar outcomes as chemotherapy, suggesting that these should be preferred whenever possible for patients with PEComas given the morbidity associated with chemotherapy. TFE3 overexpression highlighted a subgroup of PEComas with worse prognosis and more aggressive behavior.

Significance

This study examines systemic treatments for advanced PEComas, a rare group of sarcomas, and identifies molecular biomarkers of prognosis. Our results show that mTOR inhibitors have similar efficacy as chemotherapy, and that TFE3 overexpression, on IHC or FISH, correlates with a more aggressive disease course.

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

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

A Clinicopathologic and Molecular Characterization of Uterine Sarcomas Classified as Malignant PEComa

Perivascular epithelioid cell tumors (PEComas) are a distinctive group of mesenchymal neoplasms that demonstrate features of smooth muscle and melanocytic differentiation. Here, we present the clinicopathologic, immunohistochemical, and molecular features of 15 uterine sarcomas diagnosed as malignant PEComa. The median patient age was 56 years (range: 27 to 86 y). The median tumor size was 8.0 cm (range: 5.0 to 14.0 cm). All tumors were classified as malignant based on the presence of mitoses (15/15; 100%), necrosis (15/15; 100%), lymphovascular invasion (8/15; 53%), and high nuclear grade (13/15; 87%). Molecular analysis revealed the mammalian target of rapamycin pathway gene mutations in 7 cases (47%), including mutually exclusive variants in TSC1 (27%) and TSC2 (20%). Recurrent alterations were also identified in TP53 (53%), RB1 (30%), ATRX (33%), and BRCA2 (13%). Tumors with inactivating ATRX mutations all demonstrated loss of ATRX expression by immunohistochemistry. Loss of expression was also observed in 2 tumors without demonstrable ATRX alterations. Clinical follow-up was available for 14 patients (range: 5 to 92 mo; median: 15 mo). Five patients developed local recurrence and 9 developed metastases; 2 patients died of their disease. Our series expands the spectrum of molecular events in tumors diagnosed as malignant PEComa and further highlights the important role of targeted sequencing in tumors with focal melanocytic marker expression.

Clear cell "sugar" tumor of the lung: Diagnostic characteristics of a rare pulmonary tumor: A case report and review of literature

INTRODUCTION

Clear cell tumors of the lung (CCTLs), also known as "sugar tumors" for an abundant cellular glycogen concentration, are an extremely rare type pulmonary neoplasm. Often, they are incidentally found on chest roentgenogram or computed tomography scan during routine examination. CCTLs usually present with nonspecific symptoms that pose a diagnostic challenge to clinicians. Accordingly, histopathology remains the gold standard for diagnosing. Moreover, some of them can present with either appearances or histopathological features similar to other pulmonary neoplasms under the light microscope, including pulmonary malignancy, thereby causing misdiagnosis prior to or after surgery. Accordingly, herein, we describe a rare case of CCTL, review the literature has been published, and then discuss the benign versus malignant nature of this rare tumor.

PATIENT CONCERNS

A 59-year-old man presented due to a high-density chest nodule in the left diaphragm. The patient's medical history was unremarkable and he also denied smoking in the past.

DIAGNOSIS

Physical examination, there were no noted signs. A new chest contrast-enhanced computed tomography revealed a 3.2 × 2.5 cm, solitary, circular nodule with a smooth edge located in the beside of the left thoracic aorta. Postoperative pathological and immunohistochemical examinations of the surgical specimens revealed a final diagnosis of CCTLs.

INTERVENTIONS

The patient underwent video-assisted thoracoscopic surgery. A wedge resection of left lower lung lobe was carried out and the tumor node was successfully removed alongside normal surrounding parenchyma.

OUTCOMES

The operation was successful. Then the patient recovered completely and continued to do well on postsurgical thoracic surgical clinic visits. The tumor was a benign tumor, and the patient did not require any additional treatment. The patient had been followed-up regularly for 4 years after surgery; she did not experience any complications and remained disease-free.

CONCLUSION

CCTLs should be considered in the differential diagnosis if a patient shows a solitary, circular chest nodule with a smooth edge. They are extremely rare lung tumors that must be differentiated from other lung tumors, especially the malignant tumors. Although pathological and immunohistochemical findings are important for making the diagnosis, the varying histopathological features on microscope make diagnosis difficult. The current case highlights the importance of physicians being aware of and suspecting CCTLs in similar cases, along with knowing the characteristics of CCTLs for the diagnosis and differential diagnosis.

Perivascular Epithelioid Cell Tumor (PEComa) of the Pancreas in a Patient with Ulcerative Colitis: A Case Report and Review of the Literature

Perivascular epithelioid cell tumors (PEComas) are mesenchymal tumors of peculiar cells that are focally associated with blood vessels, and generally have a distinctive bi-phenotypic expression of both smooth muscle and melanocytic markers. There are several entities in the PEComa family, including tumors that arise in the soft tissues and viscera. Frequently affected organs include the lungs (sugar tumors), uterus, broad ligament, colon, small bowel, liver, and pancreas. Ulcerative colitis (UC) has been associated with the development of tumors, especially colorectal and hepatobiliary carcinomas. Rare cases of UC have been reported in the PEComa family of tumors, but none in the pancreas. Here, we present a case study of a 27-year-old female patient with a history of UC who developed PEComa of the pancreas, a unique association that has not been previously reported. We also review reported cases of PEComas in the pancreas, as well as PEComas at all anatomic sites associated with UC.

Malignant retroperitoneal PEComa: A case report with emphasis on radiological findings

A perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm with distinctive perivascular epithelioid cells that usually demonstrates myomelanocytic differentiation. PEComas can arise in various organs and generally are benign. Uncommonly PEComas have been documented to be malignant with metastasis most frequently to the lung, liver, lymph nodes, and bone. Here, we present the case of a 59-year-old male with a malignant retroperitoneal PEComa with confirmed metastasis to the femur and suspected metastasis to the liver and lung. The purpose of this case study is to present the progression and findings of a metastatic malignant PEComa.

Case Report: Perivascular epithelioid tumors of the gastrointestinal tract

Background

Perivascular epithelioid cell tumor of the gastrointestinal tract (GI PEComa) is a rare mesenchymal neoplasm. GI PEComa is mostly observed in the colon and has a marked middle-aged female predominance. PEComa has no typical clinical or imaging manifestations or endoscopic characteristics. Therefore, the diagnosis of this disease mostly relies on pathological findings. HMB-45 is a sensitive immune marker of PEComa.

Case presentation

We reported a case of a middle-aged female with sigmoid colon PEComa. To exclude carcinogenesis, the large basal polyp in the sigmoid colon was removed by endoscopic mucosal resection (EMR). Immunohistochemistry analysis results showed that this lesion expressed HMB-45, which is a characteristic melanin marker of PEComa. Finally, the lesion was diagnosed as sigmoid colon PEComa. At the time of submission of this report, surgical resection was the primary treatment for PEComa. Though the characteristics of tumor biology and clinical behavior in PEComa are not clear, the boundary is clear, and the tumor can be completely removed. However, close follow-up is required after the surgery because of the lesion's undetermined benign and malignant nature.

Conclusion

The present case study emphasizes the importance of pathological diagnosis. Therefore, upon finding gastrointestinal polyps with a mucosal ulcer under endoscopy, the GI PEComa diagnosis should be considered. It is necessary to detect the characteristic melanin markers of PEComa. Due to the rarity of these cases, challenges are faced in diagnosing and treating PEComa.

Metastatic Adrenal PEComa: Case Report and Short Review of the Literature

PEComa has become a widely accepted entity, and increased recognition has led to descriptions of this tumor in a wide variety of anatomic sites, including the adrenal gland. PEComa (perivascular epithelioid cell tumor) is a mesenchymal tumor composed of perivascular cells, and the most frequent sites of PEComas are the uterus and retroperitoneum. The incidence is <1 per 1,000,000 people. We report a case of adrenal metastatic PEComa in a 63-year-old man discovered by a spontaneous hematoma of the rectus abdominis. In our case, PEComa of the adrenal gland was a significant diagnostic dilemma as the morphologic and immunophenotypic features of this neoplasm may easily be confused with those of other more commonly encountered lesions.

Basics, Epidemiology, Diagnosis, and Management of Liver Tumor

Liver tumors include both benign (non-cancerous) and malignant (cancerous) varieties [...].

Specific imaging features indicate the clinical features of patients with hepatic perivascular epithelioid cell tumor by comparative analysis of CT and ultrasound imaging

Objective

The objective of the study was to explore the CT and ultrasound features and clinical significance of perivascular epithelioid cell tumor (PEComa) of the liver.

Methods

Eleven hepatic PEComa patients treated in our hospital were retrospectively analyzed based on the characteristics of the imaging results of the patients, including conventional ultrasound, CDFI, contrast-enhanced ultrasound (CEUS), and contrast-enhanced CT (CECT).

Results

CT scans showed that all lesions were hypodense. Ultrasonography showed that lesions were either hyperechoic (4/11, 36.36%), hypoechoic (4/11, 36.36%), isoechoic (1/11, 9.09%), or heterogeneously echoic (2/11, 18.18%). CDFI showed that most of the lesions had an abundant blood supply (9/11, 81.82%). Whether on CT scan or ultrasonography, the margins of the lesions were dominated by clear margins. Ultrasonography revealed more features: hyperechoic patterns around lesions (3/11, 27.27%) and lateral shadow (5/11, 45.45%). The CDFI showed that large blood vessels were observed around the lesions (9/11, 81.82%). CECT shows two enhancement patterns: “fast in and fast out (FIFO)” (8/11, 72.72%) and “fast in and slow out (FISO)” (3/11, 27.27%). CEUS shows that all lesions had the enhancement pattern of “FISO,” which was different from CECT. All lesions displayed rapid enhancement during HAP in CEUS during 7–20 s. Four patients (36.36%) washed out at 60–180 s, another four (36.36%) washed out at 180–300 s, and the remaining three patients (27.27%) showed no signs of washout even at 360 s.

Conclusion

Some imaging features, such as clear margins, peripheral hyperechoic around the lesion, lateral shadow, the large blood vessels around lesions, and the “FISO” enhancement pattern, may indicate expansive growth of the tumor and be helpful in the diagnosis of PEComa. Ultrasound images may provide more details for clinical reference.

Sclerosing Perivascular Epithelioid Cell Tumor of the Uterus: A Rare Entity Posing Diagnostic Challenge

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal uterine tumor and the histological variant, sclerosing PEComa is exceedingly rare. Sclerosing PEComas preferentially occur in the retroperitoneum and occurrence in the uterine corpus is seldom seen. These tumors pose a diagnostic challenge and need distinction from morphological mimickers such as epithelioid smooth muscle tumors, endometrial stromal sarcoma, and metastatic carcinoma. Accurate diagnosis can be established coupling histomorphology with immunostaining. The distinction from other entities is of prime importance considering the therapeutic and prognostic implications. Herein, we describe a case of uterine sclerosing variant of PEComa with diagnostic difficulties and key to diagnose this entity.

Cutaneous Angiomyolipoma-A Distinct Entity That Should Be Separated From Classic Angiomyolipoma: Complete Review of Existing Cases and Defining Fundamental Features

Cutaneous angiomyolipoma is a rare mesenchymal tumor that is demographically, clinically, and immunohistochemically distinct from its renal and extrarenal counterparts. We present a case of cutaneous angiomyolipoma in the right retroauricular area of a 35-year-old male patient and provide a broad systematic review of the literature and the largest compilation of cutaneous angiomyolipomas reported to date. According to the findings presented in this review, we conclude that cutaneous angiomyolipoma should be completely separated from renal and extrarenal angiomyolipomas and therefore be considered a distinct entity in the classification of skin tumors.

Unique presentation of retroperitoneal malignant perivascular epithelioid cell tumor (PEComa) in a young male

Perivascular Epithelioid Cell tumors (PEComas) are rare mesenchymal tumors composed of epithelioid and spindle cells that can be found almost anywhere in the body with predominance for abdominopelvic locations. They are usually diagnosed in middle-aged females and are associated with tuberous sclerosis complex. This report describes an unusual presentation of a malignant retroperitoneal PEComa in an otherwise healthy, young male. Treatment included radical nephrectomy and adrenalectomy followed by medical oncology evaluation.

A unique case of abdominal pain and anemia

A 38-year-old female presented with intermittent abdominal pain and rectal bleeding and found to have severe anemia. The computerized tomography of abdomen and pelvis with contrast showed a solid mass measuring 5.4 × 3.4 × 3.1 cm in the cecum (Figure 1, left). The colonoscopy revealed a large protruding lesion with ulceration in the right colon (Figure 1,right). Multiple biopsies of the ulcerated area were obtained.

Giant hepatic angiomyolipoma presenting with severe anemia: A surgical case report and review of literature

Background

Angiomyolipoma (AML) is a solid benign neoplasm with mesenchymal features. The clinical signs and symptoms of hepatic angiomyolipoma are nonspecific, and treatment strategy is variable.

Presentation

A 35-years-old male patient has admitted to the hospital with symptoms of severe anemia. Abdominal multi-slice computed tomography (MSCT) and Gadoxetic acid (GA)-enhanced magnetic resonance imaging (MRI) revealed a heterogeneous 23 × 17 cm-in-sized tumor with heterogeneous enhancement and increased angiogenesis. Percutaneous hepatic biopsy was proceeded and in immunohistochemistry, tumor cells responded positively to the HMB-45, SMA, and Glutamine stains, the CD-34 stain was positive for blood vessels as well as Ki-67 sporadically positive, but the Heppar1, S-100, CK stains reacted negative. The final pathologic result was consistent with the primary hepatic angiomyolipoma. The final surgical management was extended right hepatectomy with ligation of the right hepatic artery (RHA) and vein (RHV), as well as the middle hepatic vein (MHV), one month after portal embolization as well as to enlarge the remnant liver volume.

Discussion

A hepatic angiomyolipoma (HAML) primary origin is relatively rare, the clinical manifestations are variable and non-specific. Histological examination and immunohistochemistry staining are considered as the gold standard for HAML diagnosis. HAML are commonly expressed benign behaviors, but HAML cases with malignant behaviors were reported in a cumulative incidence. Radical surgery must be still the most effective and major treatment approach.

Conclusion

The present case being the first case with initial syndrome of severe anemia accounted in the English literature. Giant angiomyolipoma is composed of blood vessels and could lead to extensive internal tumoral hemorrhage. We here present a report of this case with had primary hepatic angiomyolipoma with clinical picture of severe anemia.

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A hepatic angiomyolipoma (HAML) is occasionally rare, the clinical manifestations are variable and non-specific.

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Histological examination and immunohistochemistry staining are considered as the gold standard.

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Radical surgery is the most effective and major treatment approach for symptomatic or big-sized HAML.

Nevus, melanoma or something else? Mesenchymal neoplasms with melanocytic differentiation

The overwhelming majority of cutaneous neoplasms with melanocytic differentiation are nevi, melanomas and more rarely melanocytomas. Nevertheless, there is also a group of mesenchymal neoplasms with genuine melanocytic differentiation which can create diagnostic difficulties with significant repercussions. These can rarely present as primary or metastatic cutaneous lesions. Theones that are relevant to a dermatopathologist include malignant melanotic nerve sheath tumor, perivascular epithelioid cell neoplasm and clear cell sarcoma. This work will provide a thorough review of clinical presentation, morphologic and immunohistochemical features as well as molecular pathogenesis of these tumors. We hope to familiarize the general dermatopathology readership with a group of neoplasms of mesenchymal lineage exhibiting melanocytic differentiation and ultimately avoid diagnostic misadventures. This article is protected by copyright. All rights reserved.

Single-center Experience in the Diagnosis and Treatment of Hepatic Perivascular Epithelioid Cell Neoplasm

BACKGROUND AND AIMS

Perivascular epithelioid cell neoplasms (PEComas) are a rare type of mesenchymal neoplasm and their preoperative diagnosis is challenging. In this study, we summarized the experience from a single medical center to study the examinations, clinical presentations, and pathological and histological characteristics of PEComas in the liver in order to optimize overall understanding of the diagnosis and treatment of these neoplasms.

METHODS

We conducted a retrospective analysis to investigate the clinical and pathological characteristics as well as imaging presentations of 75 patients diagnosed with hepatic PEComa in The First Affiliated Hospital of Zhejiang University between April 2010 and April 2020.

RESULTS

Among the 75 patients, 52 were women, and the median age was 48 years. Most patients had no specific symptoms, and two were admitted to the hospital for a second time owing to relapse. All patients underwent surgical resection. Histologically, 38 patients had classical angiomyolipoma (AML) and 37 had epithelioid AML. The PEComas were accompanied by positive immunohistochemical expression of HMB45, Melan-A, and smooth muscle actin. Follow-up data were obtained from 47 of the total 75 patients, through October 2020. Two patients had metastasis after surgery.

CONCLUSIONS

AML is the most common type of hepatic PEComa. There are no specific symptoms of hepatic PEComa, and serological examinations and imaging modalities for accurate preoperative diagnosis are lacking. Epithelioid AML should be considered a tumor of uncertain malignant potential; however, the prognosis of PEComa after resection is promising.

Perivascular epithelioid cell tumour (PEComa): an unusual cause of painful defaecation

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.

Natural History and Treatment Strategies of Advanced PEComas: A Systematic Review

Simple Summary

In this article, we review the clinical features of advanced PEComas and show the diversity of reported data among authors, emphasizing the heterogeneity of molecular characterization and treatment strategy. Based on clinical data collected from 124 case reports, metastatic disease at diagnosis and a grouped version of the Bleeker’s risk category were the only factors significantly associated with death. Due to a significant number of missing data or short follow-ups, results regarding prognostic factors should, however, be interpreted with caution.

Abstract

PEComas is a family of rare mesenchymal tumors. This systematic review aims to better understand the natural history of advanced PEComas. After a search on the PubMed database and main oncology meeting libraries according to the PRISMA guidelines, 88 articles reported in the English literature were included. Data on clinical and histological features, treatments and outcomes were collected. To identify risk factors, univariate and multivariate analyses were performed. Seven cohorts of patients and 124 individual patients were identified. Focusing on case reports, most patients were metastatic, and the median overall survival (OS) of the entire cohort was 60 months (95%CI 33; NA). Risk factors significantly associated with OS in the multivariate analysis were the presence of metastasis at diagnosis (HR: 2.59, 95%CI 1.06; 6.33, p = 0.036) and the grouped-Bleeker’s risk category (HR: 4.66; 95%CI 1.07; 20.19; p = 0.039). In the metastatic population, only the presence of lymph node metastasis was associated with OS (HR: 3.11; 95%CI 1.13; 8.60, p < 0.05). Due to a lack of events, it was not possible to conclude on other factors. This review of the literature highlights the heterogeneity of literature data and shows the great diversity of clinical management strategies.

Hepatic perivascular epithelioid cell tumor: Clinicopathological analysis of 26 cases with emphasis on disease management and prognosis

BACKGROUND

Perivascular epithelioid cell tumor (PEComa) is an uncommon tumor of mesenchymal origin. Cases of PEComa in the liver are extremely rare.

AIM

To analyze the clinicopathological features and treatment of hepatic PEComa and to evaluate the prognosis after different treatments.

METHODS

Clinical and pathological data of 26 patients with hepatic PEComa were collected. All cases were analyzed by immunohistochemistry and clinical follow-up.

RESULTS

This study included 17 females and 9 males, with a median age of 50 years. Lesions were located in the left hepatic lobe in 13 cases, in the right lobe in 11, and in the caudate lobe in 2. The median tumor diameter was 6.5 cm. Light microscopy revealed that the tumor cells were mainly composed of epithelioid cells. The cytoplasm contained heterogeneous eosinophilic granules. There were thick-walled blood vessels, around which tumor cells were radially arranged. Immunohistochemical analysis of pigment-derived and myogenic markers in PEComas revealed that 25 cases were HMB45 (+), 23 were Melan-A (+), and 22 SMA (+). TFE3 and Desmin were negative in all cases. All the fluorescence in situ hybridization samples were negative for TFE3 gene break-apart probe. Tumor tissues were collected by extended hepatic lobe resection or simple hepatic tumor resection as the main treatments. Median follow-up was 62.5 mo. None of the patients had metastasis or recurrence, and there were no deaths due to the disease.

CONCLUSION

Hepatic PEComa highly expresses melanin and smooth muscle markers, and generally exhibits an inert biological behavior. The prognosis after extended hepatic lobe resection and simple hepatic tumor resection is semblable.

Primary soft tissue angiomyolipoma in a dog with unusual clinical features

Angiomyolipoma is an extremely rare neoplasm in animals. It belongs to a group of perivascular epithelioid cell tumours (so-called PEComas). This study reports a case of primary soft tissue angiomyolipoma in a dog with some unusual clinical features. A 4-year old female Labrador dog with a rapidly growing pelvic tumour measuring 30 × 20 cm with a short history of 12 weeks was presented. The tumour was well-circumscribed and pushed into the right vaginal wall and into the perineum. The tumour was completely surgically excised. An extensive histological examination was performed, including immunohistochemical analysis. Histology revealed a mesenchymal neoplasm consisting of three tissue components – mature adipose tissue (which dominated), vessels, and smooth muscle (spindle) cells. The lesion showed positive immunohistochemical staining with smooth muscle actin and desmin in mature-appearing smooth muscle cells and S-100 protein positivity in adipocytes. The diagnosis of angiomyolipoma must be considered in different types of benign and malignant tumours of various lineages. The diagnostic approach to soft tissue tumours, including angiomyolipoma, requires optimal processing and sectioning of resected specimens. This paper is believed to be the first case of primary soft tissue angiomyolipoma reported in the veterinary literature.

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.

Retroperitoneal Sclerosing Angiomyolipoma with Long-Term Follow up: A Case Report with Unique Clinicopathologic and Genomic Profile

Sclerosing angiomyolipoma (sAML) is a rare variant of the perivascular epithelioid tumors exhibiting distinct morphology with extensive stromal hyalinization, which makes it challenging to recognize. It often lacks an adipose tissue component and melanocytic markers may be expressed only focally, further posing a diagnostic challenge. Here, we report a case of sAML of the left pararenal retroperitoneum in a 52-year-old woman with 92 months of clinical follow up and discuss the histologic features, immunoprofile, molecular alterations, and differential diagnoses that can aid in the diagnosis of this unique and rare entity.

Uterine PEComa initially misdiagnosed as a leiomyoma: Sonographic findings and review of the literature

Perivascular epithelioid cell neoplasms (PEComas) are rare mesenchymal tumors with malignant potential that arise from gynecological organs in up to 25% of cases. The lack of data regarding the preoperative US features of uterine PEComas is reflected by the frequent misdiagnosis with leiomyomas. We describe the sonographic appearance of a richly vascularized cervical PEComa mimicking a myoma and report the analysis of six additional cases in the literature with a description of their ultrasound features. Most cases involved a single lesion arising from the uterine cervix with a rapid growth pattern, regular margins, heterogeneous echogenicity, absence of shadowing, and moderate-to-rich vascularity.

Bladder perivascular epithelioid cell tumour and tuberous sclerosis complex: a rare association

Bladder perivascular epithelioid cell tumours (PEComas) associated with tuberous sclerosis complex (TSC) are rare, with only one other case report in the literature to date. We present our case of a bladder PEComa in a young adult female with TSC arising de novo. Histopathology showed features in keeping with an angiomyolipoma and confirmatory immunohistochemical stains were positive for both melanocytic and smooth muscle markers. She was well at the 6-month follow-up post-surgical resection. Given the rarity of such lesions in the bladder, we discuss the diagnostic and prognostic challenges, clinical implications and a brief review of the literature to date.

Perivascular Epithelioid Cell Tumor of the Buttock Region

Perivascular epithelioid cell neoplasms, also known as PEComas, are a group of rare mesenchymal tumors that have a perivascular distribution and have no known counterpart to normal cells. The PEComa grouping includes angiomyolipomas, lymphangioleiomyomatoses, clear cell (sugar) tumors at extrapulmonary and intrapulmonary sites, clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres among others. These rare tumors most commonly arise in the uterus. Here, we present an unusual case of malignant PEComa arising in the buttock region.

Clinical characteristics and outcomes of patients with hepatic angiomyolipoma: A literature review

First reported in 1976, hepatic angiomyolipoma (HAML) is a rare mesenchymal liver tumor occurring mostly in middle-aged women. Diagnosis of the liver mass is often incidental on abdominal imaging due to the frequent absence of specific symptoms. Nearly 10% of HAMLs are associated with tuberous sclerosis complex. HAML contains variable proportions of blood vessels, smooth muscle cells and adipose tissue, which renders radiological diagnosis hazardous. Cells express positivity for HMB-45 and actin, thus these tumors are integrated into the group of perivascular epithelioid cell tumors. Typically, a HAML appears on magnetic resonance imaging (or computed tomography scan) as a hypervascular solid tumor with fatty areas and with washout, and can easily be misdiagnosed as other liver tumors, particularly hepatocellular carcinoma. The therapeutic strategy is not clearly defined, but surgical resection is indicated for symptomatic patients, for tumors showing an aggressive pattern (i.e., changes in size on imaging or high proliferation activity and atypical epithelioid pattern on liver biopsy), for large (> 5 cm) biopsy-proven HAML, and if doubts remain on imaging or histology. Conservative management may be justified in other conditions, since most cases follow a benign clinical course. In summary, the correct diagnosis of HAML is challenging on imaging and relies mainly on pathological findings.

Primary cutaneous malignant perivascular epithelioid cell tumor: Case of a rare tumor with review of the literature

Perivascular epithelioid cell tumors (PEComas) are mesenchymal neoplasms with characteristic epithelioid or spindled cytomorphology that typically grow around blood vessels. These tumors are phenotypically and immunohistochemically distinct, expressing markers of both melanocytic and smooth muscle differentiation. Herein, we describe a case of histopathologically malignant cutaneous PEComa without metastatic spread, with review of the pertinent literature. Telescoping punch biopsy demonstrated an epithelioid neoplasm with marked atypia, hypercellularity, and increased mitotic activity. Immunohistochemical stains for HMB-45, NK1-C3, PGP9.5, MiTF, CD10, and CD68 were positive within tumor cells. In addition, there was diffuse expression of caldesmon and focal cytoplasmic staining for smooth muscle actin on the excision specimen. The patient underwent treatment with surgical excision with adjuvant radiation and surveillance computed tomography (CT). The patient remains free of recurrence or metastatic disease after 10 months of follow-up. To our knowledge, this is only the third reported case of a malignant cutaneous PEComa reported in the literature to date.

PEComa-A Rare Liver Tumor

PEComa (perivascular epithelioid cell tumor) is a rare liver tumor. Decisions regarding patient management are currently based on a few small case series. The aim of this study was to report the clinicopathological features of PEComa in order to provide guidance for management, complemented by our own experience. This retrospective observational study included all patients with PEComa who underwent surgical treatment in two departments between 2002 and 2020. A total of 20 patients were diagnosed with PEComa following histopathological examination. The age of the patients ranged from 21 to 73 years. The majority of patients were women (85%). In most patients, the tumors were incidental. In diagnostic studies, PEComas with high arterial vascularization have been described. Liver resection was the treatment of choice. There was only one postoperative complication. During histopathological evaluation, tumors were composed mostly of epithelioid cells, rarely with spindle cell components, thick-walled vessels, and adipocytes in different proportions. Melanocytic markers (HMB45, MelanA) and at least one smooth muscle marker were expressed in all tumors. Features suggestive of malignancy were found in three cases. In conclusion, PEComa is a rare liver tumor that is usually diagnosed incidentally. In radiological studies, tumors with high arterial vascularization are observed. Liver resection is the treatment of choice.

Benign tumours of the bronchopulmonary system

The vast majority of tumours arising in the bronchopulmonary system are malignant in nature. Benign tumours of the lung are relatively rare and are often incidental findings during clinical investigations for unrelated conditions. These lesions can arise in the bronchial tree or the pulmonary parenchyma and may be of epithelial, mesenchymal, salivary gland-type or unknown differentiation. Although the spectrum of these lesions is wide, the clinical, pathological and immunohistochemical characteristics of the most relevant will be the subject of this review. In addition, the most important features allowing differentiation from malignant pulmonary neoplasms will be discussed.

VEGFR Inhibitors for Uterine Metastatic Perivascular Epithelioid Tumors (PEComa) Resistant to mTOR Inhibitors. A Case Report and Review of Literature

Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms. PI3K/AKT/mTOR pathway upregulation is critical for their pathogenesis and is often associated with TSC1/TSC2 inactivation. Although first line mTOR inhibitors are an effective treatment, metastatic PEComas eventually progress. A 53-year-old woman presented a 4-month history of post-menopausal vaginal bleeding. Clinical and radiological examination detected a uterine mass and a single S1 bone lesion. The patient underwent a radical hysterectomy and bone biopsy. The anatomopathological evaluation concluded to an oligo-metastatic uterine PEComa. The tumor harbored a heterozygous deletion of 9q34 that contains the TSC1 gene. Concerning the primary lesion, the resection was complete and the single bone metastasis was treated with radiotherapy. Three months later, the patient presented bone, lung and subcutaneous metastatic progression. An everolimus and denosumab treatment was initiated. After 2 years of treatment, a clinically significant bone, lung and subcutaneous progression was detected. Following a literature review of the possible therapeutic options, we initiated a second line treatment by pazopanib. This treatment resulted in regression of the subcutaneous lesions and stability of lung and bone metastases. In this challenging, rare setting, our report suggests single agent, anti-angiogenic, tyrosine kinase inhibitor to be effective as second line treatment of metastatic uterine PEComa progressing on mTOR inhibitors.

Histopathologic Characterization of Bladder Perivascular Epithelioid Cell Neoplasms (PEComa): A Series of 11 Cases With a Subset Having TFE3 Rearrangements

Perivascular epithelioid cell neoplasms (PEComas) of the bladder are extremely rare, with ~30 case reports. A subset of PEComas contain TFE3 gene rearrangement, however, the distinct histomorphologic features of these translocation tumors has not been fully explored in bladder PEComas. In our series, 11 cases of bladder PEComas were collected, including 1 internal and 10 consults, with 1 case previously reported. There was a female predominance (9 female, 2 male) with a mean age of 44.2 years (24 to 61 y). In only 1 of the 10 consult cases was PEComa considered in the differential diagnosis. In 10 of 11 cases, prominent epithelioid features were noted, with the final case having focal epithelioid morphology. Mitotic rate was increased in 2 of 11 cases, and 2 of 11 cases had cytological atypia. Two cases were malignant, with invasion into perivesicle tissue in 1 case, and metastases to lungs and brain followed by death in the other case. Immunohistochemically, there was strong, and diffuse staining for cathepsin K in 10/11 cases with the 1 negative case restained on a previously stained slide. HMB-45 was diffusely positive in 8/11 cases, while melan-A was present in only 1/10 cases. Muscle markers were variably expressed with positivity for both smooth muscle actin in 6/10 cases and desmin in 3/10 cases. Keratin AE1/3 was uniformly negative (0/11). In 5/8 cases where TFE3 was rearranged by fluorescence in situ hybridization, the morphology had a predominantly epithelioid, nested architecture. Overall, bladder PEComas are particularly difficult to diagnose given their rarity, are predominantly epithelioid and do not always express melanocytic markers. Diagnosis in the bladder requires a combination of morphologic characterization, exclusion of other diagnostic possibilities, positive Cathepsin K staining, variable melanocytic marker expression, with some cases showing a TFE3 gene rearrangement.