Perivascular Epithelioid Cell Research Articles

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

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

Gynecologic perivascular epithelioid cell tumors (PEComas): a review of recent evidence.

Gynecologic perivascular epithelioid cell (PEC) tumors, or 'PEComas,' represent a rare and intriguing subset of tumors within the female reproductive tract. This systematic literature review aims to provide an updated understanding of gynecologic PEComas based on available literature and data. Although PEComa is rare, there are varied tumor-site presentations across gynecologic organs, with uterine PEComas being the most prevalent. There is scarce high-quality literature regarding gynecologic PEComa, and studies on malignant PEComa underscore the challenges in diagnosis. Among the diverse mutations, mTOR alterations are the most prominent. Survival analysis reveals a high rate of local recurrence and metastatic disease, which commonly affects the lungs. Treatment strategies are limited, however mTOR inhibitors have pivotal role when indicated and chemotherapy may also be used. with some cases demonstrating promising responses. The paucity of data underscores the need for multicentric studies, an international registry for PEComas, and standardized reporting in case series to enhance clinical and pathological data.

Hepatic Pecoma versus Hepatocellular Carcinoma In The Noncirrhotic Liver on Gd-EOB-DTPA-Enhanced MRI: A Diagnostic Challenge.

Hepatic perivascular epithelioid cell tumors (PEComa) often mimic hepatocellular carcinoma (HCC) in patients without cirrhosis. This study aimed to develop a nomogram using imaging characteristics on Gd-EOB-DTPA-enhanced MRI and to distinguish PEComa from HCC in a noncirrhotic liver. Forty patients with non-cirrhotic Gd-EOB-DTPA-enhanced magnetic resonance imaging(MRI) were included in our study. A multivariate logistic regression model was used to select significant variables to distinguish PEComa from HCC. A nomogram was developed based on the regression model. The performance of the nomogram was assessed with respect to the ROC curve and calibration curve. Decision curve analysis (DCA) was performed to evaluate the clinical usefulness of the nomogram. Two significant predictors were identified: the appearance of an early draining vein and the T1D value of tumors. The ROC curve showed that the area under the curve (AUC) of the model to predict the risk of PEComa was 0.91 (95% CI: 0.80~1) and showed that the model had high specificity (92.3%) and sensitivity (88.9%). The nomogram incorporating these two predictors showed favorable calibration, which was validated using 1000 resampling procedures, and the corrected C-index of this model was 0.90. Furthermore, DCA analysis showed that the model had clinical practicability. In conclusion, the nomogram model showed favorable predictive accuracy for distinguishing PEComa from HCC in non-cirrhotic patients and may aid in clinical decision-making.

The "Other" Uterine Mesenchymal Neoplasms: Recent Developments and Emerging Entities.

Uterine mesenchymal neoplasms are a challenging group of tumors that often show overlapping morphologic features and immunohistochemical profiles. The increasing use of molecular testing in these tumors has enabled a better appreciation of their pathobiology, resulting in a wave of emerging neoplasms and improved characterization of ones previously considered exceptionally rare. Identification of specific molecular alterations has permitted targeted therapy options in tumors that were typically unresponsive to conventional therapies, as well as recognition that a subset can have a hereditary basis. This review will discuss the more "common" of the uncommon uterine mesenchymal neoplasms, including inflammatory myofibroblastic tumor, perivascular epithelioid cell tumor, uterine tumor resembling ovarian sex cord tumor, and embryonal rhabdomyosarcoma. This will be followed by an overview of emerging entities, including NTRK-rearranged uterine sarcoma, SMARCA4-deficient uterine sarcoma, KAT6B/A::KANSL1 fusion uterine sarcoma, and MEIS1::NCOA2/1 fusion sarcoma.

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

BackgroundPEComa 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 presentationA 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.ConclusionsA 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.

TFE3-Rearranged PEComa/PEComa-like Neoplasms: Report of 25 New Cases Expanding the Clinicopathologic Spectrum and Highlighting its Association With Prior Exposure to Chemotherapy.

Since their original description as a distinctive neoplastic entity, ~50 TFE3-rearranged perivascular epithelioid cell tumors (PEComas) have been reported. We herein report 25 new TFE3-rearranged PEComas and review the published literature to further investigate their clinicopathologic spectrum. Notably, 5 of the 25 cases were associated with a prior history of chemotherapy treatment for cancer. This is in keeping with prior reports, based mainly on small case series, with overall 11% of TFE3-rearranged PEComas being diagnosed postchemotherapy. The median age of our cohort was 38 years. Most neoplasms demonstrated characteristic features such as nested architecture, epithelioid cytology, HMB45 positive, and muscle marker negative immunophenotype. SFPQ was the most common TFE3 fusion partner present in half of the cases, followed by ASPSCR1 and NONO genes. Four of 7 cases in our cohort with meaningful follow-up presented with or developed systemic metastasis, while over half of the reported cases either recurred locally, metastasized, or caused patient death. Follow-up for the remaining cases was limited (median 18.5 months), suggesting that the prognosis may be worse. Size, mitotic activity, and necrosis were correlated with aggressive behavior. There is little evidence that treatment with MTOR inhibitors, which are beneficial against TSC-mutated PEComas, is effective against TFE3-rearranged PEComas: only one of 6 reported cases demonstrated disease stabilization. As co-expression of melanocytic and muscle markers, a hallmark of conventional TSC-mutated PEComa is uncommon in the spectrum of TFE3-rearranged PEComa, an alternative terminology may be more appropriate, such as "TFE3-rearranged PEComa-like neoplasms," highlighting their distinctive morphologic features and therapeutic implications.

Perivascular Epithelioid Cell-Family Tumors in Children, Adolescents and Young Adults:Clinicopathologic Features in 70 Cases.

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal tumors of uncertain histogenesis expressing smooth muscle and melanocytic markers. The clinicopathologic spectrum in young patients is not well documented. To describe a multi-institutional series of PEComas in children, adolescents, and young adults. PEComas, not otherwise specified (NOS); angiomyolipomas (AMLs); lymphangioleiomyomatosis; and clear cell sugar tumors were retrospectively identified from 6 institutions and authors' files. Seventy PEComas in 64 patients (median age, 15 years) were identified. They were more common in females (45 of 64 patients), occurring predominately in kidney (53 of 70), followed by liver (6 of 70). Thirty-four patients had confirmed tuberous sclerosis complex (TSC), 3 suspected TSC mosaicism, 2 Li-Fraumeni syndrome (LFS) and 1 neurofibromatosis type 1. Most common variants were classic (49 of 70) and epithelioid (8 of 70) AML. Among patients with AMLs, most (34 of 47) had TSC, and more TSC patients had multiple AMLs (15 of 36) than non-TSC patients (2 of 13). Two TSC patients developed malignant transformation of classic AMLs: 1 angiosarcomatous and 1 malignant epithelioid. Lymphangioleiomyomatosis (5 of 70) occurred in females only, usually in the TSC context (4 of 5). PEComas-NOS (6 of 70) occurred exclusively in non-TSC patients, 2 of whom had LFS (2 of 6). Three were malignant, 1 had uncertain malignant potential, and 2 were benign. All 4 PEComas-NOS in non-LFS patients had TFE3 rearrangements. Compared to the general population, TSC was more prevalent in our cohort; PEComas-NOS showed more frequent TFE3 rearrangements and possible association with LFS. This series expands the spectrum of PEComas in young patients and demonstrates molecular features and germline contexts that set them apart from older patients.

Abstract 6486: Correlation of nab-sirolimus tumor drug levels and improved tumor suppression in KRAS G12C non-small cell lung cancer xenografts treated with nab-sirolimus in combination with KRAS inhibitors

Abstract Background: KRAS mutations are found in a variety of tumor types, including non-small cell lung cancer (NSCLC), where KRAS G12C mutation is present in ~12% of NSCLC patients. KRAS G12C inhibitors (KRAS G12Cis), sotorasib and adagrasib, are approved for the treatment of KRAS G12C-mutated, locally advanced or metastatic NSCLC. The mTOR pathway is often activated in patients with KRAS mutations and may contribute to resistance to KRAS G12Cis. nab-Sirolimus is a nanoparticle albumin-bound intravenously (IV) administered form of the mTOR inhibitor (mTORi) sirolimus and is approved for the treatment of patients with advanced malignant perivascular epithelioid cell tumors. This study assessed tumor and blood drug level correlation with antitumor activity of nab-sirolimus or everolimus alone or in combination with KRAS G12Cis. Methods: Athymic mice bearing subcutaneous KRAS G12C- and STK11-mutated NSCLC xenografts (NCI-H2122) were treated with saline, mTORis nab-sirolimus (IV) or everolimus (oral) at clinically relevant and equal weekly dose of 15 mg/kg/wk, or KRAS G12Cis sotorasib (oral) or adagrasib (oral) at 30 mg/kg/day alone or in combination. Tumor volume changes from baseline were assessed; tumor and blood samples were harvested at the end of study (6 wks) for analysis of trough drug levels by LC-MS/MS, and tumor lysates were analyzed for downstream markers for mTOR inhibition by Western blot. Results: In nab-sirolimus plus KRAS G12Ci treated groups, significantly slower tumor growth was observed compared with single agent treated groups and everolimus plus KRAS G12Ci treated groups. Compared with single-agent nab-sirolimus (170.1 ng/g), treatment with nab-sirolimus plus sotorasib resulted in reduced tumor nab-sirolimus drug levels (73.6 ng/g, P=0.0040); while similar tumor nab-sirolimus drug levels were observed for nab-sirolimus plus adagrasib (121.6 ng/g, P=ns). Corresponding to greater antitumor activity, significantly greater tumor trough mTORi drug levels were observed in nab-sirolimus plus either sotorasib or adagrasib treated groups compared with similar everolimus combinations (85-fold, P<0.0001; and 91-fold, P=0.0050, respectively). Correspondingly, stronger mTOR downstream target inhibition of pS6 were observed for nab-sirolimus plus KRAS G12Ci treated groups compared with everolimus plus KRAS G12Ci treated groups. Conclusions: The addition of a KRAS G12Ci to nab-sirolimus significantly reduced tumor volume and increased tumor drug levels, suggesting enhanced tumor targeting compared with everolimus plus KRAS G12Cis and correlating to improved antitumor activity and mTOR target suppression. Clinical dose-finding studies are needed to determine potential drug-drug interactions between nab-sirolimus and KRASis. Citation Format: Shihe Hou, Jorge Nieva, Maria Zalath, Neil Desai. Correlation of nab-sirolimus tumor drug levels and improved tumor suppression in KRAS G12C non-small cell lung cancer xenografts treated with nab-sirolimus in combination with KRAS inhibitors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6486.

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.

Perivascular Epithelioid Cell Tumor with Uncertain Malignant Potential Arising in the Round Ligament.

A 12-year-old adolescent was diagnosed with a right-sided solid mass in the round ligament of the uterus. The chief complaints were abdominal pain and pelvic discomfort. She underwent laparoscopic tumor resection. Histological examination demonstrated a trabecular growth pattern of epithelioid cells with mitotic activity (3 per 50 HPF), which expressed melanocytic and myoid markers. Due to aforementioned findings, a final diagnosis of perivascular epithelioid cell tumor (PEComa) with uncertain malignant potential was made. To the best of our knowledge, this localization of PEComa is considered to be infrequent with only occasionally reported cases.

PEC-PRO: A new prognostic score from a series of 87 patients with localized perivascular epithelioid cell neoplasms (PEComas) treated with curative intent.

Perivascular epithelioid cell neoplasms (PEComas) encompass a heterogeneous family of mesenchymal tumors. Previously described clinicopathologic features aimed at distinguishing benign from malignant variants but lacked prognostic value. This retrospective analysis examined clinicopathologic data from patients who had localized PEComa across French Sarcoma Network centers. The authors analyzed 12 clinicopathologic features in a Cox proportional hazard framework to derive a multivariate prognostic risk model for event-free survival (EFS). They built the PEComa prognostic score (PEC-PRO), in which scores ranged from 0 to 5, based on the coefficients of the multivariate model. Three groups were identified: low risk (score=0), intermediate risk (score=1), and high risk (score≥2). Analyzing 87 patients who had a median 46-month follow-up (interquartile range, 20-74 months), the median EFS was 96.5 months (95% confidence interval [CI], 47.1 months to not applicable), with 2-year and 5-year EFS rates of 64.7% and 58%, respectively. The median overall survival was unreached, with 2-year and 5-year overall survival rates of 82.3% and 69.3%, respectively. The simplified Folpe classification did not correlate with EFS. Multivariate analysis identified three factors affecting EFS: positive surgical margins (hazard ratio [HR], 5.17; 95% CI, 1.65-16.24; p=.008), necrosis (HR, 3.94; 95% CI, 1.16-13.43; p=.030), and male sex (HR, 3.13; 95% CI, 1.19-8.27; p=0.023). Four variables were retained in the prognostic model. Patients with low-risk PEC-PRO scores had a 2-year EFS rate of 93.7% (95% CI, 83.8%-100.0%), those with intermediate-risk PEC-PRO scores had a 2-year EFS rate of 67.4% (95% CI, 53.9%-80.9%), and those with high-risk PEC-PRO scores had a 2-year EFS rate of 2.3% (95% CI, 0.0%-18.3%). The PEC-PRO score reliably predicts the risk of postoperative recurrence in patients with localized PEComa. It has the potential to improve follow-up strategies but requires validation in a prospective trial.

Prostatic perivascular epithelioid cell tumor: A rare entity and literature review

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm comprising perivascular epithelioid cells that express myomelanocytic immunophenotype, while stain negative for epithelial markers. We describe a case of prostatic PEComa in a 55-year-old man, who had one month history of frequent urination, hesitancy, and sensation of incomplete voiding. Radiological imaging disclosed prostatomegaly. Despite the medical treatment offered, episodes of urinary retention persisted. Subsequently, he underwent endoscopic transurethral resection of the prostate, histology showed tumor arranged in nests surrounded by thin delicate vessels. The tumor cells were epithelioid with abundant clear-to-eosinophilic cytoplasm, round nuclei, and inconspicuous nucleoli. Bizarre multinucleated giant cells, conspicuous mitosis and focal necrosis were evident. On immunohistochemistry, the tumor cells were diffusely positive for Human Melanoma Black (HMB45) and smooth muscle actin, negative for anti-cytokeratin monoclonal antibodies (AE1/AE3), Homeobox protein (NKX3.1), GATA Binding Protein 3 (GATA3), synaptophysin, Transcription Factor Binding to Immunoglobulin Heavy Constant Mu (IGHM) Enhancer 3 (TFE3), desmin, and SRY (sex determining region Y) -Box Transcription Factor 10 (SOX10). This uncommon case illustrates our diagnostic ordeal with a brief discussion on its nosology and a comprehensive literature review.

Phase II Trial of nab-Sirolimus in Patients With Advanced Malignant Perivascular Epithelioid Cell Tumors (AMPECT): Long-Term Efficacy and Safety Update.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.nab-Sirolimus is approved in the United States for the treatment of metastatic or locally advanced malignant perivascular epithelioid cell tumor (PEComa) on the basis of the primary analysis results of the phase II Advanced Malignant Perivascular Epithelioid Cell Tumors (AMPECT) trial (ClinicalTrials.gov identifier: NCT02494570). Results from the primary analysis were previously published; however, the median duration of response (mDOR) had not been reached at that time. Here, 3 years after the primary analysis, we report final efficacy and safety data (data cutoff: April 29, 2022). At study completion, the confirmed overall response rate (by independent radiologist review using RECIST v1.1) was 38.7% (95% CI, 21.8 to 57.8), with an additional converted confirmed complete response (n = 2). Median progression-free survival remained the same at 10.6 months (95% CI, 5.5 to 41.2). The mDOR was reached at 39.7 months (95% CI, 6.5 to not reached [NR]), and the median overall survival at completion was 53.1 months (95% CI, 22.2 to NR). The most common treatment-related adverse events (TRAEs) were stomatitis (82.4%) and fatigue and rash (each 61.8%). No new or unexpected adverse events occurred, and no grade ≥4 TRAEs were reported. These results highlight the long-term clinical benefit of nab-sirolimus in patients with advanced malignant PEComa, with a DOR of >3 years.

Abstract B010: Response to treatment with nab-sirolimus among patients with primary uterine tumors: A subgroup analysis from AMPECT

Abstract Introduction/objective: AMPECT (NCT02494570) is a pivotal study of nab-sirolimus in patients with malignant perivascular epithelioid cell tumors (PEComa). Malignant PEComa is an aggressive, rare sarcoma for which cytotoxic chemotherapies provide limited patient benefit. Inactivation of TSC1 or TSC2 tumor suppressor genes, upstream of mTORC1, is commonly associated with malignant PEComa; these mutations occurred in 56% of patients in AMPECT. nab-Sirolimus is an mTOR inhibitor (mTORi) that utilizes albumin-bound nanoparticle technology to drive higher intratumoral drug levels and more complete pathway suppression than conventional mTORis. nab-Sirolimus is approved in the USA for the treatment of advanced or metastatic malignant PEComa based on the primary analysis results of the AMPECT trial, which showed a confirmed overall response rate (ORR) of 39%, regardless of mutation status. We describe outcomes of a subset of patients with primary uterine PEComa, representing 23% of efficacy-evaluable patients in AMPECT. Methods: AMPECT was an open-label, multicenter, phase 2 registration study in mTORi-naïve adult patients (≥18 years old) with a histologically confirmed diagnosis of malignant PEComa and Eastern Cooperative Oncology Group performance status score ≤1. Patients received nab-sirolimus 100 mg/m2 intravenously on days 1 and 8 of a 21-day cycle until progression or unacceptable toxicity. The primary endpoint was ORR by independent radiology review. Key secondary endpoints included time to response, duration of response (DOR), and safety. Results: A total of 7 patients with uterine PEComa were treated with nab-sirolimus in AMPECT and were evaluable for both safety and efficacy. Mean ± SD age was 60.0 ± 13.4 years, and 71% (5/7) of patients were White. ORR was 43% (3/7 patients); all 3 were confirmed partial responses and were seen in patients with tumors with somatic inactivating alterations in TSC1 or TSC2. Two (29%) patients had best response of stable disease. For the 3 responders, time to response was 1.4, 1.4, and 1.5 months, and DOR was 5.6, 36.0+, and 39.7 months. All 7 patients had ≥1 treatment-related adverse event (TRAE; grade 3, 43%); no grade ≥4 or serious TRAEs occurred. Conclusions: Rates of response to treatment and safety findings in patients with primary uterine PEComa treated with nab-sirolimus in AMPECT were consistent with those previously reported in the overall patient population. Responses were rapid and durable. Notably, all responders had TSC1 or TSC2 alterations; however, there were too few patients in this subset to draw conclusions regarding efficacy in tumors without these alterations. nab-Sirolimus is being further evaluated in a tumor-agnostic trial of patients with TSC1 or TSC2 inactivating alterations (PRECISION I; NCT05103358). Citation Format: Vinod Ravi, Mark A. Dickson, Kristin Ganjoo, Li Ding, Anita N. Schmid, Norma A. Palma, Willis H. Navarro, Andrew J. Wagner. Response to treatment with nab-sirolimus among patients with primary uterine tumors: A subgroup analysis from AMPECT [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr B010.

Abstract A018: A phase 2, open-label, single-arm, prospective, multicenter study of nab-sirolimus plus letrozole in advanced or recurrent endometrioid endometrial cancer

Abstract Introduction/Objective: This trial in progress is designed to evaluate the anti-tumor activity of nab-sirolimus in combination with letrozole in patients with advanced or recurrent endometrioid endometrial carcinoma (EEC). Despite recent pivotal data demonstrating improved outcomes with immunotherapy plus chemotherapy, regardless of mismatch repair status, alternative treatment options, particularly for advanced or recurrent EEC remain necessary. Dysregulation of mammalian target of rapamycin (mTOR) signaling is implicated in the pathology of EEC, in which >80% harbor PTEN or PI3K/AKT/mTOR pathway alterations. Moreover, crosstalk between mTOR and estrogen receptor signaling pathways is associated with endocrine resistance. GOG-3007 and other phase 2 studies have demonstrated that the combination of conventional mTOR inhibitors (mTORis) and endocrine therapy provides clinical benefit in patients with EC. nab-Sirolimus, a nanoparticle injectable form of mTORi, is approved in the USA for malignant perivascular epithelioid cell tumor. Preclinical data of nab-sirolimus demonstrated improved tumor accumulation, mTOR inhibition, and tumor growth suppression compared with conventional mTORis. We hypothesize that nab-sirolimus in combination with letrozole may produce synergistic antitumor activity in patients with recurrent EEC. Methods: In this phase 2, open-label, single-arm, multicenter study (NCT05997017), nab-sirolimus (100 mg/m2, intravenous, on days 1 and 8 of each 21-day cycle) and letrozole (2.5 mg, oral, daily) are administered to patients (~29 planned) with clinically confirmed, advanced, or recurrent EEC. Eligibility criteria include age ≥18 years, ≤1 prior chemo-based regimen, Eastern Cooperative Oncology Group performance status score 0 or 1, naïve to mTORi, and measurable disease (per Response Evaluation Criteria in Solid Tumors [RECIST] v1.1). The primary endpoint is best overall response rate by RECIST v1.1. Key secondary endpoints include duration of response, progression-free survival, overall survival, and safety. The relationship between biomarkers and response outcomes is an exploratory endpoint. Citation Format: Lauren E. Dockery, Anna Priebe, Linda Duska, Angela K. Green, Cara Mathews, Fernanda Musa, David O'Malley, Allison Puechl, Li Ding, Anita N. Schmid, Willis H. Navarro, Brian Slomovitz, Kathleen Moore. A phase 2, open-label, single-arm, prospective, multicenter study of nab-sirolimus plus letrozole in advanced or recurrent endometrioid endometrial cancer [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr A018.

Abstract B011: Phase 2, multicenter, open-label basket trial of nab-sirolimus for malignant solid tumors harboring pathogenic inactivating alterations in TSC1 and TSC2 (PRECISION I)

Abstract Introduction/objective: PRECISION I (NCT05103358) is an ongoing trial of nab-sirolimus in advanced cancers harboring pathogenic inactivating alterations in TSC1 or TSC2. TSC1 and TSC2 alterations have been observed in patients with various cancers, including the most common cancer of the female reproductive organs, endometrial cancer, where ~3% contain TSC1 and/or TSC2 alterations. nab-Sirolimus, approved in the USA for patients with advanced malignant perivascular epithelioid cell tumor (PEComa), is an albumin-bound mTOR inhibitor (mTORi) that inhibits the mTOR pathway via suppression of the mTORC1 complex. When TSC1 or TSC2 is inactivated via mutation or loss, the mTOR pathway may be aberrantly activated. In an exploratory analysis of AMPECT (NCT02494570), a pivotal trial of nab-sirolimus in advanced malignant PEComa, 64.3% (9/14) of patients with pathogenic inactivating TSC2 or TSC1 alterations had a confirmed response. Most treatment-related adverse events in AMPECT were grade 1/2 (none were grade ≥4) and were consistent with mTORi-class adverse events. Based on the clinical observations from AMPECT and the underlying mechanism of action of nab-sirolimus, the PRECISION I trial was designed to assess the safety and efficacy of nab-sirolimus in a tumor-agnostic study of patients with advanced cancers with TSC1 or TSC2 inactivating alterations. Patients with endometrial cancer are expected to be enrolled based on the frequency of TSC1 and TSC2 inactivating alterations. Methods: Eligible patients are ≥12 years old and mTORi-naïve, possess advanced or metastatic malignant solid tumors with TSC1 or TSC2 inactivating alterations identified using next-generation sequencing (NGS) in tumor tissue or liquid biopsy (confirmed by central review of NGS reports), and have received appropriate standard treatments, per investigator. nab-Sirolimus 100 mg/m2 is given intravenously over 30 min on days 1 and 8 of each 21-day cycle. The primary endpoint is overall response rate per independent radiographic review (IRR) using Response Evaluation Criteria in Solid Tumors v1.1. Other endpoints include duration of response, time to response, progression-free survival by IRR, overall survival, patient-reported quality of life, and safety. Trial Status: Enrollment began in March 2022 and is expedited through collaboration with leading NGS providers; ongoing study access is facilitated through a just-in-time approach to trial location activation. Citation Format: Debra L. Richardson, Gopa Iyer, Li Ding, Anita N. Schmid, Willis Navarro, David Kwiatkowski, Jordi Rodon Ahnert. Phase 2, multicenter, open-label basket trial of nab-sirolimus for malignant solid tumors harboring pathogenic inactivating alterations in TSC1 and TSC2 (PRECISION I) [abstract]. In: Proceedings of the AACR Special Conference on Endometrial Cancer: Transforming Care through Science; 2023 Nov 16-18; Boston, Massachusetts. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(5_Suppl):Abstract nr B011.

Evaluation of TRIM63 RNA in situ hybridization (RNA-ISH) as a potential biomarker for alveolar soft-part sarcoma (ASPS)

Alveolar soft-part sarcoma (ASPS) is a rare soft tissue tumor with a broad morphologic differential diagnosis. While histology and immunohistochemistry can be suggestive, diagnosis often requires exclusion of other entities followed by confirmatory molecular analysis for its characteristic ASPSCR1-TFE3 fusion. Current stain-based biomarkers (such as immunohistochemistry for cathepsin K and TFE3) show relatively high sensitivity but may lack specificity, often showing staining in multiple other entities under diagnostic consideration. Given the discovery of RNA in situ hybridization (RNA-ISH) for TRIM63 as a sensitive and specific marker of MiTF-family aberration renal cell carcinomas, we sought to evaluate its utility in the workup of ASPS. TRIM63 RNA-ISH demonstrated high levels (H-score greater than 200) of expression in 19/20 (95%) cases of ASPS (average H-score 330) and was weak or negative in cases of paraganglioma, clear cell sarcoma, rhabdomyosarcoma, malignant epithelioid hemangioendothelioma, as well as hepatocellular and adrenal cortical carcinomas. Staining was also identified in tumors with known subsets characterized by TFE3 alterations such as perivascular epithelioid cell neoplasm (PEComa, average H-score 228), while tumors known to exhibit overexpression of TFE3 protein without cytogenetic alterations, such as melanoma and granular cell tumor, generally showed less TRIM63 ISH staining (average H-scores 147 and 96, respectively). Quantitative assessment of TRIM63 staining by RNA-ISH is potentially a helpful biomarker for tumors with molecular TFE3 alterations such as ASPS.

Hepatic and perihepatic PEComas: A study describing a series of five rare cases.

Perivascular epithelioid cell tumors (PEComas) encompass a group of rare mesenchymal neoplasms, with dual melanocytic and muscular differentiation. Hepatic PEComas are rare and difficult to diagnose, and their behavior is still unclear. Herein, we report a total of five cases of hepatic and perihepatic PEComas over a period of the last 5 years from our and collaborating center's archive. A detailed histological evaluation was done. A comprehensive panel of immunohistochemical stains was used and fluorescence in-situ hybridization analysis was performed for the TFE3 gene using break-apart probes. All these patients were women, with an average age of presentation of 44 years. The lesions were in the right hepatic lobe: three cases, the left hepatic lobe: one case, and gastrohepatic ligament: one case. The preoperative clinicoradiological diagnoses were hepatocellular carcinoma (HCC), focal nodular hyperplasia, hemangioma, metastasis, and gastrointestinal stromal tumor, respectively. Surgical excision was performed in four cases with no further adjuvant therapy. Histopathological examination and subsequent immunophenotyping revealed a diagnosis of PEComa. Fluorescence in-situ hybridization analysis was performed for TFE3 gene rearrangement in four cases. This series highlights the fact that accurate histological diagnosis of hepatic or perihepatic PEComas is important to prevent unnecessary aggressive treatment, unlike primary hepatocellular carcinomas or hepatoid/epithelioid metastatic tumors.

Benign Perivascular Epithelioid Cell Tumor of the Mesentery Misdiagnosed as a Uterine Fibroid: A Case Report and Review of Literature

BACKGROUND: Perivascular epithelioid cell tumor (PEComa) is a type of mesenchymal tumor composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. Benign mesenteric PEComa is a rare entity as there has been only one case reported so far. We are presenting a case of benign mesenteric PEComa in a 30-year-old female that presented with abdominal pain and was diagnosed by microscopic morphological examination and immunohistochemical staining. The aim of this case report is to make health-care professionals aware of the diagnostic criteria in similar presentations, treatment modalities offered for this patient, and others reported over the years for malignant as well as benign PEComas and also shedding the light on a new presentation and diagnosis. CASE REPORT: We reported a case of a 30-year-old female who presented with abdominal pain radiating to the back and rectum. After a thorough physical examination which was unremarkable, a CT scan was done which showed a mesenteric mass. This mass was then resected and sent for histopathology which revealed a PEComa. We report the history, clinical findings, laboratory reports, and gross imaging of a 30-year-old female who presented to our clinic and was diagnosed with a very rare benign mesenteric PEComa. CONCLUSION: PEComa is a rare tumor, and as PEComas arising from the mesentery being one of the rarer kinds with only 10 cases reported and this case being the 11th, out of those ten cases, only two of them were found to be benign which makes the case we are reporting the second benign mesenteric PEComa reported in English Literature.

18 F-FAPI for Imaging Metastatic Perivascular Epithelioid Cell Neoplasm.

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.