Perivascular epithelioid cell tumor ('PEComa') of the uterus: a subset of HMB-45-positive epithelioid mesenchymal neoplasms with an uncertain relationship to pure smooth muscle tumors

Uterine perivascular epithelioid cell tumors (PEComa) and the accuracy of proposed classification systems in predicting the malignant versus non-malignant behavior

OBJECTIVE

To compare the accuracy of available classification systems (Folpe, modified Folpe, Bennet, and Schoolmester) in predicting the behavior of uterine Perivascular Epithelioid Cell tumors (PEComas).

METHODS

We reviewed the pathology registry to identify all uterine PEComas treated at our center. We conducted a systematic literature review searching electronic databases from inception to November 2023. We included all references reporting at least one case of uterine PEComa; cases associated with tuberous sclerosis complex were excluded. Patient-level data were extracted by identified records. Survival analysis was used to assess the accuracy of all proposed classification systems to classify uterine PEComas as malignant versus non-malignant.

RESULTS

Six uterine PEComas were treated at our center. The literature search identified 101 uterine PEComas from 32 studies. Eighty-five out of 107 PEComas (28 studies and our series) reported enough follow-up data and details to apply all four classifications. The modified Folpe classification demonstrated the highest hazard ratio (HR) for relapse (HR:8.63; 95% confidence interval [CI] 2.06-36.1) and death due to PEComa (HR:6.8, 95%CI:0.89-51.6) for malignant versus non-malignant PEComas. Changing the cut-off of PEComa size to ≥8 cm and mitotic figures per 50 high power fields to ≥5, the HR for recurrence lowered (HR:6.26; 95% CI 2.20-17.80), but HR for death increased (HR:10.3; 95% CI 1.35-77.80).

CONCLUSIONS

The modified Folpe classification was the most accurate in predicting the PEComa behavior. Changing the cut-off of PEComa size and number of mitotic figures may improve the accuracy in predicting death due to disease.

Uterine Mesenchymal Tumors: Updates on Pathology, Molecular Landscape, and Therapeutics

Background: Mesenchymal uterine tumors are a diverse group of neoplasms with varying biological potential. Many of these neoplasms can have overlapping morphologic similarities, which, in some instances, render their diagnosis and categorization thorough histomorphologic examination inconclusive. In the last decade, an exponential amount of molecular data aiming to more accurately characterize and, consequently, treat these tumors have accumulated. Objective: The goal of this narrative review is to provide a pathologic review, a genetic update, and to know the new therapeutic avenues of primary uterine mesenchymal neoplasms.

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.

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.

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.

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.

Clinicopathological features of two ultra-rare cases of malignant perivascular epithelioid cell tumors (PEComas) involving the uterus with recent updates

Malignant perivascular epithelioid tumors (PEComas) involving the uterus are uncommon. Herein, we present the clinicopathological features of two such cases, including their diagnostic implications with recent updates. A 62-year-old lady presented with vaginal bleeding. Ultrasonogram revealed a heterogeneous uterine mass. She underwent an endometrial biopsy and total abdominal hysterectomy with bilateral salpingo-oophorectomy (TAH-BSO), which revealed a 3.2 cm-sized proliferative tumor in the fundus. A 45-year-old lady presented with recurrent abdominal pain. She underwent cytoreductive surgery twice with adjuvant chemotherapy for multiple tumors and TAH-BSO for a uterine tumor, 2 years before. Microscopic examination of both tumors revealed markedly atypical, polygonal-shaped/epithelioid tumor cells containing eosinophilic cytoplasm and arranged in a nesting pattern with intervening thin-walled blood vessels, mitotic figures (≥ 6/10 high power fields (hpfs)), and tumor necrosis. Tumor infiltration was more than half the myometrial thickness in the first tumor and pelvic nodal metastasis. The second tumor revealed rhabdoid-like and vacuolated cells along with "spider-like" giant cells. Immunohistochemically, both the tumors were positive for HMB45 and desmin, while negative for epithelial markers. Additionally, the second tumor was positive for smooth muscle actin (SMA) and TFE3. Both patients developed tumor recurrences. In view of multiple tumor deposits, the second patient was induced with a mammalian target of rapamycin (m-TOR) inhibitor (everolimus) but unfortunately died of the disease. Malignant PEComas involving the uterus are ultra-rare, aggressive tumors. An index of suspicion, based on certain histomorphological features, supported by immunohistochemical expression of myomelanocytic markers is necessary for a correct diagnosis. Certain PEComas display TFE3 positivity. A correct diagnosis has significant implications, including an aggressive clinical course and the possibility of targeted therapy, especially in recurrences or metastasis.

Malignant lung PEComa (clear cell tumor): rare case report and literature review

Clear cell tumors of the lung (CCTL), or "sugar tumors" of lung, are very uncommon lesions and are mostly benign perivascular epithelioid cell (PEC) tumors with no specific morphologic features. Fewer than 100 cases have been reported; the aggressive nature demonstrated in sporadic reports has rarely been described in the literature. Although the course is generally described as benign, eight reported cases showed malignant behavior. We report a case of a PEC with a malignant presentation in a young man, correlating the main characteristics of the tumor with other cases reported in the literature to better elucidate this rare presentation. We also performed a literature review of reports on benign and malignant CCTL cases, with a focus on clinical, imaging, and immunohistochemical differentiation. CCTLs are rare tumors that require histopathological and immunohistochemical confirmation; to date, criteria that can predict malignant evolution are lacking.

Uterine collision tumor (PEComa and endometrioid carcinoma) in a tuberous sclerosis patient: a case report

Perivascular epithelioid cell tumors are very rare mesenchymal neoplasms arising in various locations, such as the female genital tract, kidney, lung, prostate, bladder, pancreas, soft tissues, and bone. They possess a unique immunophenotype, co-expressing myogenic and melanocytic markers; molecular findings include mutations of tuberous sclerosis complex and translocations of transcription factor E3, a member of the microphthalmia transcription factor gene family. We herewith report a uterine collision tumor consisting of a perivascular epithelioid cell tumor and a moderately differentiated endometrial endometrioid carcinoma in a patient with genetically proven tuberous sclerosis; two leiomyomas were also found in contact with the tumor. Although two such cases one with a benign and another with a malignant perivascular epithelioid cell tumor have previously been reported, ours is, to our knowledge, the first reported in a tuberous sclerosis patient.

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.

Malignant perivascular epithelioid cell tumor (PEComa) of the uterus

BACKGROUND

Perivascular epithelioid cell tumors (PEComas) of the uterus is a rare type of mesenchymal tumors associated with myelomelanocytic differentiation and distinctive histological appearances. So far, the reported cases of uterine PEComas are usually benign. Documented malignant cases with aggressive behavior appear to be less common.

CASE PRESENTATION

We report a 37-year-old female who received abdominal hysterectomy for uterine tumor in a local hospital. She was diagnosed with uterine leiomyosarcoma and referred to Hubei Cancer Hospital. Her histological slides were reviewed and immunohistochemical staining for specific markers of epithelial, melanocytic, myoid and some others were analyzed. The pathologic diagnosis was malignant uterine PEComa. Systematic imaging of the patient further revealed an abdominal para-aortic mass. She received pelvic and para-aortic lymph node dissection. Postoperative histology revealed para-aortic lymph nodal metastasis of malignant uterine PEComa. She received 8 cycles of chemotherapy after surgery. The chemotherapy regiment was epirubicin plus ifosfamide The patient is free of recurrence and metastasis 6 years after surgical resection.

CONCLUSION

Uterine PEComas are indistinguishable from other uterine tumors such as leiomyoma and leiomyosarcoma before pathologic diagnosis could be made. For patients with malignant uterine PEComas, removal of both primary lesions and metastatic foci, if any, needs to be attempted. Postoperative chemotherapy or radiotherapy should also be considered in patients with distant metastases or positive lymph nodes.

Data Set for Reporting of Uterine Malignant and Potentially Malignant Mesenchymal Tumors: Recommendations From the International Collaboration on Cancer Reporting (ICCR)

The International Collaboration on Cancer Reporting (ICCR) seeks to produce standardized, evidence-based protocols for the reporting of tumors with the aim of ensuring that all cancer reports generated worldwide will be of similar high quality and record the same elements. Herein, we describe the development of the data set for the reporting of uterine malignant and potentially malignant mesenchymal tumors by a panel of expert pathologists and a single clinician and provide the commentary and rationale for the inclusion of core and noncore elements. This data set, which incorporates the recent updates from the 5th edition of the World Health Organization Classification of Female Genital Tumors, addresses several subjects of debate including which mesenchymal tumors should be graded, how to document extent of invasion, mitotic counts, and the role of ancillary testing in tumor diagnosis and patient management. The inclusion of elements is evidence-based or based on consensus of the expert panel with clinical relevance being the guiding standard.

Uterine Leiomyosarcoma Masquerading as a Malignant Perivascular Epithelioid Cell Tumor: A Diagnostic Challenge

Uterine sarcomas with myomelanocytic differentiation have been reported to be diagnostically challenging. We report a case of uterine leiomyosarcoma with extensive perivascular epithelioid cell tumor (PEComa)-like areas and extrauterine metastases. The patient was a 49-year-old gravida 3 para 2 Japanese woman with no relevant medical history. She noticed a vaginal mass with bleeding. Imaging examination revealed a uterine tumor and multiple liver and lung metastases. The vaginal tumor (3.5 cm) was resected and diagnosed as a malignant PEComa based on morphology and myomelanocytic marker expression. Clinically used targeted sequencing (FoundationOneCDx™) revealed gene alterations in RB1, TP53, and ATRX but not TSC1/2. Despite administration of an mTOR inhibitor, the tumor size increased, and subsequently, hysterectomy was performed to relieve the symptoms. The uterine tumor was composed of conventional leiomyosarcoma showing RB1 loss, wild-type TP53 staining, and retained ATRX expression, as well as adjacent predominant PEComa-like components with RB1 loss, TP53 overexpression, and ATRX loss, identical to the characteristics of the vaginal tumor. In the uterine tumor, both HMB-45 and MITF were weak to moderately positive for approximately 40% of tumor cells while Melan-A was negative. The tumor was finally diagnosed as leiomyosarcoma with PEComa-like features. This case exemplifies the tumorigenesis of diagnostically challenging tumors with myomelanocytic differentiation and demonstrates the importance of integrating multiple types of information, including genomic profiling, in making a correct diagnosis leading to appropriate treatment.

Update on Uterine Mesenchymal Neoplasms

This review focuses on recent advances in epithelioid and myxoid uterine mesenchymal neoplasms, a category of tumors whereby diagnostic criteria have been rapidly evolving due to advances in molecular testing. Pertinent clinicopathological and molecular features are highlighted for perivascular epithelioid cell tumors, uterine tumors resembling ovarian sex cord tumors, BCOR/BCORL1-altered high-grade endometrial stromal sarcomas, and inflammatory myofibroblastic tumors. Novel developments in epithelioid and myxoid leiomyosarcomas are briefly discussed, and differential diagnoses with key diagnostic criteria are provided for morphologic mimickers.

Cutaneous Melanomas: A Single Center Experience on the Usage of Immunohistochemistry Applied for the Diagnosis

Cutaneous melanoma (cM) is the deadliest of all primary skin cancers. Its prognosis is strongly influenced by the stage at diagnosis, with early stages having a good prognosis and being potentially treatable with surgery alone; advanced stages display a much worse prognosis, with a high rate of recurrence and metastasis. For this reason, the accurate and early diagnosis of cM is crucial-misdiagnosis may have extremely dangerous consequences for the patient and drastically reduce their chances of survival. Although the histological exam remains the "gold standard" for the diagnosis of cM, a continuously increasing number of immunohistochemical markers that could help in diagnosis, prognostic characterization, and appropriate therapeutical choices are identified every day, with some of them becoming part of routine practice. This review aims to discuss and summarize all the data related to the immunohistochemical analyses that are potentially useful for the diagnosis of cM, thus rendering it easier to appropriately applicate to routine practice. We will discuss these topics, as well as the role of these molecules in the biology of cM and potential impact on diagnosis and treatment, integrating the literature data with the experience of our surgical pathology department.

Uterine PEComas: correlation between melanocytic marker expression and TSC alterations/TFE3 fusions

Uterine PEComas often present a diagnostic challenge as they share morphological and immunohistochemical features with smooth muscle tumors. Herein we evaluated a series of 19 uterine PEComas to compare the degree of melanocytic marker expression with their molecular profile. Patients ranged from 32-77 (median 48) years, with six tumors classified as malignant based on the modified gynecologic-specific prognostic algorithm. All patients with malignant PEComas were alive with disease or dead  of disease at last follow-up, while all those of uncertain malignant potential were alive and well (median follow-up, 47 months).Seventeen of 19 (89%) PEComas harbored either a TSC1 or TSC2 alteration. One of the two remaining tumors showed a TFE3 rearrangement, but the other lacked alterations in all genes evaluated. All showed at least focal (usually strong) positivity for HMB-45, with 15/19 (79%) having >50% expression, while the tumor lacking TSC or TFE3 alterations was strongly positive in 10% of cells. Melan-A and MiTF were each positive in 15/19 (79%) tumors, but staining extent and intensity were much more variable than HMB-45. Five of six (83%) malignant PEComas also harbored alterations in TP53, ATRX, or RB1, findings not identified in any tumors of uncertain malignant potential. One malignant PEComa was microsatellite-unstable/mismatch repair protein-deficient.In summary, TSC alterations/TFE3 fusions and diffuse (>50%) HMB-45 expression are characteristic of uterine PEComas. In morphologically ambiguous mesenchymal neoplasms with myomelanocytic differentiation, especially those with metastatic or recurrent disease, next-generation sequencing is recommended to evaluate for TSC alterations; as such, patients can be eligible for targeted therapy.

TSC2-mutant uterine sarcomas with JAZF1-SUZ12 fusions demonstrate hybrid features of endometrial stromal sarcoma and PEComa and are responsive to mTOR inhibition

Uterine perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal neoplasm that occasionally shares morphologic and immunohistochemical overlap with low- and high-grade endometrial stromal sarcoma (LGESS and HGESS). In this study, we sought to characterize the clinical, morphologic, genetic, and epigenetic features of five uterine sarcomas that display histologic features of LGESS, HGESS, and PEComa. All tumors demonstrated epithelioid cells often associated with a low-grade spindled component resembling LGESS, with both regions expressing CD10, ER, PR, variable HMB45, and Melan-A immunoreactivity, and strong cathepsin K and pS6 expression. Targeted massively parallel sequencing analysis revealed the presence of somatic TSC2 mutations in all five cases, of which four harbored concurrent or consecutive JAZF1-SUZ12 gene fusions. Unsupervised hierarchical clustering analysis of methylation profiles of TSC2-mutant uterine sarcomas (n = 4), LGESS (n = 10), and HGESS (n = 12) demonstrated two clusters consisting of (1) all LGESS and TSC2-mutant uterine sarcomas and (2) all HGESS. KEGG pathway analysis detected methylation differences in genes involved in PI3K/AKT, calcium, and Rap1 signaling. TSC2-mutant uterine sarcomas were responsive to hormone suppression, and mTOR inhibition demonstrated clinical benefit in four patients with these neoplasms. Our results suggest that these tumors represent histologically distinctive LGESS with TSC2 mutations. TSC2 mutations and JAZF1-SUZ12 fusion may help diagnose these tumors and possibly direct effective treatment.

Gynaecological perivascular epithelioid cell tumour (PEComa): comparative analysis of proposed algorithms for prediction of clinical outcome

AIMS

Perivascular epithelioid cell tumours (PEComas) are rare mesenchymal tumours that coexpress smooth muscle and melanocytic markers. They have a predilection for gynaecological organs, where they present a unique diagnostic challenge, because of morphological and immunohistochemical overlap with more common smooth muscle and stromal tumours. Limited information regarding the natural history, owing to the rarity of this tumour, makes accurate risk stratification difficult. We aimed to review clinicopathological features of gynaecological PEComa and compare accuracy of five different classification systems for prediction of prognosis.

METHODS AND RESULTS

We have described the clinicopathological features of 13 new cases and tested five prognostic algorithms in a total of 67 cases of gynaecological PEComa. Receiver operating characteristic curves were constructed and areas under the curve (AUCs) were calculated to evaluate predictive accuracy. The modified gynaecological-specific algorithm showed high sensitivity and specificity and yielded the highest AUC (0.864). It's earlier version, the gynaecological-specific algorithm, suffered from lower specificity (AUC = 0.843). The post-hoc McNemar test confirmed significant differences between the performances of the modified gynaecological-specific algorithm and the gynaecological-specific algorithm (P = 0.008). The original Folpe algorithm for PEComas of all sites showed low specificity, had a lower AUC (0.591), and was inapplicable in 18% of cases. Its two later versions (the revised Folpe algorithm and the modified Folpe algorithm) also yielded lower AUCs (0.690 and 0.591, respectively).

CONCLUSION

We have shown that the modified gynaecological-specific algorithm predicts the clinical outcome of gynaecological PEComa with high accuracy, and have validated its use for prognostic stratification of gynaecological PEComa.

A Retrospective Case Study of 13 Uterine Perivascular Epithelioid Cell Neoplasm (PEComa) Patients

Introduction and Hypothesis

Perivascular epithelioid cell neoplasms (PEComas) are rare mesenchymal tumors that originate from perivascular epithelioid cells. The uterus is the second most common organ to be affected by PEComa. Most PEComas are benign and the prognosis is usually good. Surgery is the main treatment at present, and adjuvant therapy is mainly used for malignant cases. However, because of the lack of described cases, the best diagnosis and treatment of these tumors cannot be determined.

Methods

From 2009 to 2020, 13 patients from Shengjing Hospital (China Medical University), with uterine PEComa, who met the inclusion criteria and appropriate pathological diagnosis were enrolled in this study. Clinical, pathological, and therapeutic features were retrospectively analyzed to determine the best approach towards diagnosis and treatment.

Results

All the enrolled patients underwent surgical treatment; four of them had a malignant PEComa. Three of the malignant patients received chemotherapy after surgery; among them, one died, another showed no obvious recurrence after regular re-examination, and the third did not undergo any further treatment despite short-term recurrence. However, upon regular re-examination, no progress was observed. The fourth malignant patient did not receive chemotherapy after surgery and showed no obvious recurrence during regular reviews.

Conclusion

The preoperative diagnosis of uterine PEComa lacks specificity and therefore is often confused with uterine leiomyoma or leiomyosarcoma. We conclude that uterine PEComa can be diagnosed by combined analysis of immunohistochemistry and post-operative pathology. Though surgical resection is still the main treatment, high-risk patients can be given adjuvant treatment to strengthen disease control.

Coexistence of Conventional Leiomyoma, Fumarate Hydratase-deficient Atypical Leiomyoma, and Perivascular Epithelioid Cell Tumor in a Uterus: A Case Study

A 44-yr-old woman with menorrhagia and uterine fibroids underwent total laparoscopic hysterectomy, revealing several submucosal, intramural, and subserosal tan-white nodules in the uterus. Microscopic examination revealed tumors displaying 3 distinct morphologies: 1 tumor with features of conventional leiomyoma; 1 tumor with increased cellularity, staghorn/hemangiopericytoma-like vasculature, and occasional atypical cells with prominent red nucleoli and some perinucleolar halos suggesting a fumarate hydratase (FH)-deficient atypical leiomyoma; and 1 tumor with an admixture of epithelioid and spindled cells with the former arranged around blood vessels suggesting a perivascular epithelioid cell tumor (PEComa). Immunohistochemical studies confirmed these diagnoses by demonstrating loss of FH expression in the atypical leiomyoma and diffuse expression of HMB45 and cathepsin K in the tumor with epithelioid features. Sanger sequencing analysis revealed that the FH-deficient atypical leiomyoma harbored a c.181A>G (p.Lys61Glu) mutation in exon 2 of the FH gene. As this mutation was not present in either the other tumors or peripheral blood, the mutation is somatic and hereditary leiomyomatosis and renal cell cancer syndrome is excluded. This case highlights the importance of thorough examination of uterine mesenchymal tumors with atypical and epithelioid features so that tumors with some potential for recurrence (PEComas) and those that might indicate a hereditary cancer syndrome (FH-deficient atypical leiomyoma) are identified and can trigger appropriate clinical investigation and follow-up.

Genomic Profiling Aids Classification of Diagnostically Challenging Uterine Mesenchymal Tumors With Myomelanocytic Differentiation

Although diagnosis of high-grade uterine mesenchymal tumors (UMTs) exhibiting classic morphologic features is straightforward, diagnosis is more challenging in tumors in which prototypical features are poorly developed, focal, and/or coexist with features seen in other neoplasms. Here, we sought to define the repertoire of somatic genetic alterations in diagnostically challenging UMTs with myomelanocytic differentiation, including some reported as perivascular epithelioid cell tumors (PEComas). In 17 samples from 15 women, the tumors were histologically heterogenous. Immunohistochemical expression of at least 1 melanocytic marker (HMB45, Melan-A, or MiTF) was identified in all tumors, and of myogenic markers (desmin or smooth muscle actin) in most tumors. Targeted massively parallel sequencing revealed several genetic alterations, most commonly in TP53 (41% mutation, 12% deletion), TSC2 (29% mutation, 6% deletion), RB1 (18% deletion), ATRX (24% mutation), MED12 (12% mutation), BRCA2 (12% deletion), CDKN2A (6% deletion) as well as FGFR3, NTRK1, and ERBB3 amplification (each 6%). Gene rearrangements (JAZF1-SUZ12; DNAJB6-PLAG1; and SFPQ-TFE3) were identified in 3 tumors. Integrating histopathologic, immunohistochemical, and genetic findings, tumors from 4 patients were consistent with malignant PEComa (1 TFE3-rearranged); 6 were classified as leiomyosarcomas; 3 showed overlapping features of PEComa and other sarcoma types (leiomyosarcoma or low-grade endometrial stromal sarcoma); and 2 were classified as sarcoma, not otherwise specified. Our findings suggest that diagnostically challenging UMTs with myomelanocytic differentiation represent a heterogenous group of neoplasms which harbor a diverse repertoire of somatic genetic alterations; these genetic alterations can aid classification.

Uterine plexiform tumourlets: multifocal and solitary cases with subsets expressing melanocytic markers

AIMS

Uterine plexiform tumourlets are traditionally regarded as microscopic epithelioid leiomyomas. They are typically solitary incidental findings, but may be multifocal (plexiform leiomyomatosis). We aim to report novel immunohistochemical and morphological findings, specifically the presence of spindled and epithelioid cell nodules, in these lesions.

METHODS AND RESULTS

Three cases of plexiform leiomyomatosis and 16 solitary plexiform tumourlets were included. Two cases of plexiform leiomyomatosis and four solitary plexiform tumourlets demonstrated spindled and epithelioid cell nodules which, in one of the former cases, formed expansile masses up to 15 mm. The nodules demonstrated mild cytological atypia and occasional mitotic activity, and they were associated with a myxoid stroma and a lymphohistiocytic infiltrate which imparted a granulomatous appearance to the microscopic lesions. The plexiform tumourlets (solitary and multifocal) consistently expressed desmin, smooth muscle actin, ER and PR, and they commonly co-expressed melanocytic and perivascular epithelioid cell (PEC) markers HMB45, MiTF and cathepsin K. The spindled and epithelioid cell nodules were generally negative for myoid markers and hormone receptors, but expressed p16, cyclin D1 and TFE3. All lesions tested were negative for cytokeratin, S100, melanA, inhibin, EMA, ALK and BCOR; fluorescence in-situ hybridisation was negative for ALK, TFE3 and BCOR rearrangements in one of the larger spindled and epithelioid cell nodules.

CONCLUSIONS

Plexiform tumourlets commonly co-express myoid and melanocytic markers and may represent part of the spectrum of gynaecological PEC-related lesions. Some cases are associated with spindled and epithelioid cell nodules that could potentially mimic other uterine myxoid neoplasms.

Perivascular epithelioid cell tumors (PEComa) of the gynecologic tract

PEComas of the female genital tract are rare mesenchymal neoplasms that are most common in the uterus, but also may occur in other gynecologic locations. As they morphologically and immunohistochemically resemble smooth muscle tumors, distinction between the two entities is often challenging, and may be aided by molecular analysis. Thus far, two distinct molecular groups-classic PEComas with TSC mutations and TFE3-translocation associated PEComas with TFE3 fusions have been described. Recognition of the first group is imperative as these patients may benefit from targeted therapy with mTOR inhibitors, if malignant. This review will focus on recognition of the morphologic and immunophenotypic features of PEComas, as well as the role of molecular testing in their diagnosis and treatment, analysis of the different algorithms to predict behavior, and differential diagnosis.

Uterine PEComas: A Morphologic, Immunohistochemical, and Molecular Analysis of 32 Tumors

Uterine perivascular epithelioid cell tumors (PEComas) are rare neoplasms that may show overlapping morphology and immunohistochemistry with uterine smooth muscle tumors. In this study, we evaluated the morphologic, immunohistochemical, and molecular features of 32 PEComas, including 11 with aggressive behavior. Two distinct morphologies were observed: classic (n=30) and those with a lymphangioleiomyomatosis appearance (n=2). In the former, patients ranged from 32 to 77 (mean: 51) years and 13% had tuberous sclerosis. Tumors ranged from 0.2 to 17 (mean: 5.5) cm with 77% arising in the corpus. Epithelioid cells were present in 100% and a spindled component was seen in 37%. Nuclear atypia was low (53%), intermediate (17%), or high (30%). Mitoses ranged from 0 to 36 (mean: 6) and 0 to 133 (mean: 19) per 10 and 50 high-power fields, with atypical mitoses present in 30%. Thin and delicate vessels were noted in 100%, clear/eosinophilic and granular cytoplasm in 93%, stromal hyalinization in 73%, necrosis in 30%, and lymphovascular invasion in 10%. All tumors were positive for HMB-45, cathepsin K, and at least one muscle marker, with most expressing melan-A (77%) and/or MiTF (79%). A PSF-TFE3 fusion was identified in one while another showed a RAD51B-OPHN1 fusion. Follow-up ranged from 2 to 175 (mean: 41) months, with 63% of patients alive and well, 20% dead of disease, 13% alive with disease, and 3% dead from other causes. In the latter group (n=2), patients were 39 and 49 years old, one had tuberous sclerosis, while the other had pulmonary lymphangioleiomyomatosis. Both tumors expressed HMB-45, cathepsin K, and muscle markers, but lacked TFE3 and RAD51B rearrangements. The 2 patients are currently alive and well. Application of gynecologic-specific criteria (≥4 features required for malignancy: size ≥5 cm, high-grade atypia, mitoses >1/50 high-power fields, necrosis, and lymphovascular invasion) for predicting outcome misclassified 36% (4/11) of aggressive tumors; thus, a modified algorithm with a threshold of 3 of these features is recommended to classify a PEComa as malignant.

[A suspected carcinoma finding in the uterus]

Epithelioid tumor cells of a uterine perivascular epithelioid cell tumor (PEComa) may mimic carcinoma cells in an endometrial sampling (pitfall). Immunohistochemistry (HMB45 positive, keratin negative) helps in the differential diagnosis.

The Usefulness of Immunohistochemistry in the Differential Diagnosis of Lesions Originating from the Myometrium

Uterine leiomyomas (LMs), currently the most common gynecological complaint around the world, are a serious medical, social and economic problem. Accurate diagnosis is the necessary prerequisite of the diagnostic-therapeutic process. Statistically, mistakes may occur more often in case of disease entities with high prevalence rates. Histopathology, based on increasingly advanced immunohistochemistry methods, is routinely used in the diagnosis of neoplastic diseases. Markers of the highest sensitivity and specificity profiles are used in the process. As far as LMs are concerned, the crux of the matter is to identify patients with seemingly benign lesions which turn out to be suspicious (e.g., atypical LM) or malignant (e.g., leiomyosarcoma (LMS)), which is not uncommon. In this study, we present the current state of knowledge about the use of immunohistochemical markers in the differential diagnosis of LM, atypical LM, smooth muscle tumors of uncertain malignant potential (STUMP), and LMS, as well as their clinical predictive value.

Beyond Smooth Muscle-Other Mesenchymal Neoplasms of the Uterus

Mesenchymal tumors of the uterus comprise a heterogeneous group of neoplasms of varied biologic potential. In addition to being host to several anatomically unique entities, the uterus may contain mesenchymal neoplasms typically found elsewhere in the body. Although smooth muscle neoplasms are common, other mesenchymal neoplasms in this location are relatively rare. Many of these neoplasms exhibit morphologic overlap. In addition to a careful histomorphologic review, definitive classification frequently depends on the judicious application of ancillary immunohistochemical and molecular testing. The intent of this review is to offer a basic approach to the classification of primary uterine mesenchymal neoplasms.

Perivascular Epithelioid Cell Tumor (PEComa) of the Uterine Cervix: A Case Report of a 43-Yr-Old Woman With Abnormal Uterine Bleeding Treated With Hysterectomy

Perivascular epithelioid cell tumor (PEComas) are a group of ubiquitous neoplasms described in different organs that share distinctive morphologic, immunohistochemical, ultrastructural, and genetic features. They have been reported in several organs such as the uterus, lung, kidney, liver, small and large bowel, and prostate. To the best of our knowledge, only 8 cervical PEComa cases have been described. We report the case of a 43-yr-old woman who presented with abnormal uterine bleeding. Clinical diagnosis of a malignant cervical lesion followed an excision, histopathologically evaluated as PEComa. The hysterectomy specimen confirmed the diagnosis by strong HMB-45 positivity, weak S100 positivity, and focal, moderate cytoplasmic TTF-1 positivity, and negative melan A, SMA, desmin, vimentin, cytokeratins, CD1a and other markers. The patient was negative for tuberous sclerosis complex, did not receive additional therapy, and 3 yr later is disease free. Cervical PEComas are very rare tumors but have to be considered in the differential diagnosis of cervical lesions exhibiting unusual cytologic and immunohistochemical characteristics.

Uterine Mesenchymal Tumors: Hereditary Aspects

The topic of hereditary gynecologic malignancies readily evokes associations between Lynch syndrome and endometrial adenocarcinoma, or between BRCA mutations and tubo-ovarian serous carcinoma, but other familial associations are less well-known. Two hereditary syndromes are known to be related to uterine mesenchymal tumors: hereditary leiomyomatosis and renal cell carcinoma syndrome and the tuberous sclerosis complex. In the following review, we describe the current literature on these syndromes, summarizing their clinical, morphologic, immunophenotypic, and genetic data. It is possible that the surgical pathologic diagnosis is the first indication of a familial syndrome, thus emphasizing the importance of a pathologist's familiarity with these potentially suggestive lesions.

Giant Perivascular Epithelioid Cell Tumor of the Orbit: A Clinicopathological Analysis and Review of the Literature

Aim

To describe and review the clinical, radiological, and histopathological characteristics of an orbital perivascular epithelioid cell tumor (PEComa).

Methods

A systematic review of clinical records, radiological investigations, microscopic features, and immunohistochemical characteristics was done.

Results

A 9-year-old female child presented with a year-long history of a large orbital mass associated with painless, progressive proptosis of the right eye. Radiologically, a well-defined orbital mass was seen with no intracranial extension. Excision was performed and histopathological examination showed uniform epithelioid cells in nests separated by thin fibrovascular septae. The tumor cells stained positively for Human Melanoma Black-45, but neg-atively for desmin, S-100, smooth muscle actin, MyoD1, microphthalmia-associated transcription factor, vimentin, CD10, CD31, and CD34 with a low proliferation index of 5-7%. Based on the tumor's morphological and immuno-histochemical characteristics, a diagnosis of giant orbital PEComa was made. No recurrence was seen at the last follow-up.

Conclusions

PEComas are uncommon mesenchymal neoplasms that have typical histological features, with an immunohistochemical profile of negativity for epithelial markers and positivity for melanocytic markers. For benign PEComas, complete excision is advised. However, since PEComas elsewhere in the body have been known to be malignant, a close follow-up of such cases is recommended.

Criteria for Risk Stratification of Vulvar and Vaginal Smooth Muscle Tumors: An Evaluation of 71 Cases Comparing Proposed Classification Systems

Accurate risk stratification of smooth muscle tumors (SMTs) is essential for appropriate patient management. Yet, the rarity of SMTs of the vagina and vulva makes development of a prognostically meaningful classification system challenging. While 2 classification methods for vulvar SMTs and 1 for vaginal SMTs have been proposed, it is our experience that many pathologists tend to apply criteria for uterine SMTs when evaluating vulvovaginal tumors. We retrospectively reviewed a large cohort of vulvovaginal SMTs with clinical follow-up and evaluated which method most accurately classified tumors according to patient outcome. A total of 71 tumors, 53 vaginal (75%) and 18 vulvar (25%), from 71 patients were identified. All tumors were centrally examined for degree of cytologic atypia, morphology (spindled, epithelioid, myxoid), mitotic index per 10 high power fields, atypical mitotic figures, tumor cell necrosis, ischemic necrosis, tumor interface (circumscribed or infiltrative) and margin status. Clinical features were recorded for each patient. Follow-up was available for 63 patients (89%), and ranged from 1 to 234 months (median: 64 mo). While site-specific and uterine criteria showed equally excellent sensitivity in classifying smooth muscle neoplasms as leiomyosarcoma according to patient outcome, uterine criteria showed improved specificity relatively to site-specific methods in classifying tumors as nonsarcoma according to patient outcome. We recommend that uterine SMT criteria and nomenclature be adopted for evaluation and classification of vulvovaginal SMTs.

Primary malignant perivascular epithelioid cell neoplasm (PEComa) of the bone mimicking granular cell tumor in core biopsy: A case report and literature review

The present study investigated the case of a 46-year-old female with primary malignant perivascular epithelioid cell neoplasm (PEComa) of the femur. The patient presented with a 5-month history of right distal thigh pain following trauma. Radiographs of the right distal femur revealed a mixed lytic and sclerotic lesion with subtle areas of cortical destruction and soft tissue extension, consistent with an aggressive tumor. A core biopsy revealed an epithelioid tumor with granular cell features, but a definitive diagnosis could not be made. Due to the aggressive features on radiologic evaluation, the patient underwent a resection of the distal femur and reconstruction with a distal femoral megaprosthesis and hinged knee replacement. The post-resection pathology led to a final diagnosis of primary bone PEComa, with histologic features including epithelioid, granular cell and spindled cell morphologies and biphasic immunoreactivity for melanocytic and smooth muscle markers. The large tumor size (>5 cm), rapid mitotic rate, infiltrative growth pattern, high nuclear grade and cellularity, and the presence of necrosis rendered this a malignant PEComa. The present study discussed the case, including radiographic (radiographs, magnetic resonance imaging and positron emission tomography scans) and histologic appearance and a literature review.

Pigmented perivascular epithelioid cell tumor of the skin: first case report

The authors present a first case of pigmented perivascular epithelioid cell tumor (PEComa) of the skin, which was misdiagnosed histopathologically as metastatic melanoma. PEComa are exceedingly rare neoplasms, and only a few cases have been reported in kidney, liver, and pelvis. Herein, we describe this very rare entity in the subcutaneous tissue of the flank with very similar if not identical morphology of renal clear cell carcinoma. Because of the presence of focal melanin pigmentation and strong positivity for HMB-45, the lesion was mistaken for metastatic melanoma. To the best of authors' knowledge, this is the first case of cutaneous PEComa with melanin pigmentation. Awareness about occurrence of the lesion in the subcutaneous tissue and its unique immunoprofile would be helpful to reach correct diagnosis and to distinguish this lesion from melanoma or metastatic renal clear cell carcinoma.

Molecular targeted therapy in gynaecologic malignancies: primer for radiologists

The identification of characteristic genetic alteration in gynaecological malignancies has opened the door for molecular targeted therapy. The purpose of this review is to provide a primer for the radiologist on these agents with emphasis on the role of imaging in treatment response assessment and drug toxicities. The use of targeted therapy in gynaecological malignancies will likely increase in the future and make the role of the radiologist critical in response assessment and detection of toxicities.

Gynecologic Manifestations of Less Commonly Encountered Hereditary Syndromes

This review covers gynecologic manifestations that may occur in rare hereditary syndromes. Recent advances in disorders, such as hereditary leiomyomatosis, renal cell carcinoma syndrome and tuberous sclerosis complex, are discussed as well as lesions that occur in von Hippel-Lindau syndrome, nevoid basal cell carcinoma syndrome, Cowden syndrome, Ollier disease/Maffucci syndrome, and Carney complex. Characteristic clinicopathologic features of each of these syndromes are discussed with an emphasis on the key features that enable pathologists to identify patients at highest risk for these diseases.

Cutaneous perivascular epithelioid cell tumors: A review on an infrequent neoplasm

“Perivascular epithelioid cutaneous” cell tumors (PEComa) are a family of mesenchymal tumors with shared microscopic and immunohistochemical properties: They exhibit both smooth muscle cell and melanocytic differentiation. Non-neoplastic counterpart of PEComa’s cells are unknown, as well as the relationship between extracutaneous PEComa and primary cutaneous ones. We will review the clinical setting, histopathologic features, chromosomal abnormalities, differential diagnosis and treatment options for cutaneous PEComa.

Imaging Features of Uncommon Gynecologic Cancers

OBJECTIVE

The role of imaging in patients with suspected gynecologic malignancies is to provide an accurate diagnosis to achieve the best and most tailored treatment plan. Uncommon cancers pose a distinct challenge, because current knowledge of these diseases is still limited. Our purpose is to highlight the role of cross-sectional imaging techniques, including ultrasound, CT, MRI, and PET/CT, in the diagnosis and pretreatment stratification of patients with rare gynecologic cancers.

CONCLUSION

This review shows the relevance of imaging findings for diagnosis, staging, and treatment planning in patients with uncommon uterine, cervical, vaginal, vulvar, and ovarian cancers.

Practical issues in uterine pathology from banal to bewildering: the remarkable spectrum of smooth muscle neoplasia

Among mesenchymal tumors of the uterus, smooth muscle neoplasms are most common. The wide morphologic spectrum, especially within the category of leiomyomas, is responsible for diagnostic problems more frequently with leiomyosarcoma (including mitotically active, apoplectic, and leiomyoma with bizarre nuclei) but also with endometrial stromal tumors. In the former scenario, clinical information, gross appearance as well as strict utilization of morphologic criteria including cytologic atypia, mitotic activity, and tumor cell necrosis are clues in establishing the correct diagnosis. It is important to keep in mind that mitotic rate thresholds vary for the different subtypes of leiomyosarcoma. Of note, p16 should be used with caution in supporting a diagnosis of leiomyosarcoma as it is often positive in leiomyomas with bizarre nuclei and leiomyomas with apoplectic change (in the latter most frequently and more intense near areas of necrosis). MED12 mutations have also a very limited role in this differential diagnosis. Endometrial stromal tumors are by far, less common than smooth muscle tumors, but can be confused with leiomyosarcomas if they are associated with an undifferentiated uterine sarcoma and the low-grade component is overlooked or they have a myxoid/fibroblastic morphology. The differential diagnosis may be confounded if the latter is associated with a high-grade endometrial stromal sarcoma. It is important to highlight that CD10 is not a reliable marker in these differentials and should be used as a part of a panel of antibodies that also includes desmin and h-caldesmon. Two other recently categorized tumors in the uterus that merit special mention are PEComa and inflammatory myofibroblastic tumor as they enter in the differential diagnosis of smooth muscle tumors. PEComa may be part of the tuberous sclerosis syndrome and may show either a predominantly epithelioid or spindle morphology or combination thereof. Rarely, it may contain melanin pigment. There is variable positivity for HMB-45, MelanA, MiTF, and CathepsinK, and some tumors have been shown to express TFE-3 especially when associated with "clear cell" morphology. Patients with adverse outcome have tumors with ≥2 of the following features: ≥5 cm, infiltration, high-grade cytologic features, mitotic rate ≥1/50 high-power fields, necrosis, or lymphovascular invasion. Inflammatory myofibroblastic tumor is important to recognize as it often mimics myxoid smooth muscle tumors, either benign or malignant. The presence of an associated lymphoplasmacytic infiltrate should alert to that possibility and ALK studies (immunostain or FISH) are helpful in establishing this diagnosis. These tumors can behave in a malignant manner if large, associated with abundant myxoid change, brisk mitotic rate or show tumor cell necrosis.

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

Background

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

Case presentation

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

Conclusion

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

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

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

Incidental Pelvic and Para-aortic Lymph Node Lymphangioleiomyomatosis Detected During Surgical Staging of Pelvic Cancer in Women Without Symptomatic Pulmonary Lymphangioleiomyomatosis or Tuberous Sclerosis Complex

Extrapulmonary lymphangioleiomyomatosis (LAM) is a rare neoplasm of spindle cells exhibiting melanocytic and myoid differentiation that arises as a mass in the mediastinum, retroperitoneum, uterine wall, and/or intraperitoneal lymph nodes. Many patients also have pulmonary LAM, tuberous sclerosis complex (TSC), and/or other neoplasms of the perivascular epithelioid cell tumor family. This study reports 26 patients with clinically occult LAM involving pelvic/para-aortic lymph nodes removed from women undergoing surgical staging of a uterine (17), ovarian (5), cervical (3), or urinary bladder (1) neoplasm. None of the patients exhibited symptoms of pulmonary LAM, and the median patient age (56 y) was older than what would be expected for patients presenting with pulmonary LAM. Only 2/26 patients had TSC. Four patients also had uterine LAM. One of these 4 had uterine perivascular epithelioid cell tumor, and 1 had vaginal angiomyolipoma. In all 26 patients the lymph node LAM was grossly occult, measured 3.5 mm on average (1 to 19 mm), and involved either a single lymph node (12/26) or multiple lymph nodes (14/26). HMB45 was positive in 24/25 cases, mostly in a focal or patchy distribution. Other melanocytic markers included MiTF (12/14) and MelanA (2/12). Myoid markers included smooth muscle actin (23/23) and desmin (15/16), mostly in a diffuse distribution. Estrogen receptor was positive in all cases tested, as was D240 expression in the lymphatic endothelium lining the spindle cell bundles. Concurrent findings in the involved lymph nodes included metastatic carcinoma (3/26), endosalpingiosis (3/26), and reactive lymphoid hyperplasia (13/26). This study demonstrates that clinically occult lymph node LAM can be detected during surgical staging of pelvic cancer and is not commonly associated with pulmonary LAM or TSC, although these patients should still be formally evaluated for both of these diseases.

PEComa: morphology and genetics of a complex tumor family

Perivascular epithelioid cell tumors, or PEComas, are mesenchymal neoplasms composed of histologically and immunohistochemically distinctive epithelioid or spindle cells, which are immunoreactive for both smooth muscle and melanocytic markers. The cells in PEComas are typically arranged around blood vessels and appear to form the vessel wall, often infiltrating the smooth muscle of small- to medium-sized vessels. Periluminal cells are usually epithelioid and the more peripheral cells are spindle shaped. The cells have small, round to oval nuclei, sometimes with focal nuclear atypia, and clear to eosinophilic cytoplasm, and no counterpart normal cell has been identified. The PEComa "family" now includes angiomyolipoma, pulmonary clear cell "sugar" tumor and lymphangioleiomyomatosis, primary extrapulmonary sugar tumor, clear cell myomelanocytic tumor of the falciform ligament/ligamentum teres, abdominopelvic sarcoma of perivascular epithelioid cells, and other tumors with similar features at various sites that are simply termed PEComa. Some PEComas occur in patients with tuberous sclerosis complex and share the genetic abnormalities. There is a behavioral spectrum from benign to frankly malignant, and histologic criteria have been proposed for assessing malignant potential. The differential diagnosis can include carcinomas, smooth muscle tumors, other clear cell neoplasms, and adipocytic tumors. PEComas constitute a genetically diverse group that includes neoplasms harboring TFE3 gene rearrangements and those with TSC2 mutations, indicating alternative tumorigenic pathways. Recent advances in therapy of malignant PEComas relate to increased knowledge of specific genetic changes and their effects on metabolic pathways that are susceptible to specific interventions. We review PEComas, emphasizing the diagnostic spectrum and recent immunohistochemical and genetic findings.