Late pulmonary metastasis in uterine PEComa

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

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

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.

Primary retroperitoneal PEComa: an incidental finding

Perivascular epithelioid cell neoplasm (PEComa) is a rare type of tumour, and primary retroperitoneal PEComa is rarer still. Although pulmonary lymphangioleiomyomatosis (LAM), angiomyolipomas and clear cell 'sugar' tumours of the lung are well described, relatively little is known about other members of the PEComa family. We describe a case of an asymptomatic retroperitoneal PEComa, lymphangioleiomyoma type, which appeared in a previously healthy middle-aged woman as an incidental finding, in a CT scan performed in the context of spontaneous pneumothorax. The patient underwent surgical excision of the tumour and the histopathological and immunohistochemical analysis of the surgical specimen made the definitive diagnosis. Although rare, reports of isolated retroperitoneal lymphangioleiomyoma and primary retroperitoneal PEComas NOS (not otherwise specified) are described in the literature, normally associated with pulmonary LAM. The patient's pulmonary imaging was normal. Short-term re-examination did not detect any recurrence. We also provide a literature review of this rare group of tumours.

Recurrent YAP1-TFE3 Gene Fusions in Clear Cell Stromal Tumor of the Lung

Clear cell (hemangioblastoma-like) stromal tumor of the lung (CCST-L) is a recently described distinctive rare pulmonary neoplasm of unknown histogenesis and molecular pathogenesis. Only 7 cases have been reported in 2 recent studies, although additional cases might have been reported under the heading of extraneural pulmonary hemangioblastoma. We herein describe 4 CCST-L cases, 3 of them harboring a YAP1-TFE3 fusion. The fusion-positive tumors occurred in 3 women, aged 29, 56, and 69 years. All presented with solitary lung nodules measuring 2.3 to 9.5 cm. Histologically, all tumors showed similar features being composed of relatively uniform medium-sized epithelioid to ovoid cells with clear cytoplasm and small round monomorphic nuclei. Scattered larger cells with enlarged hyperchromatic nuclei and marked pleomorphism were noted in 2 cases. The tumors were associated with a hypervascularized stroma with variable but essentially subtle resemblance to capillary hemangioblastoma and perivascular epithelioid cell tumor (PEComa). Immunohistochemistry was negative for all lineage-specific markers. Targeted RNA sequencing showed a YAP1-TFE3 fusion in 3 of 4 cases. All 3 tumors showed homogeneous nuclear TFE3 immunoreactivity. Two patients were disease free at 36 and 12 months. The third patient had biopsy-proven synchronous renal and hepatic metastases, but extended follow-up is not available (recent case). The fourth case lacking the fusion affected a 66-year-old woman and showed subtle histologic differences from the fusion-positive cases, but had comparable TFE3 immunoreactivity. CCST-L represents a distinctive entity unrelated to hemangioblastoma and likely driven by recurrent YAP1-TFE3 fusions in most cases. The relationship of our cases to the recently reported "hemangioblastoma-like" CCST-L remains to be determined. Analysis of larger series is paramount to delineate the morphologic spectrum and biological behavior of this poorly characterized entity.

A successful case of complete surgical resection via left upper and right lower lobectomy for bilateral lung metastases of a perivascular epithelioid cell tumor in the colon: a case report

Background

Perivascular epithelioid cell tumors (PEComas) are rare mesenchymal neoplasms with malignant potential. No effective treatment other than surgical resection has been established for lung metastases of PEComas. We describe a patient who underwent complete surgical resection via bilateral lobectomy involving a two-step procedure for lung metastases 8 years after undergoing radical surgery for a colonic PEComa.

Case presentation

A 53-year-old woman underwent partial colectomy for a PEComa in the transverse colon 8 years ago. She presented with an abnormal chest shadow during a health examination. Chest computed tomography (CT) revealed a solid nodule 2 cm in diameter located centrally in the right lower lobe and a solid nodule 3 cm in diameter located centrally in the left upper lobe. Positron emission tomography revealed 18F-fluorodeoxyglucose uptake in these nodules. These nodules were suspected to be metastatic tumors of the colonic PEComa and were considered for complete surgical resection. Segmentectomy could not be performed because of the anatomical location of the tumors straddling the segments; therefore, bilateral lobectomy was required for complete surgical resection. Therefore, we performed two-step lobectomy safely with the expectation of pulmonary function recovery. Microscopically, the tumors were diagnosed as lung metastases of the PEComa. One year after the last surgery, no recurrence was detected, and the patient’s pulmonary function improved.

Conclusions

This case indicates that even if multiple lung metastases of a PEComa require bilateral lobectomy, complete resection with a two-step surgery may be considered.

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

Simple Summary

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

Abstract

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

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.

Perivascular Epithelioid Cell Tumor of the Urinary Bladder: A Systematic Review

Perivascular epithelioid cell tumor (PEComa) of the urinary bladder is a rare neoplasm showing distinct melanocytic and smooth muscle differentiation. We aimed to review the clinicopathologic features of bladder PEComa using all the available cases in the literature, along with 2 new cases from our database. The patients included 15 females and 15 males with a mean age of 39.2 ± 15.3 years. Painless hematuria was the most common clinical presentation. The tumors were usually well circumscribed with a mean tumor size of 4.4 ± 2.7 cm. Bladder PEComas demonstrated nests, trabeculae, or sheets of epithelioid cells with intermixed spindled cells and numerous thin-walled vessels. Immunohistochemical studies showed that the tumors were positive for HMB45 (27/27), cathepsin (4/4), SMA (20/22), and caldesmon (3/3) and were negative for pan cytokeratin (0/18) and EMA (0/4). Molecular studies revealed that PEComa was associated with the TFE3 (n = 3) and EWSR1 (n = 1) gene rearrangements. Treatment included partial cystectomy (n = 18), transurethral resection (n = 8), and radical cystectomy (n = 4). Twenty patients had no evidence of disease during a mean follow-up time of 19.4 ± 17.2 months. Two patients had recurrence, and 1 patient died of metastatic disease. In conclusion, bladder PEComas demonstrate distinct morphologic and immunohistochemical features. Although most tumors follow a benign course, a small subset may develop metastasis and cause death.

Perivascular Epithelioid Cell Tumor (Pecoma) in the Transverse Colon of an Adolescent: A Case Report

Perivascular epithelioid cell tumor (PEComa) is defined as a very rare mesenchymal tumor of histologically and immuno-histochemically distinctive perivascular epithelioid cells. PEComa in the colon is very rare, with only a few reported cases so far. Because of its rarity, the clinical features and biological behavior of PEComa in the colon have yet to be established. A 16-year-old female patient with PEComa in the transverse colon was referred to our hospital for rectal bleeding. Laboratory data showed a hemoglobin level of 6.6 g/dL, WBC of 8,800/mm3, and platelet count of 191,000/mm3. Colonoscopy, barium enema, and abdominal computed tomography revealed a 2-cm, smooth-surfaced, round tumor with focal ulceration in the proximal transverse colon. The patient complained of abdominal pain one day after endoscopic polypectomy. She underwent a segmental resection for a perforated transverse colon. Immunohistochemically, the tumor cells showed strong diffuse positivity for HMB-45 while they were negative for c-kit, smooth muscle actin, cytokeratin, S-100, vimentin, desmin, chromogranin, synaptophysin, EMA, and CD-34. The diagnosis of PEComa was based on histological and immunohistochemical staining. The patient did not receive any adjuvant therapy and was discharged on postoperative day 11 without complications. Whole-body fluorine-18 fluorodeoxyglucose fusion positron emission tomography performed 2 months after surgery showed no signs of recurrence or metastasis. There was also no recurrence or metastasis at 24 months' follow-up.

Predicting the Behavior of Perivascular Epithelioid Cell Tumors of the Uterine Corpus

Perivascular epithelioid cell tumors (PEComas) are rare neoplasms that share phenotypic features with angiomyolipomas, clear cell sugar tumors, and lymphangioleiomyomatosis. They presumably represent the neoplastic counterpart of a yet-unidentified perivascular epithelioid cell that expresses smooth muscle and melanocytic immunomarkers. The uterus is the second most common site of origin for perivascular epithelioid cell tumors, after the retroperitoneum. Although most uterine perivascular epithelioid cell tumors are clinically benign and can be cured by a complete surgical excision, there is a subset characterized by both local and distant dissemination. Unfortunately, no single histopathologic or immunohistochemical parameter can accurately predict the clinical behavior of these tumors, which is why the 2012 World Health Organization classification of tumors of the female reproductive organs suggests the use of several criteria to predict the risk of aggressive clinical behavior. Here we review those perivascular epithelioid cell tumors of the uterine corpus with aggressive clinical behavior reported in the literature, and we discuss their most relevant clinical and histopathologic features.

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

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

Angiomyolipoma and Malignant PEComa: Discussion of Two Rare Adrenal Tumors

Angiomyolipoma and PEComa are rare tumors descending from perivascular epithelial cells (PECs), with distinctive IHC, morphological, and ultrastructural features. The kidney is the most frequent site of origin, but not the only one; however, adrenal gland angiomyolipomas are extremely rare. We describe two cases being found in the adrenal glands. Given the paucity of literature on the subject, more information on this disease is necessary for diagnosis and treatment. Here, we describe two complete case reports, from presentation to treatment and follow-up, along with imaging and microscopic pathology samples, and provide a comprehensive review as to the history and current literature available regarding these extremely rare tumors.

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.

Expression of CD44 and CD29 by PEComa cells suggests their possible origin of mesenchymal stem cells

BACKGROUND

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. The perivascular epithelioid cell (PEC) co-expresses melanocytic and muscle markers. Since no normal counterpart to the PEC has ever been identified in any normal tissue, the cell origin of these tumors is still uncertain. Although, several hypotheses have recently been advanced to explain the histogenesis of PEComa, it remains unclear.

METHODS

The aim of this study was to discuss whether differential expression of stem cell-associated proteins could be used to aid in determining the histogenesis of PEComa. For this purpose, we detected the immunoexpression of 5 kinds of stem cell markers on PEComas, including CD29, CD44, CD133, ALDH1, and nestin. In addition to observed histopathologic morphology, we also performed PEComa relevant clinical diagnostic markers (HMB-45, SMA, melan-A, Desmin, Ki-67, S-100 and TFE3) to identify whether they belonged to PEComas.

RESULTS

Our study included 13 PEComa samples, and we obtained positive immunoexpression results as follows: CD29 (13/13), CD44 (8/13), ALDH1 (10/13), nestin (1/13), and CD133 (0/13).

CONCLUSIONS

Since CD44 and CD29 are surface proteins associated with MSCs, these results suggest that PEComa might arise from MSCs. However, whether MSCs are the origin of PEComa needs to be further explored in the future.

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.

Perivascular epithelioid cell neoplasm (PEComa) of the uterus: A systematic review

BACKGROUND

Perivascular epithelioid cell neoplasm (PEComa) is a rare mesenchymal tumor. Gynecological PEComas account for just over one-fourth of the overall PEComa cases reported in the literature. Surgery is the most recommended primary treatment while adjuvant therapy is generally reserved for high-risk cases. However, the best management of this neoplasia has not been well established, primarily because of the paucity of cases described to date.

OBJECTIVES

The aim of this systematic review is to summarize what is known thus far regarding the etiopathogenesis, clinical and pathologic features of PEComas, focusing also on the most valid treatment options for uterine cases.

DATA SOURCES

Pubmed articles on PEComas published in various journals over the past 70 years were analyzed.

CONCLUSIONS AND KEY FINDINGS

Although the optimal treatment of gynecological PEComas is controversial, surgical resection remains the cornerstone. The use of adjuvant treatment is warranted in high risk patients to increase disease control. A multidisciplinary approach should be key in treatment decision-making regarding gynecological PEComas.

Perivascular epithelioid tumours (PEComas) of the gynaecological tract

Perivascular epithelioid tumours (PEComas) of the gynaecological tract are rare tumours which were first recognised and diagnosed within the last 20 years. They represent a unique diagnostic challenge with regard to their accurate and reproducible distinction from more common entities such as smooth muscle tumours of the uterine corpus. In this review article, we trace the development of the concept of the PEComa tumour family, highlight what is known about extra-gynaecological tract PEComa at an immunohistochemical, molecular and therapeutic level and then present a summary of all reported cases of gynaecological tract PEComa to date. In the summary, we highlight rare subtypes of gynaecological tract PEComa and compare the performances of extant prognostic classification systems for malignancy in these tumours.

Uterine perivascular epithelioid cell tumour

Uterine perivascular epithelioid cell tumour (PEComa) is a rare disease and its biological behaviour remains unclear. This paper describes the clinical, histological and immunohistochemical features of three cases of uterine PEComa to add to our limited knowledge of the biological characteristics of these tumours. Histologically, the tumours were characterised by an epithelioid arrangement of tumour cells with abundant clear to eosinophilic, pale, granular cytoplasm. Immunohistochemically, the tumours were uniformly positive for HMB45, desmin and progesterone receptor; they were uniformly negative for h-caldesmon, α-smooth muscle actin, CD34, epithelial membrane antigen (EMA) and oestrogen receptor (ER). Review of the literature suggests that the size of the primary tumour (> 5 cm in diameter) and high mitotic rates are two important indicators of recurrence. Treatment options are limited though new mTOR inhibitors show some promise in early reports.

Multi-slice computed tomography manifestations of hepatic epithelioid angiomyolipoma

AIM: To explore the characteristics of multi-slice computed tomography (CT) manifestations of hepatic epithelioid angiomyolipoma (HEA), improve the rate of accurate diagnosis, and reduce the misdiagnostic rate.

METHODS: The multi-slice CT manifestations in five patients who were diagnosed with HEA definitely by postoperative pathological examination were analysed retrospectively. Three female patients and two male patients were included. Before operation, four patients received plain CT scanning and dynamic enhancement scanning, and the other patient only received enhancement scanning, with immunohistochemical analysis conducted after postoperative pathological examination. Four patients were misdiagnosed by CT, including three patients misdiagnosed with hepatic cell carcinoma and one patient with focal nodular hyperplasia.

RESULTS: Upper abdominal multi-slice spiral CT scanning and three-stage enhancement scanning were conducted in five patients with HEA before operation. HEA had certain characteristic CT manifestations: low density masses, a few relatively high-density masses or fat-density masses diffusely shown in foci, clear boundary, round or oval and large focus, and tumour size ranging from 3.1 cm × 2.5 cm to 7.0 cm × 5.2 cm. During enhancement scanning, the foci were significantly enhanced uniformly or non-uniformly during the arterial phase, while during the venous and equilibrium phases, the foci were enhanced continuously or showed obvious low-density masses. Obviously enhanced and widened vessels could be found adjacent to foci or in the central area of foci during the arterial phase.

CONCLUSION: CT manifestations of HEA have certain characteristics. Primary diagnosis can be obtained by combining CT findings with clinical data, but pathological examination is still needed for a definite diagnosis.

Uterine tumors resembling ovarian sex cord tumors

Uterine tumors resembling ovarian sex cord tumors (UTROSCT) are rare neoplasms of unknown etiology. Only 67 cases have been reported in the literature, to our knowledge, so far. The neoplasm usually occurs in middle-aged women. Most patients present with abnormal uterine bleeding and/or abdominal pain, along with an enlarged uterus or a palpable uterine mass. There is no specific imaging finding, and the diagnosis is made exclusively on histopathologic examination. A multitude of architectural patterns are described, which include plexiform cords, anastomosing trabeculae, watered-silk, microfollicle, macrofollicle, tubules, retiform, solid cellular islands, and diffuse pattern of growth. The neoplastic cells are usually small with round to ovoid nuclei, nuclear monotony, mild nuclear hyperchromasia, and inconspicuous nucleoli with scant eosinophilic cytoplasm. Nuclear grooves are rare. Mitotic figures are infrequent, and necrosis is mostly absent. This tumor depicts a diverse immunohistochemical profile with expression of sex cord, epithelial, and smooth muscle lineages markers. Sex cord markers, such as inhibin, calretinin, CD99, WT1, and MART-1; epithelial markers, such as pancytokeratin and epithelial membrane antigen; smooth muscle markers, such as smooth muscle actin, desmin, and histone deacetylase 8; and miscellaneous markers, such as CD10, estrogen receptor, progesterone receptor, S100, and CD117, are often coexpressed. Immunoexpression for calretinin and at least for one of the other sex cord markers is required to establish a diagnosis of UTROSCT. Hysterectomy with or without bilateral salpingo-oophorectomy is usually the treatment for UTROSCT. Although most UTROSCTs behave benignly, some do recur, and thus, this entity should be considered as a tumor of low malignant potential. In this review, we discuss the current knowledge on UTROSCT and its clinical relevance.

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

AIM

To evaluate the dynamic computed tomography (CT), magnetic resonance imaging (MRI), and clinicopathological characteristics of perivascular epithelioid cell tumours (PEComas), thus improving the diagnosis of the tumour.

MATERIALS AND METHODS

A retrospective analysis was undertaken of the dynamic CT, MRI, and clinicopathological characteristics of 32 PEComas diagnosed at histopathology during the period 1 January 2005 to 1 March 2012 at two hospitals.

RESULTS

The age of the patients ranged from 14-80 years (mean 43.3 years). There were more women in this group (19/32). Solitary tumours were identified in kidney (n = 16), liver (n = 7), gynaecological organs (n = 2), retroperitoneal soft tissue (n = 2), lung (n = 2), palate (n = 1), left groin (n = 1). One patient had multiple tumours in the liver, kidney, and retroperitoneal soft tissue. Dynamic CT (32 cases) and MRI (15 cases) demonstrated tumours that were of low density or hypointense on T1-weighted imaging (WI) and hyperintense on T2WI; some were isodense with fat (CT: 10/32; MRI: 6/15). The tumours usually had well-defined borders and were of a regular shape (CT: 26/32; MRI: 12/15). Tumour diameters ranged from 1.5-18 cm (mean 5.1 cm). Most tumours (CT: 21/32, MRI: 10/15) enhanced heterogeneously and significantly on arterial and venous phases. Tumours appeared slightly hypodense on delayed CT imaging, although some (6/32) had delayed enhancement. The expression rate of HMB-45 (human melanoma black monoclonal antibody) was 100% (32/32). Histological classification in 22 cases (22/32) was epithelioid angiomyolipoma (AML), three (3/32) were clear cell "sugar" tumours (CCSTs), two (2/32) were lymphangioleiomyomatosis (LAM), and two (2/32) were clear cell myomelanocytic tumours of the falciform ligament/ligamentum teres (CCMMT). Three tumours did not have a specific classification.

CONCLUSION

Knowledge of dynamic CT, MRI, and clinicopathological characteristics could help improve the diagnosis of PEComa.

Hepatic perivascular epithelioid cell tumor (PEComa): dynamic CT, MRI, ultrasonography, and pathologic features--analysis of 7 cases and review of the literature

OBJECTIVE

To evaluate the dynamic CT, MRI, ultrasonography, and pathologic features of hepatic perivascular epithelioid cell tumor (PEComa), improving the understanding and diagnosis of the tumor.

METHODS

A retrospective analysis of CT, MRI, ultrasonography, and pathologic features of 7 hepatic PEComas diagnosed by pathology during 1st January 2005 to 1st September 2011 in our hospital.

RESULTS

The performance of dynamic CT, MRI, and ultrasonography revealed that lesions were regular masses with well-defined borders, the maximum diameters were 2.5-8.5 cm (mean = 4 cm), density was homogeneous, contrast-enhanced CT and MRI showed the lesions were significantly and heterogeneously enhanced on arterial phase, less enhanced on portal venous phase, and slightly hypodense on delayed phase. One patient had multiple hepatic lesions and had delayed enhancement. There were no backgrounds of hepatitis and cirrhosis, enlarged lymph nodes, or distant metastases. Pathology showed the gross appearance of the tumor was smooth. Tumor cells were round or polygonal, with clear boundaries and clear membranes, and had abundant translucent cytoplasm. Nuclei were round, with medium size. Tumor cells were epithelial-like cells and arranged in dense sheets. Immunohistochemistry showed that most of them were positive in HMB45 and MelanA, S-100, SMA, while negative in CgA, Syn, CK, CD117, CD10, and CD34.

CONCLUSIONS

Dynamic CT, MRI, ultrasonography, and pathology of PEComa had some characteristics of benign tumor's performance. Enhanced scan showed PEComa quickly enhanced on arterial phase and enhanced less on portal venous phase. Knowing these characteristics could help to improve the understanding and diagnosis of hepatic PEComa.

Cardiac Epithelioid PEComa: Report of Two Cases and Review of the Literature

Cardiac PEComa is very rare. We reported two cases of epithelioid PEComas, one in an adult and one in a 2-year-old child. Both tumors were composed of sheets of epithelioid cells with coagulation necrosis. In addition, the adult case showed marked nuclear atypia and high mitotic activity with atypical mitosis and the pediatric case showed unusual clear cell features. Immunohistochemically, both tumors were positive for HMB-45 and SMA and negative for S100 and cytokeratin. Electron microscopy was performed in the pediatric case and showed premelanosomes. The adult patient developed extensive metastasis indicating malignant behavior. Prior to the two cases, only 5 other cases of cardiac PEComa were reported and the literatures are reviewed.

Microscopic endometrial perivascular epithelioid cell nodules: a case report with the earliest presentation of a uterine perivascular epithelioid cell tumor

Abstract

Perivascular epithelioid cell (PEC) tumors (PEComas) are a family of related mesenchymal tumors composed of PECs which co-express melanocytic and smooth muscle markers. Although their distinctive histologic, immunohistochemical, ultrastructural, and genetic features have been clearly demonstrated, their histogenesis and normal counterpart remain largely unknown. Precursor lesions of PEComas have rarely been reported. We herein describe a tuberous sclerosis patient with microscopic PEC nodules in the endometrium of adenomyosis, pelvic endometriosis, an ovarian endometriotic cyst, and the endometrium of the uterine cavity. The nodules showed a mixture of spindle-shaped and epithelioid cells concentrically arranged around small arteries. The cells exhibited uniform nuclei, light eosinophilic cytoplasm, and immunoreactivity with HMB-45 and CD10. Some nodules revealed continuity with a PEComa in the myometrium. These findings support microscopic endometrial PEC nodules possibly being precursor lesions of uterine PEComas. The wide distribution of the nodules in the pelvis may be related to the multicentricity of PEComas in tuberous sclerosis patients. Owing to the immunoreactivity with CD10, microscopic endometrial PEC nodules may be misinterpreted as endothelial stromal cells unless melanocytic markers are stained. To the best of our knowledge, this is a case with the earliest manifestation of PEC lesions occurring in the endometrium.

Virtual Slides

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"Malignant" perivascular epithelioid cell neoplasm: risk stratification and treatment strategies

Purpose. Perivascular epithelioid cell tumors (PEComas) are a rare collection of tumors characterized by a myomelanocytic phenotype, and PEComas occurring in “nonclassic” anatomic distributions are known as perivascular epithelioid cell tumor not otherwise specified (PEComa-NOS). This review aims to compile and analyze cases of PEComa-NOS in an effort to better define their natural history. Design. We evaluated all 234 cases of PEComa-NOS reported in the English literature, extracting information regarding diagnostic features, treatment approaches, and outcomes. Multivariate analysis of a number of variables evaluable on pathologic review was performed to refine preexisting risk stratification criteria. Outcomes for patients receiving nonsurgical treatment are also reported. Results. Primary tumor size ≥5 cm (P = 0.02) and a high (1/50 HPF) mitotic rate (P < 0.0001) were the only factors significantly associated with recurrence following surgical resection. Cytotoxic chemotherapy and radiation therapy have shown little benefit in treating PEComa-NOS; mTOR inhibition is emerging as a treatment option. Conclusion. Progress has been made in understanding the natural history and molecular biology of PEComa-NOS. This review further clarifies risk of recurrence in this disease, allowing clinicians to better risk stratify patients. Further work should focus on applying this knowledge to making treatment decisions for patients with this disease.

Multifocal PEComa (PEComatosis) of the female genital tract and pelvis: a case report and review of the literature

Perivascular epithelioid cells (PECs) are constantly present in a group of tumors called PEComas, including angiomyolipoma (AML), clear-cell "sugar" tumor (CCST) of the lung and extrapulmonary sites, lymphangioleiomyomatosis, clear-cell myomelanocytic tumor of the falciform ligament/ligamentum teres and rare clear-cell tumors of other anatomic sites. PECs have distinctive morphologic, immunohistochemical, ultrastructural and genetic characteristics, including an epithelioid appearance with a clear to granular cytoplasm, a round to oval, centrally located nucleus, and an inconspicuous nucleolus. PECs also express melanocytic and myogenic markers like HMB45 and smooth muscle actin. PEComa is rare in human, and multifocal PEComas (PEComatosis) is extremely rare. Up to now there have been only less than 5 cases described in the literature. Here we report a 46-year old Chinese woman who had PEComatosis arising from the genital tract and pelvis. To our knowledge, this is the first case of PEComatosis ever reported in China.

Perivascular epithelioid cell tumors (PEComas) of the head and neck: report of three cases and review of the literature

PEComas are a family of neoplastic lesions that share overlapping morphology, immunohistochemistry, and ultrastructure that include angiomyolipoma, lymphangioleiomyomatosis, clear cell "sugar" tumor of the lung as well as similar tumors occurring in a variety of visceral, cutaneous and soft tissue sites throughout the body. The defining histopathological features are epithelioid cells with a perivascular distribution containing clear to pale eosinophilic granular cytoplasm and a round-to-oval centrally located nucleus with an inconspicuous nucleolus. Immunohistochemically, coexpression of melanocytic (HMB-45 and/or Melan-A) and myoid markers are characteristic. In the present study, we describe three PEComas occurring in the head and neck (nasal cavity and larynx) and discuss the behavior of these distinctive tumors and review the literature of head and neck PEComas. The importance of recognizing this entity will ensure its consideration in the differential diagnosis of tumors of the head and neck with a similar morphology. The histogenesis of PEComas still remains elusive and additional cases with a prolonged follow up remain important to accurately determine the behavior of these distinctive tumors. Complete surgical excision still remains the treatment of choice for histologically benign PEComas.

Heterologous and rare homologous sarcomas of the uterine corpus: a clinicopathologic review

Pure sarcomas of the uterine corpus are uncommon, constituting less than 3% of all malignancies at this site, and most of them are leiomyosarcomas and endometrial stromal sarcomas. Rare histotypes of homologous sarcomas and heterologous sarcomas are occasionally encountered, and the absence of significant accumulated experience with these histotypes at this location may potentially raise diagnostic and patient management difficulties. In this article, the clinicopathologic attributes of all earlier reported sarcomas of the uterine corpus other than leiomyosarcomas and endometrial stromal sarcomas are summarized. Included are embryonal rhabdomyosarcoma, pleomorphic rhabdomyosarcoma, angiosarcoma, alveolar soft part sarcoma, malignant perivascular epithelioid cell tumors (PEComas), osteosarcoma, chondrosarcoma, liposarcomatous tumors, malignant extrarenal rhabdoid tumors, Ewing sarcoma/primitive neuroectodermal tumor, and other rare histotypes. Embryonal rhabdomyosarcoma (20%), Ewing sarcoma/primitive neuroectodermal tumor (17%), angiosarcoma (14%), and pleomorphic rhabdomyosarcoma (13%) appeared to be more common than the others, although there was no single overwhelmingly prevalent histotype in the group. A subset, including embryonal rhabdomyosarcoma, alveolar soft part sarcoma, and PEComas, peak in the premenopausal years, but most of the others were observed in postmenopausal women. Favorable outcomes have been reported for the patients diagnosed with alveolar soft part sarcoma, and the prognosis for their counterparts with PEComa remains a matter of debate. Multimodal therapeutic approaches to contemporary patients with embryonal rhabdomyosarcomas have resulted in significantly improved outcomes. Unfortunately, most of the other sarcomas have been associated with rapid tumor progression and unfavorable patient outcomes. The differential diagnosis for these sarcomas is often extensive and varies by histotype, but their accurate diagnosis fundamentally requires the careful exclusion of biphasic malignancies.

Clinicopathologic features of 2 new cases of uterine tumors resembling ovarian sex cord tumors

Uterine neoplasms showing an exclusive sex cord-like differentiation or focal low-grade sarcoma differentiation, designated as uterine tumors resembling ovarian sex cord tumors (UTROSCTs), are rare, with only 48 cases described earlier in international literature. Generally, this entity is characterized by benign behavior. In this study, we report the clinical and pathologic features of 2 peculiar new cases of UTROSCTs. In these examples, the pathologic diagnosis of UTROSCT was made incidentally after the clinical diagnosis of a leiomyoma and endometrial polyp. On examination of small biopsies, the diagnosis was facilitated by specific immunohistochemical analysis using markers for the sex cord component. In 1 of these cases, the patient, because of her young age and her desire to preserve her fertility, was only treated by minimally invasive hysteroscopic surgery. In the other case, the neoplasm seemed to be the consequence of tamoxifen treatment for breast carcinoma. After diagnosis, in this second case, the woman underwent hysterectomy that showed a residue of the tumor and cervical metastasis from the earlier breast carcinoma. The differential diagnosis of UTROSCT and the role of immunohistochemistry in confirming a diagnosis are discussed.

Perivascular epithelioid cell tumor of abdominal origin

Perivascular epithelioid tumor is not a common disease; therefore, large series are not available in the literature, and most are case reports. Histologic characteristics of these neoplasms are positivity to melanogenic (HMB-45) and muscle stains. All these neoplasms have the characteristic perivascular epithelioid cell or "PEC," but the term myomelanocyte tumor has been proposed because of the immunohistochemistry expression. Females are affected more commonly than males. The uterus seems to be one of the most common organs affected. Its clinical behavior is uncertain, and standard treatment has not been established as well as criteria for malignancy. We report 3 cases of abdominal PEComa, 1 of them with benign clinical outcome and 2 with an aggressive behavior.

PEComas: a review with emphasis on cutaneous lesions

The connection between angiomyolipoma (AML) of the kidney, clear cell sugar tumor (CCST) of the lung, and pulmonary lymphangioleiomyoma (LAM), was progressively discovered because of the histologic and immunophenotypic similarities between the three tumors and their frequent association with tuberous sclerosis complex (TSC). Morphologically, analogous lesions found in other locations are composed of the unifying cell, the perivascular epithelioid cell (PEC). PEC tumors (or PEComas), other than AML, CCST, and LAM, are not associated with TSC and typically occur in middle-aged adult females. These neoplasms are composed of nests and fascicles of clear to granular epithelioid and/or spindled cells with a consistent arrangement around blood vessels. Characteristically, the cells express both melanocytic (usually HMB45) and myogenic (typically actin) markers. Although the most common sites are the gastrointestinal and genitourinary tracts, approximately 23 cases, to date, of PEComas arising in the skin have been reported. Primary cutaneous PEComas also have a predilection for adult females and most often present as a painless mass on the extremities. In contrast to other sites, the myogenic marker most commonly expressed in PEComas of the skin is desmin. Most reported cutaneous PEComas follow a benign course, however, a malignant case has been reported. Surgical excision is currently the mainstay of treatment.

Perivascular epithelioid cell neoplasms: a systematic review of prognostic factors

Perivascular epithelioid cell tumors (PEComas) are rare, soft tissue tumors characterized by epithelioid cells with clear or eosinophilic cytoplasm and a perivascular disbursement. We compiled the treatment and follow-up results from an extensive collection of reported gynecologic PEComa cases and statistically analyzed their respective therapy modalities and corresponding patient outcomes. In the group of patients with PEComa who received surgical management alone, there was a tendency for them to exhibit a lower disease recurrence rate. Conversely, patients with PEComa who initially received surgery and chemotherapy or radiation therapy were associated with a higher disease recurrence rate (P =.024). Metastatic involvement was related to higher patient mortality rates (P =.0001), although this finding was unrelated to treatment type. Surgical management alone may suffice for nonaggressive lesions, but chemotherapy and radiotherapy appear necessary for patients who present with high-risk histologic condition or metastatic disease. Because PEComas exhibit varying biologic behavior and an ill-defined presentation, the treatment for these lesions necessitates further evaluation.

Perivascular epithelioid cell tumor

Perivascular epithelioid cell tumors are mesenchymal neoplasms defined by the presence of histologically and immunohistochemically distinctive perivascular epithelioid cells. The perivascular epithelioid cell has no known normal tissue counterpart and coexpresses myoid and melanocytic markers. This tumor family shows marked female predominance and includes angiomyolipoma, clear cell sugar tumor, lymphangioleiomyomatosis, and a group of rare, morphologically and immunophenotypically similar tumors arising at a variety of visceral and soft tissue sites. This latter subset has been collectively termed perivascular epithelioid cell tumors-not otherwise specified. They are usually composed of epithelioid, but occasionally spindled, cells with clear to granular eosinophilic cytoplasm and focal perivascular accentuation. The mainstay of treatment is wide excision. Although most cases are benign, a subset behaves in a malignant fashion. Since few malignant cases have been reported, firm criteria for malignancy have yet to be established. This review focuses on the perivascular epithelioid cell tumors-not otherwise specified subset.

Perivascular epithelioid cell tumor of the retroperitoneum in a young woman resulting in an abdominal chyloma

Perivascular epithelioid cell tumor (PEComa) is an extremely rare neoplasm which appears to have predominancy for young, frequently Asian, women. The neoplasm is composed chiefly of HMB-45-positive epithelioid cells with clear to granular cytoplasm and usually showing a perivascular distribution. These tumors have been reported in various organs under a variety of designations. Malignant PEComas exist but are very rare. The difficulty in determining optimal therapy, owing to the sparse literature available, led us to present this case. We report a retroperitoneal PEComa discovered during emergency surgery for abdominal pain in a 28-year-old Asian woman. The postoperative period was complicated by chylous ascites that was initially controlled by a wait-and-see policy with total parenteral nutrition. However, the chyle production gradually increased to more than 4 l per day. The development of a bacterial peritonitis resulted in cessation of production of abdominal fluid permitting normal nutrition without chylous leakage. Effective treatment for this rare complication of PEComa is not yet known; therefore, we have chosen to engage in long-term clinical follow-up.

Uterine perivascular epithelioid cell tumor coexisting with pulmonary lymphangioleiomyomatosis and renal angiomyolipoma: a case report

We present a case of uterine perivascular epithelioid cell tumor (PEComa) coexisting with both pulmonary lymphangioleiomyomatosis and renal angiomyolipoma. The patient was a 42-year-old woman, suffering from massive abnormal uterine bleeding, progressive dyspnea, and arterial hypertension. Her clinical history included diagnoses of bilateral renal angiomyolipoma and pulmonary lymphangioleiomyomatosis. The patient underwent a subtotal hysterectomy and the specimen contained a subserosal tumor with irregular outlines in addition to uterine leiomyomata. The uterine tumor was histologically composed of solid sheets and tonguelike infiltration and lymphangioleiomyomalike structures within the myometrium, formed by epithelioid cells with ovoid to round nuclei and clear to light eosinophilic cytoplasms. The tumor did not display any morphologic sign of malignancy. The tumor cells showed expression of HMB-45 and smooth muscle markers. Ultrastructural analysis revealed abundant cytoplasmic microfilaments and rare small cytoplasmic bodies with a gridlike lining. We conclude that identification of lymphangioleiomyomalike growth pattern may aid in the differential diagnosis of uterine PEComa and suggest using both PEComa and smooth muscle tumor terminology.

Perivascular epithelioid cell tumor of the rib

We present a rare case of perivascular epithelioid cell tumor (PEComa) in the right 6th rib of a 28-year-old man. A plain computed tomography scan showed a round osteolytic lesion in the right 6th rib. The resected tissue contained a globular-shaped, soft tumor. Histologically, the tumor was rich in vasculature and exclusively composed of perivascular epithelioid cells with clear cytoplasm. Immunohistochemically, the tumor expressed diffusely a melanocyte marker, human melanoma black-45, and focally a myogenic marker, alpha-smooth muscle actin, but not an epithelial marker, AE1/AE3. Fontana-Masson-positive melanin pigments were present and c-kit receptor tyrosine kinase (CD117), involved in the development of melanocytes but not myogenic cells, was expressed in tumor cells. These findings indicate that the tumor is PEComa with some differentiation into melanocytes. Notably, owing to the unique location of the occurrence, the tumor occupied bone marrow tissues of the rib, resulting that the tumor has the potential for hematogenous metastasis. In spite of the lack of cells with severe atypia, necrosis, and numerous mitoses, tumor cells invaded into surrounding tissues and overexpressed cyclin D1. To the best of our knowledge, this is the first case report of PEComa arising from the rib with the signs of malignant potential.

Multifocal PEComa (PEComatosis) of the Female Genital Tract Associated With Endometriosis, Diffuse Adenomyosis, and Endometrial Atypical Hyperplasia

The authors describe a case of multifocal perivascular epithelioid cell tumor (PEComa) arising in the pelvis of a 39-year-old woman affected by tuberous sclerosis. The tumor presented in the form of multiple fascicular, focally cystic nodules involving the uterine corpus, both ovaries, and the omentum. Microscopically, the nodules were composed of foci of adenomyosis and endometriosis (with focal atypical complex hyperplasia) associated with a stromal spindle cell population immunoreactive for HMB-45, smooth muscle actin, and estrogen and progesterone receptors. We interpret these foci as the result of a widespread proliferation of perivascular epithelioid cells (PEC). Because of the diffuse quality of the process, the designation of PEComatosis seems warranted.

Uterine PEComa: appraisal of a controversial and increasingly reported mesenchymal neoplasm

In recent years, a group of tumors that have been designated "perivascular epithelioid cell tumors" (PEComa) have been reported with increasing frequency from a wide variety of anatomic locations. The uterus and retroperitoneum appear to be the most frequent sites of origin for these lesions. PEComas belong to an identically named family of tumors comprised of conventional angiomyolipomas, clear cell sugar tumors, lymphangiomyomatosis and clear cell myomelanocytic tumor of the falciform ligament/ligament teres, and are also known as PEComa-NOS. This article is a primer for clinicians on the most salient clinicopathologic features of uterine PEComas, as most of the debate and discussion have taken place in the pathologic literature. The author appraises in detail the current state of knowledge on PEComas of the uterus based on a review of published data on the 44 previously reported cases, and comments on areas of controversy. The latter are centered predominantly on the significant morphologic and immunophenotypic overlap that exists between uterine PEComa and some smooth muscle tumors of the uterus. The clinicopathologic features of cases reported as epithelioid smooth muscle tumors and cases reported as uterine PEComas are compared and contrasted, and a practical approach to their reporting is proposed.

Perivascular epithelioid cell tumor (PEComa) of the uterus: an outcome-based clinicopathologic analysis of 41 reported cases

The uterus and retroperitoneum have emerged as the most frequently reported anatomic sites of origin of perivascular epithelioid cell tumors (PEComas), a poorly defined neoplasm that is characterized by varying amounts of spindle and epithelioid cells with clear to eosinophilic cytoplasm that display immunoreactivity for melanocytic markers, most frequently HMB-45. Published reports on 41 previously reported uterine PEComas are reviewed in this report. Of these 41 cases, 31 originating in the corpus and for which there was adequate follow-up information (or clinical malignancy) were categorized into 2 groups: (1) a malignant group that was comprised of cases associated with patient death of disease and/or clinical malignancy as evidenced by local and/or distant extension outside of the uterus (n=13, group 1) and (2) a "nonmalignant" group of cases in which neither of the above features were present (n=18, group 2). Groups 1 and 2 did not significantly differ regarding duration of follow-up (25 mo vs. 24.3 mo, respectively, P=0.9) or patient age (45.61 y vs. 43.46 y, respectively, P=0.7). Five of the group 1 patients experienced distant (extra-abdominal) metastases. The group 1 tumors were significantly larger than the group 2 tumors (averages 9.6 cm vs. 4.67 cm respectively, P=0.04); however, there were no size thresholds that, in of themselves, reliably classified 75% or more of the cases in both groups. Coagulative necrosis was highly associated with group 1, being present in 82% of cases as compared with only 11.8% of group 2 cases (P=0.0002). Eighty-eight percent of the group 2 cases had a mitotic rate of <or=1/10 high power fields (HPF) as compared with 40% of group 1 cases (P=0.01). However, the absence of mitotic activity did not rule out malignancy, as 2 of the group 1 cases lacked mitotic activity and displayed metastases. Twenty-five percent, 49%, 56%, 73%, and 100% of tested cases displayed immunoreactivity for CD10, desmin, vimentin, smooth muscle actin, and caldesmon, respectively. PEComas are tumors of uncertain histogenesis and malignant potential that seem to display some morphologic and immunophenotypic overlap with smooth muscle neoplasia. A mitotic count of >1/10 HPF and/or coagulative necrosis are features that, if present, raise the definite potential for aggressive behavior.

PEComas: the past, the present and the future

The perivascular epithelioid cell (PEC) is a cell type constantly present in a group of tumors called PEComas. PEC expresses myogenic and melanocytic markers, such as HMB45 and actin. Recently, recurrent chromosomal alterations have been demonstrated in PEC. At present, PEComa is a widely accepted entity. In the past 10 years, the use of this term has allowed to report and describe numerous cases permitting to start highlighting the biology of this group of lesions. PEComas are related to the genetic alterations of tuberous sclerosis complex (TSC), an autosomal dominant genetic disease due to losses of TSC1 (9q34) or TSC2 (16p13.3) genes which seem to have a role in the regulation of the Rheb/mTOR/p70S6K pathway. There are some open questions about PEComas regarding its histogenesis, the definition of epithelioid angiomyolipoma and the identification of the histological criteria of malignancy. An innovative therapeutic trial using rapamycin is under way for tumors occurring in TSC such as renal angiomyolipoma and lymphangioleiomyomatosis. Its success could provide the rationale for the use of the same drug in other lesions composed of PECs, especially in the malignant ones.