Perivascular epithelioid cell neoplasms of soft tissue and gynecologic origin: a clinicopathologic study of 26 cases and review of the literature

Primary perivascular epithelioid cell tumour (PEComa) of the prostate

Perivascular epithelioid cell tumours (PEComas) are a family of rare mesenchymal tumours arising in various anatomic locations. PEComas are defined by the presence of perivascular epithelioid cells that coexpress muscle and melanotic markers, especially HMB-45. They have unpredictable biological behaviour and are mostly benign, but some tumours can become unresectable or metastatic. Surgical resection, when possible, is the best treatment option. Radiation therapy, cytotoxic chemotherapy or immunotherapy have been reported as treatment options, either alone or in combination therapy. Prostatic PEComa is extremely rare, with only 1 malignant case reported. We report the first case of prostatic PEComa, which was benign and treated with transurethral resection.

Malignant mesenteric perivascular epithelioid cell neoplasm presenting as an intra-abdominal fistula in a 49-year-old female

Perivascular epithelioid cell tumors are rare mesenchymal tumors arising from histologically and immunohistochemically distinctive perivascular epithelioid cells that express both myogenic and melanocytic markers. These tumors are known to arise from different organs in the body and usually have an unpredictable clinical course. We report a case of a 49-year-old female who presented with diffuse abdominal pain, fever, chills, and nonbilious vomiting for a day. Work-up revealed a mesenteric mass measuring 13.5 × 7.7 × 9.5 cm, arising in the mesentery of the hepatic flexure, with adjacent gas suggestive of fistularization into the right colon. An exploratory laparotomy with resection of the mesenteric mass was performed, and the initial histopathology results were compatible with either an adenocarcinoma or a sarcoma; however, because of poor differentiation it was difficult to make a definitive diagnosis. However, final histopathology results revealed a malignant perivascular epithelioid cell tumor (with reservation that a S100 negative metastatic melanoma must be excluded clinically). Following surgery the patient was started on everolimus, an m-TOR inhibitor, and has shown good response to this medication.

Metastatic perivascular epithelioid cell tumor responding to mammalian target of rapamycin inhibition

Perivascular epithelioid cell tumors (PEComa) are a family of rare mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. Female genital tract and retroperitoneum are common sites of origin of PEComa-not otherwise specified. Diagnosis depends upon characteristic morphology and immunohistochemistry findings. Prognosis of unresectable or metastatic disease is poor. Responses to mammalian target of rapamycin (mTOR) inhibition are encouraging but mostly short-lived. We report a case of metastatic PEComa who responded to mTOR inhibition, albeit for a short duration. We also review the existing literature on mTOR inhibitors in PEComa.

Uterine smooth muscle tumors with features suggesting fumarate hydratase aberration: detailed morphologic analysis and correlation with S-(2-succino)-cysteine immunohistochemistry

Rare, sporadic uterine leiomyomas arise in the setting of severe metabolic aberration due to a somatic fumarate hydratase mutation. Germline mutations account for the hereditary leiomyomatosis and renal cell carcinoma syndrome, which predisposes for cutaneous and uterine leiomyomas and aggressive renal cell carcinomas. Altered fumarate hydratase leads to fumarate accumulation in affected cells with formation of S-(2-succino)-cysteine, which can be detected with the polyclonal antibody. High levels of these modified cysteine residues are found characteristically in fumarate hydratase-deficient cells but not in normal tissues or tumors unassociated with hereditary leiomyomatosis and renal cell carcinoma syndrome. We hypothesized that S-(2-succino)-cysteine-positive leiomyomas, indicating fumarate hydratase aberration, have morphologic features that differ from those without S-(2-succino)-cysteine positivity. Hematoxylin and eosin-stained slides of uterine smooth-muscle tumors were prospectively analyzed for features suggesting hereditary leiomyomatosis and renal cell carcinoma syndrome, such as prominent eosinophilic macronucleoli with perinucleolar halos, yielding nine cases. Germline genetic testing for fumarate hydratase mutations was performed in three cases. A detailed morphological analysis was undertaken, and S-(2-succino)-cysteine immunohistochemical analysis was performed with controls from a tissue microarray (leiomyomas (19), leiomyosarcomas (29), and endometrial stromal tumors (15)). Of the nine study cases, four had multiple uterine smooth muscle tumors. All cases had increased cellularity, staghorn vasculature, and fibrillary cytoplasm with pink globules. All cases had inclusion-like nucleoli with perinuclear halos (7 diffuse, 1 focal). All showed diffuse granular cytoplasmic labeling with the S-(2-succino)-cysteine antibody. Two of three tested patients had germline fumarate hydratase mutations. Only one leiomyoma from the tissue microarray controls was immunohistochemically positive, and it showed features similar to other immunohistochemically positive cases. Smooth-muscle tumors with fumarate hydratase aberration demonstrate morphological reproducibility across cases and S-(2-succino)-cysteine immuno-positivity. Although the features described are not specific for the germline fumarate hydratase mutation or the hereditary leiomyomatosis and renal cell carcinoma syndrome, their presence should suggest fumarate hydratase aberration. Identifying these cases is an important step in the diagnostic workup of patients with possible hereditary leiomyomatosis and renal cell carcinoma.

Extrapulmonary lymphangioleiomyoma: clinicopathological analysis of 4 cases

BACKGROUND

Lymphangioleiomyomatosis (LAM) is a slowly progressive neoplastic disease that predominantly affects females. Usually, LAM affects the lung; it can also affect extrapulmonary sites, such as the mediastinum, the retroperitoneum, or the lymph nodes, although these locations are rare. A localized form of LAM can manifest as extrapulmonary lesions; this form is referred to as extrapulmonary lymphangioleiomyoma (E-LAM). Due to the rare occurrence of E-LAM and its variable, atypical location, E-LAM is often difficult to diagnose. Herein, we report the clinicopathological information from four E-LAM cases, and also review previous articles investigating this disease.

METHODS

Four patients with E-LAM were identified at the Samsung Medical Center (Seoul, Korea) from 1995 to 2012. All E-LAM lesions underwent surgical excision.

RESULTS

All patients were females within the age range of 43 to 47 years. Two patients had para-aortic retroperitoneal masses, while the other two patients had pelvic lesions; two out of the four patients also had accompanying pulmonary LAM. In addition, no patient displayed any evidence of tuberous sclerosis. Histologically, two patients exhibited nuclear atypism with cytologic degeneration.

CONCLUSIONS

E-LAM should be considered in the differential diagnosis of patients presenting with pelvic or para-aortic masses. We also conclude that further clinical and pathological evaluation is needed in patients with E-LAM and nuclear atypism.

Bone metastases from bladder perivascular epithelioid cell tumor - an unusual localization of a rare tumor: a case report

Introduction

Perivascular epithelioid cell tumors are mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epithelioid cells. This type of tumor is rare but bladder localization is even rarer.

Case presentation

A case of bone metastatic bladder perivascular epithelioid cell tumor in a 65-year-old Caucasian man treated with surgery and chemotherapy is described and compared with other reports in the literature.

Conclusions

The rarity of perivascular epithelioid cell tumors hinders the development of a standard therapeutic approach, and thus requires case report descriptions. There is a need for cooperative studies to enlarge the case series and establish the best treatment strategy for this rare disease.

Hormonal manipulation with letrozole in the treatment of metastatic malignant pecoma

Perivascular epithelioid cell tumours (pecomas) are rare mesenchymal tumours. Some have a benign course; others metastasize. Treatment of malignant pecomas is challenging, and little is known about treatment for patients with metastatic disease. Here, we report a case of metastatic malignant pecoma with estrogen and progesterone receptor expression that showed a favourable and sustained response to letrozole.

Hepatic PEComa: a potential pitfall in the evaluation of hepatic neoplasms

Perivascular epithelioid cell tumour (PEComa) of the liver is very uncommon and may be overlooked in the clinical and histological differential diagnosis of a liver tumour. We report the case of an incidentally discovered liver mass suspicious for hepatocellular carcinoma, which on biopsy was suggestive of a pseudocyst but after resection was found to be hepatic PEComa with some of the usual characteristics of this neoplasm as well as several less familiar features. We have also reviewed cases of hepatic PEComa from the literature in order to provide insight into recognising possible PEComa preoperatively and assessing its risk of malignancy after diagnosis.

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.

Use of immunohistochemistry in the diagnosis of miscellaneous and metastatic tumors of the uterine corpus and cervix

Uncommon tumors in the uterus present diagnostic challenges. In some cases, the tumor subtype is usually seen outside the gynecologic tract and the possibility of a uterine primary is not considered. In other cases, histologic overlap with more common uterine tumors leads to potential misdiagnosis. Finally, metastatic carcinoma may involve the uterus and cervix. Rarely, symptoms related to the uterine metastasis may precede diagnosis of an extrauterine primary. Without the proper clinical context, the possibility of a missed diagnosis is increased. One must first be aware of these possibilities, but immunoperoxidase studies are often necessary to confirm the diagnosis. In this review, unusual and metastatic tumors involving the uterine corpus and cervix and immunoperoxidase studies used to diagnosis such tumors are discussed.

Frequent expression of KIT in endometrial stromal sarcoma with YWHAE genetic rearrangement

Endometrial stromal sarcomas with the YWHAE-NUTM2A/B genetic fusion characteristically contain high-grade round to epithelioid cell component that is strongly and diffusely cyclin D1-positive and it may or may not show an associated low-grade fibroblastic/myxoid cell component. They are clinically more aggressive than endometrial stromal sarcomas with the JAZF1-SUZ12 genetic fusion and frequently demonstrate extrauterine extension at initial clinical presentation. In this setting, the tumor may be misdiagnosed as gastrointestinal stromal tumor. This study examines the expression of KIT and ANO1 in 14 YWHAE-NUTM2A/B tumors by immunohistochemistry. Staining localization was determined as membranous and/or cytoplasmic, and the staining intensity was assessed (negative, weak, moderate and strong). Of the 14 tumors, 6 contained only a high-grade round cell component, 2 only a low-grade fibroblastic component and 6 had both components in the slides evaluated. The high-grade round cell component displayed moderate to strong membranous/cytoplasmic KIT staining in all tumors (12 of 12). The low-grade fibroblastic cell component showed only weak cytoplasmic KIT staining in 3 of 8 tumors. In contrast, ANO1 was negative in all 14 neoplasms, irrespective of the component evaluated. Sanger sequencing analysis (exons 9, 11, 13 and 17) and Ampliseq Cancer Panel mutation screen (Ion Torrent) demonstrated no KIT mutations in three KIT-positive YWHAE-NUTM2A/B tumors. This study shows that the high-grade round cell component of YWHAE-NUTM2A/B endometrial stromal sarcoma consistently expresses KIT but lacks KIT hotspot mutations. KIT expression may represent a potential diagnostic pitfall in the evaluation of YWHAE-NUTM2A/B endometrial stromal sarcoma presenting with pelvic/abdominal mass, particularly in situations where its uterine origin is not definitive, and thus a panel of antibodies that includes ANO1 and cyclin D1 is necessary.

Imaging features of primary and metastatic malignant perivascular epithelioid cell tumors

OBJECTIVE

The objective of our study was to describe the imaging features of primary and metastatic malignant perivascular epithelioid cell tumors (PEComas).

MATERIALS AND METHODS

In this retrospective study, 36 patients (26 women, 10 men; mean age, 53.1 years; age range, 35-77 years) with a histopathologically confirmed diagnosis of malignant PEComa who were seen at our institute between January 2007 and December 2012 were included. Pretreatment imaging of the primary tumor in 17 patients (CT, n = 13; MRI, n = 9; ultrasound, n = 5) and follow-up imaging in all 36 patients (CT, n = 36; MRI, n = 7) were reviewed by three radiologists in consensus.

RESULTS

The most common site of presentation of malignant PEComas was the retroperitoneum (38.9%) followed by the female genital tract (27.8%). Kidneys (8/36) and uterus (8/36) were the organs most frequently involved. The mean largest dimension was 11.01 cm (range, 4.5-25 cm). Primary tumors were well-circumscribed masses (16/17), were heteroechoic on ultrasound (5/5), were hypodense (2/6) to isodense (4/6) enhanced significantly (11/12) and compared with the paraspinal muscles on CT, were hypointense to isointense compared with skeletal muscle on T1-weighted imaging (8/9), were heterogeneously hyperintense compared with skeletal muscle on T2-weighted imaging (9/9), and showed significant post-gadolinium enhancement (7/7) on MRI. Of the 17 primary tumors, necrosis was seen in seven tumors, hemorrhage in three tumors, and calcification in three tumors. Twenty-six of 36 (72%) patients developed metastases, most commonly to the lung (21.6%), liver (17.6%), and peritoneum (10.8%).

CONCLUSION

Malignant PEComas in our study were large tumors that most often arise in the kidneys and uterus and metastasize to lungs, liver, or peritoneum. In our experience malignant PEComas should be considered in the differential diagnosis of large well-circumscribed renal and uterine tumors.

Diagnostic use of immunohistochemistry in uterine mesenchymal tumors

Immunohistochemistry may be helpful in the diagnosis of mesenchymal uterine tumors. This article reviews the immunoreactions used most frequently in the diagnosis of uterine smooth muscle tumors, endometrial stromal tumors, undifferentiated endometrial sarcomas, UTROSCTs, PEComas, adenomyomas, adenosarcomas and carcinosarcomas.

Perivascular epithelioid cell tumor located retroperitoneally with pulmonary lymphangioleiomyomatosis: report of a case

Perivascular epithelioid cell neoplasms, also known as "PEComas", are unusual mesenchymal tumors, exhibiting perivascular epithelioid cell differentiation and characterized by a mixed myogenic and melanocytic phenotype. "PEComas not otherwise specified" (PEComas-NOS) are especially rare; consequently, there are no published large series, but only case reports. These tumors are rarely located retroperitoneally, with only about 15 such cases reported. We report a case of pulmonary diffuse lymphangioleiomyomatosis with large retroperitoneal PEComa-NOS in a 66-year-old woman. Treatment consisted only of tumor resection, without additional adjuvant therapy. We emphasize the importance of correct immunohistochemistry diagnosis, initiation of recommended treatment, and surveillance of this unique family of tumors.

Neoadjuvant sirolimus for a large hepatic perivascular epithelioid cell tumor (PEComa)

Perivascular epithelioid cell tumors (PEComas) are rare soft-tissue tumors with an extremely heterogeneous clinical behavior. They may arise in different organs and may behave indolently or sometimes metastasize with different grades of biological aggressiveness. We report the case of a young woman with a primary inoperable PEComa of the liver with malignant histological features. Since the mTOR pathway is often altered in PEComas and responses have been reported with mTOR-inhibitors such as sirolimus or temsirolimus, we decided to start a neoadjuvant treatment with sirolimus. The patient tolerated the treatment fairly well and after 8 months a favorable tumor shrinkage was obtained. The patient then stopped sirolimus and 2 weeks later underwent partial liver resection, with complete clinical recovery and normal liver function. The histological report confirmed a malignant PEComa with vascular invasion and negative margins. Then 6 additional months of post-operative sirolimus treatment were administered, followed by regular radiological follow-up. For patients with a large and histologically aggressive PEComa, we think that neoadjuvant treatment with mTOR-inhibitor sirolimus may be considered to facilitate surgery and allow early control of a potentially metastatic disease. For selected high-risk patients, the option of adjuvant treatment may be discussed.

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.

Value of melanocytic-associated immunohistochemical markers in the diagnosis of malignant melanoma: a review and update

Since the identification of S100 protein as an immunohistochemical marker that could be useful in the diagnosis of melanoma in the early 1980s, a large number of other melanocytic-associated markers that could potentially be used to assist in the differential diagnosis of these tumors have also been investigated. A great variation exists, however, among these markers, not only in their expression in some subtypes of melanoma, particularly desmoplastic melanoma, but also in their specificity because some of them can also be expressed in nonmelanocytic neoplasms, including various types of soft tissue tumors and carcinomas. This article reviews the information that is currently available on the practical value of some of the markers that have more often been recommended for assisting in the diagnosis of melanomas, including those that have only recently become available.

PEComa of soft tissues can mimic lymph node relapse in patients with history of testicular seminoma

Perivascular Epithelioid Cell tumour (PEComa) is rare. We describe a 39-year-old man who underwent a left radical orchidectomy and adjuvant radiation therapy for a stage IA classical testicular seminoma. He was diagnosed with a mass lateral to the right common iliac artery that was considered suspicious for late lymph node relapse after 3 years of follow-up. Due to the unusual location of the mass and the equivocal findings of percutaneous biopsy, a laparoscopic pelvic lymphadenectomy was performed. Final pathology revealed PEComa of soft tissue. The patient is disease-free after 38 months of follow-up without adjuvant treatment. The presence of rare soft-tissue neoplasm should be considered in differential diagnosis of retroperitoneal masses during follow-up of germ cell tumours. Suspicious isolated recurrences of these neoplasms in unusual locations can require surgical excision to confirm diagnosis and avoid inappropriate treatment.

Fertility sparing treatment of a malignant uterine perivascular epithelioid cell tumor: A case report

•Perivascular epithelioid cell tumors (PEComas) are a family of rare, poorly defined mesenchymal tumors of uncertain malignant potential.•Treatment for PEComas has most commonly involved excisional biopsy or surgical resection.•The use of mTOR inhibitors may provide the best medical treatment as well as a fertility-sparing treatment option.

PEComa of the nasal cavity with worrisome histologic features and benign behavior: a case report

OBJECTIVES

PEComas (perivascular epithelioid cell tumors) are a family of neoplastic lesions that share overlapping ultrastructure and morphological and immunohistochemical appearance and include angiomyolipoma, lymphangioleiomyomatosis, and clear cell "sugar" tumor of the lung, as well as similar tumors that occur in a variety of visceral, cutaneous, and soft tissue sites throughout the body.

METHODS

A 40-year-old woman came to medical attention because of epistaxis and because of unilateral nasal obstruction of 3 months' duration. Endoscopic examination revealed a well-demarcated exophytic lesion attached to the anterior portion of the middle turbinate.

RESULTS

The lesion was superficially located, and therefore amenable to complete surgical excision. Seven years after surgery, the patient is alive and well, without evidence of local recurrence or metastastic disease. Based on morphological and immunohistochemical appearance, a diagnosis of PEComa with worrisome histologic features was rendered.

CONCLUSIONS

In the present study, we describe a PEComa that occurred in the nasal cavity and discuss the behavior of this entity. The importance of recognizing this disease will ensure its consideration in the differential diagnosis of tumors of the head that have similar morphological features. The histogenesis of PEComa still remains elusive, and collection of additional cases with a prolonged follow-up will be important in accurately determining the behavior of these distinctive tumors.

Perivascular epithelioid cell tumor of the rectum: report of a case and review of the literature

We report a case of perivascular epithelioid cell tumor arising in the rectum of a 55-year-old woman. The tumor was treated by transanal endoscopic microsurgery. After 1 year follow-up, the patient is alive with no radiologic or endoscopic evidence of recurrence. Perivascular epithelioid cell tumor is a rare mesenchymal tumor characterized by co-expression of melanocytic and smooth muscle markers. This rare tumor can arise in various organs, including the falciform ligament, uterus, uterine cervix, liver, kidney, lung, breast, cardiac septum, pancreas, prostate, thigh, and gastrointestinal tract. Perivascular epithelioid cell tumor of the gastrointestinal tract is very rare, with only 23 previously reported cases. We review the literature on perivascular epithelioid cell tumors arising in the gastrointestinal tract.

Perivascular epitheloid cell tumor (PEComa) mimicking retroperitoneal liposarcoma

PEComas are a collection of generally rare tumors, defined by the World Health Organization as ‘mesenchymal tumors composed of histologically and immunohistochemically distinctive perivascular epitheloid cells’. We describe the case of retroperitoneal PEComa with a liposarcoma-like appearance on cross-sectional imaging, but distinctive immunohistochemistry revealing the correct diagnosis.

Molecular cytogenetic analysis for TFE3 rearrangement in Xp11.2 renal cell carcinoma and alveolar soft part sarcoma: validation and clinical experience with 75 cases

Renal cell carcinoma with TFE3 rearrangement at Xp11.2 is a distinct subtype manifesting an indolent clinical course in children, with recent reports suggesting a more aggressive entity in adults. This subtype is morphologically heterogeneous and can be misclassified as clear cell or papillary renal cell carcinoma. TFE3 is also rearranged in alveolar soft part sarcoma. To aid in diagnosis, a break-apart strategy fluorescence in situ hybridization (FISH) probe set specific for TFE3 rearrangement and a reflex dual-color, single-fusion strategy probe set involving the most common TFE3 partner gene, ASPSCR1, were validated on formalin-fixed, paraffin-embedded tissues from nine alveolar soft part sarcoma, two suspected Xp11.2 renal cell carcinoma, and nine tumors in the differential diagnosis. The impact of tissue cut artifact was reduced through inclusion of a chromosome X centromere control probe. Analysis of the UOK-109 renal carcinoma cell line confirmed the break-apart TFE3 probe set can distinguish the subtle TFE3/NONO fusion-associated inversion of chromosome X. Subsequent extensive clinical experience was gained through analysis of 75 cases with an indication of Xp11.2 renal cell carcinoma (n=54), alveolar soft part sarcoma (n=13), perivascular epithelioid cell neoplasms (n=2), chordoma (n=1), or unspecified (n=5). We observed balanced and unbalanced chromosome X;17 translocations in both Xp11.2 renal cell carcinoma and alveolar soft part sarcoma, supporting a preference but not a necessity for the translocation to be balanced in the carcinoma and unbalanced in the sarcoma. We further demonstrate the unbalanced separation is atypical, with TFE3/ASPSCR1 fusion and loss of the derivative X chromosome but also an unanticipated normal X chromosome gain in both males and females. Other diverse sex chromosome copy number combinations were observed. Our TFE3 FISH assay is a useful adjunct to morphologic analysis of such challenging cases and will be applicable to assess the growing spectrum of TFE3-rearranged tumors.

Recently characterized soft tissue tumors that bring biologic insight

Previously unrecognized but clinicopathologically (and often molecularly) distinct types of soft tissue tumor continue to be characterized, allowing wider recognition, more consistent application of diagnostic criteria, more reliable prediction of tumor behavior and enhancement of existing classification schemes. Examples of such 'entities' that have become much better understood over the past decade or so include deep 'benign' fibrous histiocytoma, hemosiderotic fibrolipomatous tumor, PEComa, spindle cell liposarcoma, myoepithelial tumors of soft tissue and spindle cell/sclerosing rhabdomyosarcoma. These tumor types, as well as the insights which they have engendered, are briefly reviewed here.

PEComa: A Perivascular Epithelioid Cell Tumor in the Liver-A Case Report and Review of the Literature

Perivascular epithelioid cell tumors are soft tissue tumors that can occur in various locations in the body whose incidence is rising. Hepatic PEComas are quite rare and diagnosis involves positivity of Melan-A and HMB45 on immunohistochemistry. Usual treatment is surgery for benign tumors and chemotherapy including mTOR inhibitors for malignant tumors. Here we discuss the radiological and pathological diagnosis, evaluation, and management of a hepatic PEComa. We describe a 51-year-old patient who was diagnosed incidentally after unusual physical exam findings.

A huge malignant perivascular epithelioid cell tumor (PEComa) of the uterine cervix and vagina

Perivascular epithelioid cell tumors (PEComas) are a family of rare mesenchymal neoplasms, including angiomyolipoma, clear-cell "sugar" tumor of the lung and extrapulmonary sites, lymphangioleiomyomatosis, clear-cell myomelanocytic tumor of the falciform ligament/ligamentum teres, and clear-cell tumors at various other anatomic sites. These tumors are characterized by a proliferation of epithelioid cells with clear to eosinophilic cytoplasm, perivascular distribution, and coexpression of myogenic and melanocytic markers. PEComas show a female predominance, occur with some frequency in the gynecological tract, and have an unpredictable biological behavior. We report a case of a huge malignant PEComa arising from the uterine cervix and vagina. To the best of our knowledge, only 6 cases of PEComa in the cervix and 2 cases in the vagina have been reported in the literature.

Management of perivascular epithelioid cell tumor of the liver: A case report and review of the literature

Perivascular epithelioid cell tumor (PEComa) is a rare tumor that originates from mesenchymal tissues. Cases of PEComa in the liver are extremely rare. The present study aimed to analyze the clinical features of PEComa in the liver and discuss its management. Here we report a 25-year-old female with multiple lesions of low density with poorly defined borders in the liver, as shown by a computed tomography (CT) scan. A partial hepatectomy was proceeded and PEComa was diagnosed by immunohistochemistry. No evidence of recurrence was observed during the one year follow-up. A total of 20 patients with hepatic PEComa, including one case from the present study and 19 cases that were reported in literature between June 2001 and December 2012, were reviewed and analyzed. The mean patient age was 43.4 years (range, 25-67 years) and the cases consisted of 18 female and two male patients. The tumor size ranged between 2.0×1.6 and 15.0×12.0 cm. Of the 20 patients, nine were asymptomatic and 11 had mild to significant complaints. Immunohistochemistry plays a key role in the diagnosis of PEComa. All the cases in this study were strongly positive for human melanoma black-45. A surgical resection is the gold standard for curative intent. All the patients underwent a surgical resection and none were administered perioperative chemotherapy or radiotherapy. In total, 13 of the 14 patients with follow-up information survived during the 8-36-month follow-up period and one patient succumbed due to recurrence two years after the surgery.

Perivascular epithelioid cell tumor: the first malignant case report in the pancreas

Pancreatic perivascular epithelioid cell tumors (PEComas) are exceedingly rare neoplasms, <10 cases have been described; all were benign and occurring mostly in women. We report the first malignant pancreatic PEComa in a patient with BRCA2 mutation. A 51-year-old woman with a medical and familial history of breast adenocarcinoma, who was tested positive for BRCA2 mutation, presented with a recent history of jaundice. Imaging studies were consistent with endocrine or secondary tumor. Pathologic examination of fine needle aspiration biopsy and Whipple procedure revealed a 6-cm intrapancreatic PEComa, invading the duodenal wall with extensive necrosis and vascular invasion, leading to classify this PEComa into "malignant" category. The patient developed liver metastases 6 months after surgery. Although mostly benign, thorough sampling of the PEComa is mandatory, to rule out malignant behavior whatever the location of the tumor is.

Malignant renal angiomyolipoma with metastases in a child

The biological character of epithelioid angiomyolipoma (EAML) remains controversial and little is known about EAML in children. We present a case of a 7-year-old boy with abdominal distention, diagnosed as EAML. Under microscopy, epithelioid cells were observed, with eosinophilic or slightly eosinophilic cytoplasm and nuclear pleomorphism, thick-walled blood vessels, and some cells that were differentiated to smooth muscle cells or fat cells were easily observed. Immunochemical staining showed that Melan-A and HMB45 were positive. The tumor presented highly aggressive biobehavior. Furthermore, we reviewed and analyzed cases of diagnosed EAML in our hospital and those reported in the literature. Renal EAML (10/17) was most common, and the EAML of 3 of 17 patients metastasized to other organs.

Adenomyomatous Polyp of the Endometrium With Prominent Epithelioid Smooth Muscle Differentiation

A minor component of smooth muscle may be present in the stroma of benign endometrial polyps and 2 distinctive endometrial polypoid lesions, atypical polypoid adenomyoma and adenomyoma, are characterized by stroma with a predominant smooth muscle component. In this report, we describe 2 unusual endometrial polyps in 43- and 60-year-old women in which the stromal component was predominantly composed of smooth muscle with an epithelioid appearance, a phenomenon which, as far as we are aware, has not been previously reported.

Incidental perivascular epithelioid cell tumor in an inguinal hernia sac

Perivascular epithelioid tumors (PEComa) are uncommon mesenchymal neoplasms demonstrating positivity for muscular and melanocytic immuno-markers. Included in this category are angiomyolipoma, lymphangioleiomyomatosis, and clear cell sugar tumors. Lesions which do not fit into these categories are classified as "not otherwise specified". We present a case of an incidentally discovered PEComa within inguinal hernia sac contents in a 70-year-old woman. It consisted of spindled and epithelioid cells with bland oval nuclei, small nucleoli and clear to light eosinophilic cytoplasm. There was no atypia or mitoses. The lesion was strongly positive for HMB45 and smooth muscle actin. Pelvic soft tissue and peritoneal PEComas are rarely reported in literature and very little is known about their prognosis. We discuss the immunohistochemistry, differential diagnosis, and pathogenesis of PEComas.

Mesenchymal Tumors of the Gastrointestinal Tract Other than GIST

Mesenchymal tumors involve the gastrointestinal (GI) tract more frequently than other visceral organs. Many such tumors are small, and are benign and increasingly being detected incidentally during colonoscopic screening. Some tumors show distinctive features at this site, such as schwannoma and clear cell sarcoma-like tumor of the GI tract. Without knowledge of these features, recognition of these tumor types can be difficult. This reviews addresses recent developments and diagnostic features of mesenchymal tumors of the GI tract other than gastrointestinal stromal tumor (GIST).

Uncommon of the uncommon: malignant perivascular epithelioid cell tumor of the lung

A perivascular epithelioid cell (PEC) tumor is a rare mesenchymal tumor characterized by abundant cytoplasmic Periodic acid-Schiff positive glycogen (also called sugar tumor or clear cell tumor of the lung for this characteristic) and is mostly benign. We report a case of a 63-year-old man who presented with an enlarging mass on chest radiograph. After a thorough workup, diagnosis of malignant pulmonary PEC tumor with lung to lung metastases was established. Herein, the difficulties of diagnosis and management we confronted are described.

PEComa of the nose: report of a case with immunohistochemical and ultrustructural studies and a review of the literature

PEComas are a family of mesenchymal neoplasms that have in common the presence of a unique cell type, the perivascular epithelioid cell (PEC). PECs uniquely exhibit a distinct immunophenotype with expression of both melanocytic, particularly HMB-45, and myogenic markers. Nasal PEComas are exceedingly rare. To date, 14 cases have been described in the literature and with the exception of 6 cases, the rest consistently lack epithelioid cells and HMB-45 expression and are best classified as nasal hamartomas or angioleiomyomas with an adipocytic component. Nasal PEComas may closely resemble malignant melanomas since both entities share many morphologic, immunohistochemical, ultrastructural and clinical features. The distinction is of paramount importance as melanomas tend to display an aggressive behaviour with associated poor outcome. Herein, we report a case of nasal PEComa in a 19 year girl, focusing on the importance of light microscopic, immunohistochemical and ultrastructural features in accurately establishing the diagnosis.

Primary perivascular epithelioid cell tumour (PEComa) of the liver

We present a case of a 53-year-old woman with abdominal discomfort for 6 months. The liver was enlarged. Contrast CT scan of the abdomen revealed a 10 cm hypervascular tumour at the right lobe of the liver. Right hepatectomy with complete excision of the tumour was achieved. Histological and immunohistochemical findings were consistent with perivascular epithelioid cell tumour. She is regularly followed up with contrast CT assessment. There is no tumour recurrence 12 months after the operation.

Epithelioid angiomyolipoma of the liver: a clinicopathologic study of 5 cases

This study aimed to study the clinicopathologic characteristics of epithelioid angiomyolipoma, a variant of angiomyolipoma (AML) in the liver; and to discuss the diagnostic challenges. Five cases of primary liver epithelioid AML were retrieved from our archives from January 2003 to October 2012. The clinicopathologic features of each case were retrospectively reviewed. All 5 patients were female, with age ranging from 36 to 70 years (median, 41 years). The size of the tumor ranged from 1.2 to 25 cm. Histologically, the tumor comprised polygonal cells with granular eosinophilic cytoplasm and accompanied by immunohistochemical expression of HMB-45 ± Melan-A. Variations in growth pattern and cytology were observed. Estrogen receptor was negative in all 5 cases. None showed cytologic atypia, coagulative necrosis, increased mitotic count, or vascular invasion. Epithelioid AML is an uncommon primary liver tumor with a female predominance. The size of the tumor can be variable. This tumor might impose diagnostic difficulty both clinically and histologically. Immunohistochemical staining with melanocytic markers is a promising means to confirm the pathologic diagnosis. A careful assessment of aggressive histologic features is recommended to stratify the risk of aggressive behavior of this tumor.

Cutaneous PEComa does not harbour TFE3 gene fusions: immunohistochemical and molecular study of 17 cases

AIMS

The family of perivascular epithelioid cell tumours (PEComas) comprises a related group of mesenchymal tumours of uncertain origin that show both smooth muscle and melanocytic differentiation markers. TFE3 nuclear immunoreactivity may be viewed as a supporting marker, as it has been found in a subset of visceral PEComas. We immunohistochemically analysed 17 cases of primary cutaneous PEComas for TFE3, and five of them also for SOX-10, and also analysed them by FISH for TFE3 rearrangement.

METHODS AND RESULTS

PEComas presented as skin-coloured tumours, in 12 women and five men, with a median age of 49.5 years. Tumours showed either a mixed clear cell-epithelioid cell pattern or a monomorphous clear cell pattern. None of the primary cutaneous PEComas showed detectable TFE3 or SOX-10 positivity. FISH assay for TFE3 rearrangement yielded negative results in all of the tested tumours.

CONCLUSIONS

Cutaneous PEComas are mostly composed of clear cells, and, unlike a subset of visceral and deep-seated PEComas, cutaneous PEComas consistently lack TFE3 expression. Owing to the lack of SOX-10 expression, a neural crest origin could not be shown.

[A case of primary cutaneous PEComa]

BACKGROUND

PEComas (PEC: Perivascular epithelioid cell) are tumours expressing both melanocytic and myogenic markers. The clinical features are non-specific.

PATIENTS AND METHODS

A 55-year-old woman presented with a non-specific tumour on her right arm. Histological examination revealed an intradermal tumour composed of clear epithelial cells. The tumour was positive for HMB45 and protein S100, and was negative for Melan-A and actin. A diagnosis of PEComa was retained despite negative myogenic markers.

DISCUSSION

PEComas are neoplasms composed of nests and fascicles of clear to granular epithelioid cells that express both melanocytic markers (HMB45, Melan-A, NK1C3, tyrosinase) and myogenic markers (actin, caldesmin, desmin, calponin), whereas S100 protein and cytokeratins are usually absent. Included in this broad category are angiomyolipoma, clear-cell "sugar" tumours and lymphangioleiomyoma. Some deep PEComas may have a malignant course. Cutaneous primitive forms are exceptional and often benign. Histological differential diagnoses to consider are those of clear-cell tumours: paraganglioma-like dermal melanocytic tumour, melanoma, metastatic clear-cell renal carcinoma and epithelioid sarcoma. In our patient, a diagnosis of cutaneous primitive PEComa was retained despite the absence of myogenic markers and the positivity of the protein S100, based on the cytological and immunohistochemical features, which were not evocative of any other diagnosis.

CONCLUSION

Cutaneous PEComa are non-specific tumours. Histological analysis confirms the diagnosis and allows other more aggressive tumours to be ruled out.