Hepatic perivascular epithelioid cell tumors:The importance of preoperative diagnosis

Accurate preoperative diagnosis is highly important for the treatment of perivascular epithelioid cell tumors(PEComas)because PEComas are mainly benign tumors and may not require surgical intervention.By analyzing the causes,properties and clinical manifestations of PEComas,we summarize the challenges and solutions in the diagnosis of PEComas.

Epithelioid malignant peripheral nerve sheath tumor of the bladder and concomitant urothelial carcinoma: A case report

BACKGROUND Epithelioid malignant peripheral nerve sheath tumor(EMPNST)of the bladder is a rare entity with devastating features.These tumors are thought to originate from malignant transformation of pre-existing schwannomas of pelvic autonomic nerve plexuses,and unlike the conventional malignant peripheral nerve sheath tumor(MPNST),are not associated with neurofibromatosis.The tumor has dis-tinctive morphological,immunohistochemical and molecular features.Addi-tionally,it tends to be more aggressive and have a higher mortality.This is the first case that presents with a synchronous urothelial carcinoma of the bladder and the epithelioid variant of MPNST in the literature.It’s also the second re-ported case of EMPNST originating from the bladder wall.CASE SUMMARY In this case report,we present the detailed clinical course of a 71-year-old patient with EMPNST of the bladder alongside a literature review.CONCLUSION During the management of EMPNST cases,offering aggressive treatment moda-lities to the patient,such as radical cystectomy,is appropriate for the best chance to contain the disease,regardless of the tumor stage and the extent of local disease at initial diagnosis.

Clinical review and literature analysis of hepatic epithelioid angiomyolipoma in alcoholic cirrhosis: A case report

BACKGROUND Hepatic epithelioid angiomyolipoma(HEA)has a low incidence and both clinical manifestations and imaging lack specificity.Thus,it is easy to misdiagnose HEA as other tumors of the liver,especially in the presence of liver diseases such as hepatitis cirrhosis.This article reviewed the diagnosis and treatment of a patient with HEA and alcoholic cirrhosis,and analyzed the literature,in order to improve the understanding of this disease.CASE SUMMARY A 67-year-old male patient with a history of alcoholic cirrhosis was admitted due to the discovery of a space-occupying lesion in the liver.Based on the patient’s history,laboratory examinations,and imaging examinations,a malignant liver tumor was considered and laparoscopic partial hepatectomy was performed.Postoperative pathology showed HEA.During outpatient follow-up,the patient showed no sign of recurrence.CONCLUSION HEA is difficult to make a definite diagnosis before surgery.HEA has the poten-tial for malignant degeneration.If conditions permit,surgical treatment is recom-mended.

Uterine epithelioid trophoblastic tumor with the main manifestation of increased human chorionic gonadotropin:A case report

BACKGROUND Epithelioid trophoblastic tumor(ETT)is an extremely rare malignant gestational trophoblastic neoplasm commonly presenting with abnormal vaginal bleeding,abdominal pain,and increased human chorionic gonadotropin(hCG).This study reported a case of uterine ETT with the main manifestation being increased hCG.CASE SUMMARY A 39-year-old female was referred to the Ningbo Maternal and Child Hospital of China in December 2022,complaining of increased hCG levels for 1 month.Magnetic resonance imaging revealed gestational trophoblastic tumor,and hysteroscopic electrotomy and curettage of intrauterine hyperplasia were performed.The patient was diagnosed with uterine ETT through postoperative pathological examination and immunohistochemical results.Total laparoscopic hysterectomy and bilateral salpingectomy were performed,and hCG levels returned to normal.The patient was without recurrence during the postoperative 3-month follow-up.CONCLUSION This study reported a case of uterine ETT with the main manifestation being increased hCG,highlighting that ETT should be considered in the presence of abnormal hCG.A total laparoscopic hysterectomy is recommended.

Massive simultaneous hepatic and renal perivascular epithelioid cell tumor benefitted from surgery and everolimus treatment:A case report

BACKGROUND Perivascular epithelioid cell tumor(PEComa)is a rare mesenchymal neoplasm that predominantly affects the kidney and uterus.The occurrence of this tumor in the liver,particularly with simultaneous involvement of the liver and kidney,is exceedingly uncommon.Pathological diagnosis is the gold standard.PEComas usually show positive immunohistochemical staining for melanocytic(HMB-45,Melan-A)and myoid(SMA,muscle-specific actin)markers.CASE SUMMARY We presented a noteworthy case of malignant PEComa affecting both the liver and kidney in a 53-year-old man with tuberous sclerosis complex(TSC).FAT2 and TP73 mutations in the kidney were identified and positive expression of diagnostic markers including HMB-45,Melan A,and TFE3 were detected.In addition,we demonstrated that hepatic artery perfusion chemotherapy was ineffective for hepatic PEComa,while surgery remained the most effective approach.Everolimus showed an excellent efficacy in the postoperative treatment of the tumor.CONCLUSION Surgical treatment is preferred for malignant PEComa affecting liver and kidney,especially with TSC;everolimus is effective postoperatively.

Sclerosing epithelioid fibrosarcoma of the pancreas:A case report

BACKGROUND A sclerosing epithelioid fibrosarcoma(SEF)is a rare malignant fibroblastic soft tissue tumor that rarely occurs in intra-abdominal organs.A case of a SEF in the pancreatic head is reported herein,including its clinical manifestations,preoperative imaging features,gross specimen and pathological findings.CASE SUMMARY A 33-year-old male patient was admitted to Peking Union Medical College Hospital in December 2023 due to a one-year history of intermittent upper abdominal pain and the discovery of a pancreatic mass.The patient underwent an enhanced computed tomography scan of the abdomen,which revealed a welldefined,round mass with clear borders and calcifications in the pancreatic head.The mass exhibited progressive,uneven mild enhancement,measuring approximately 6.6 cm×6.3 cm.The patient underwent laparoscopic pylorus-preserving pancreaticoduodenectomy.Postoperative pathological examination revealed that the lesion was consistent with a SEF.At the 3-month postoperative follow-up,the patient did not report any short-term complications,and there were no signs of tumor recurrence.CONCLUSION SEFs are rare malignant fibrous soft tissue tumors.SEFs rarely develop in the pancreas,and its preoperative diagnosis depends on imaging findings,with confirmation depending on pathological examination and immunohistochemistry.Currently,only four cases of pancreatic SEF have been reported in studies written in English.This case is the first reported case of a pancreatic SEF by a clinical physician.

Primary hepatic epithelioid angiomyolipoma: A malignant potential tumor which should be recognized

AIM: To improve the clinical diagnosis and recognition of hepatic epithelioid angiomyolipoma(HEAML).METHODS: Four cases of primary HEAML were confirmed based on the pathology archive system in our hospital from January 2009 to November 2015. The general state, clinical symptoms, imaging manifestations, histological results and immunohistochemistry of these patients were retrospectively reviewed and analyzed. Studies of HEAML published in the last 15 years were collected from Pub Med and MEDLINE to summarize the clinical symptoms, imaging characteristics, pathological features and management of HEAML.RESULTS: Four cases of primary HEAML were retrieved from our archives. These included three female patients and one male patient, with a mean age of 41.8 ± 11.5 years(ranging from 31 to 56 years). The meantumor size was 7.3 ± 5.5 cm(ranging from 3.0 to 15 cm). In the contrast-enhanced imaging, the tumor was obviously enhanced in the arterial phase, but enhanced continuously or exhibited a slow-density masse during the venous and delayed phases. Histologically, the tumors mainly consisted of epithelioid cells that comprised approximately 95% of the total neoplastic mass. Although no metastases occurred in our patients, pathological studies revealed necrosis, mitotic figures and liver invasion in two patients, which indicates aggressive behavior. Immunohistochemical staining revealed that human melanoma black 45(HMB-45) and Melan-A were positive in 4 cases. We only identified 81 cases with primary HEAML, including our present patients, from 26 articles available from Pub Med and MEDLINE. The majority of the papers were published as case reports. Only 5(5/75, 6%) cases were associated with tuberous sclerosis complex(TSC). More than half(35/66) were discovered incidentally upon physical examination. Approximately 65%(22/34) of the patients were misdiagnosed with HCC or other tumors before surgery. Approximately 10%(8/81) of the patients with HEAML had recurrence or metastasis after surgery, which was a very high and alarming rate.CONCLUSION: HEAML is a very rare primary hepatic tumor that is often misdiagnosed before surgery. Patients should be followed closely after surgery because of its malignant potential.

Improving recognition of hepatic perivascular epithelioid cell tumor:Case report and literature review

A 58-year-old man presented with the chief complaint of abdominal bloating and was incidentally found to have a liver tumor.As diagnostic imaging studies could not rule out malignancy,the patient underwent partial resection of segment 3 of the liver.The lesion pathologically showed eosinophilic proliferation,in addition to immunohistochemical positivity for human melanoma black 45 and Melan-A,thereby leading to the diagnosis of a hepatic perivascular epithelioid cell tumor(PEComa).A PEComa arising from the liver is relatively rare.Moreover,the name ‘PEComa' has not yet been widely recognized,and the same disease entity has been called epithelioid angiomyolipoma(EAML),further diminishing the recognition of PEComa.In addition,PEComa imaging findings mimic those of malignant liver tumors,and clinically,this tumor tends to enlarge.Therefore,a PEComa is difficult to diagnose.We conducted a systematic review of PEComa and EAML cases and discuss the results,including findings useful for differentiating perivascular epithelioid cell tumors from malignant liver tumors.

CT and MRI diagnosis of hepatic epithelioid hemangioendothelioma

BACKGROUND: Hepatic epithelioid hemangioendothelioma (EHE) is a rare, low-grade malignant vascular tumor. Although its unusual imaging and pathologic findings are being recognized with increasing frequency, diagnosis is still difficult. This study aimed to analyze the CT and MRI features of hepatic EHE with a pathological study in order to improve the diagnostic accuracy and knowledge of this disease in daily practice. METHODS: Nine patients with hepatic EHE confirmed pathologically underwent plain and dynamic contrast-enhanced multi-detector row CT examination. Of these patients, four underwent additional MRI (plain Ti-weighted imaging (T1WI), T2-weighted imaging (T2WI), and dynamic contrast-enhanced scanning) and one had selective hepatic arteriography. The imaging findings were reviewed retrospectively together with the pathological results. RESULTS: A total of 79 lesions, ranging from 3.0 to 44.6 mm in maximum diameter, with an average of 16.8 +/- 7.1 mm, were found in various segments of the liver. Thirty of the 79 lesions grew adjacent to the hepatic capsule. In the 4 patients receiving MRI, 39 lesions were found with low signal intensity on unenhanced T1WI and intermediate to high signal intensity on T2WI. The 'capsular retraction' sign was found in all the 4 patients. Nine of the 39 lesions showed the 'halo' sign after contrast enhancement on MRI. Of the 79 lesions (hypodense nodules) in the 9 patients shown by unenhanced plain CT, 26 were confluent. Calcification was found in 2 patients and the 'capsular retraction' sign in 7. Thirty-eight of the 79 lesions demonstrated the 'halo' sign after contrast enhancement on CT, and this sign was more clearly demonstrated in the portal venous phase. In one patient, selective hepatic arteriography showed patchy stain in the peripheral liver parenchyma with small vessels around them. Histology in all patients revealed proliferation of abnormal fibrous tissue and vessel-like structures scattered with irregular epithelioid cells having a signet ring-like structure. Immunohistochemically, all patients were positive for CD34, 4 were positive for CD31, and 3 were positive for factor VIII-related antigen. CONCLUSIONS: Hepatic EHE may manifest as solitary or diffuse nodular lesions with a predilection for peripheral subcapsular growth and nodular confluence, together with the 'halo' and 'capsular retraction' signs. These imaging findings can help to improve the diagnostic accuracy of this rare hepatic tumor. (Hepatobiliary Pancreat Dis Int 2010; 9: 154-158)

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.

Long-term durable response to lenalidomide in a patient with hepatic epithelioid hemangioendothelioma

Epithelioid hemangioendothelioma(EH)is a rare tumor arising from the vascular endothelial cells of soft tissue or visceral organs.The most common visceral site is the liver,where it is often involved in a multifocal man-ner known as hepatic EH(HEH).Surgical resection with curative intent represents the gold standard therapy.When surgery is not feasible,or in cases of metastatic disease,no standard medical treatment is currently indicated.In small series,drugs with anti-angiogenic activity(such as bevacizumab,sorafenib,thalidomide,and lenalidomide)have been proposed with promising results.We describe a 73-year-old man with multifocal non-resectable HEH treated with lenalidomide.Disease status was evaluated by abdominal ultrasound and magnetic resonance every four months.The patient was treated for a total of 39 mo with prolonged disease stabilization and,at the time of writing,is still under treatment with a good tolerance profile.During a short period of treatment discontinuation,the disease showed slight progression that immediately resolved after the reintroduction of lenalidomide.Lenalidomide may represent a valid treatment option for HEH due to its anti-angiogenic and antineoplastic activities.This preliminary result merits further study in a large series.

Epithelioid angiomyolipoma of the liver:Cross-sectional imaging findings of 10 immunohistochemically-verified cases

AIM： To retrospectively evaluate the computed tomography （CT）/magnetic resonance imaging （MRI） imaging features of epithelioid angiomyolipoma of the liver （Epi-HAML）, with pathology as a reference. METHODS： The CT/MRI findings （number, diameter, lobar location, and appearance of lesions） in a series of 10 patients with 12 pathologically proven epithelioid angiomyolipomas of the liver were retrospectively analyzed. The imaging features, including attenuation/ signal intensity characteristics, presence of fat, hypervascular, outer rim, and vessels within lesion, were evaluated and compared with that of non-Epi- HAML in 11 patients （13 lesions）. The Fisher exact test was used to compare difference in probability of imaging features between the two types. RESULTS： For 21 patients, CT images of 15 patients and MR images of six patients were available. No patient underwent two examinations. For the 15 patients with a CT scan, all HAML lesions in the two groups （10 Epi-HAML and seven non-Epi-HAML） manifested as hypoattenuation. For the six patients with MRI, all lesions （two Epi-HAML and six non-Epi- HAML） were hypointense on TlWI （fat suppression） and hyperintense on T2WI. There were 10 non-Epi-HAML, but only two Epi-HAML lesions showed the presence of fat, which significantly different between the two types （P = 0.005）. On the dynamic contrast enhancement （DCE） imaging, eight Epi-HAML, and 13 non-Epi lesions manifested as hypervascular. Punctate or curved vessels were displayed in 10 Epi-HAML as well as in nine non- Epi lesions and outer rim enhancement could be found with eight Epi-HAML as well as six non-Epi lesions. CONCLUSION： Little or no presence of adipose tissue was found to be an imaging feature of Epi- HAML, compared with the non-Epi type. In addition, hypervascularity with opacification of central punctiform or filiform vessels on DCE would be a characteristic enhancement pattern for Epi-HAML.

Treatment and prognosis of hepatic epithelioid hemangioendothelioma based on SEER data analysis from 1973 to 2014

Background: Hepatic epithelioid hemangioendothelioma (HEH) is a rare tumor of vascular origin with an unknown etiology, a low incidence, and a variable natural course. We evaluated the management and prognosis of HEH from the Surveillance, Epidemiology and End Results (SEER) program and changes in treatment modalities of HEH over 30 years. Methods: From 1973 to 2014 in the SEER database, we selected patients diagnosed with HEH. We analyzed the clinical characteristics, patterns of management, and clinical outcomes of patients with HEH. Results: We identi ed 79 patients with HEH (median age: 54.0 years;male to female ratio: 1:2.6). The initial extent of disease was local in 22 (27.8%) patients, regional metastasis in 22 (27.8%), distant metas-tasis in 31 (39.2%) and unknown in 4 (5.1%). The median size of primary tumor was 3.85 cm (interquartile range, 2.50 7.93 cm). Among 74 patients with available management data, the most common manage-ment was no treatment (29/74, 39.2%), followed by chemotherapy only (22/74, 29.7%), liver resection-based (13/74, 17.6%), and transplantation-based therapy (6/74, 8.1%). The 5-year cancer-speci c survival rate was 57.8%. Patients who underwent surgical treatment had signi cantly higher survival than those who underwent non-surgical treatment (5-year survival;88% vs. 49%, P=0.019). Multivariate analysis revealed that surgical therapy was the only independent prognostic factor for survival (hazard ratio: 0.20, P=0.040). Conclusions: Resection or liver transplantation is worth considering for treatment of patients with HEH.

Two case reports and literature review for hepatic epithelioid angiomyolipoma: Pitfall of misdiagnosis

BACKGROUND Hepatic epithelioid angiomyolipoma(HEAML) is a rare liver disease and is easily misdiagnosed. Enhanced recognition of HEAML is beneficial to the differential diagnosis of rare liver diseases.CASE SUMMARY We presented two cases of HEAML in Changzheng Hospital, Naval Medical University, and then collected and analyzed all reports about HEAML recorded in PubMed, MEDLINE, China Science Periodical Database, and VIP database from January 2000 to March 2018. A total of 409 cases of HEAML in 97 reports were collected, with a ratio of men to women of 1:4.84 and an age range from 12 years to 80 years(median 44 years). Among the patients with clinical symptoms mentioned, 61.93%(205/331) were asymptomatic, 34.74%(115/331) showed upper or right upper quadrant abdomen discomfort, while a few of them showed abdominal mass, gastrointestinal symptoms, low fever, or weight loss. The misdiagnosis rate of HEAML was as high as 40.34%(165/409) due to its nonspecific imaging findings. Most of the tumors were solitary and round in morphology, with clear boundaries. Ultrasound scan indicated low echo with internal nonuniformity and rich blood supply in most cases. Computer tomography/magnetic resonance imaging enhanced scan showed varied characteristics. The ratio of fast wash-in and fast wash-out, fast wash-in and slow wash-out, and delayed enhancement was roughly 4:5:1. A definite diagnosis of HEAML depended on the pathological findings of the epithelioid cells in lesions and the expression of human melanoma black 45, smooth muscle actin,melanoma antigen, and actin by immunohistochemical staining. HEAML had a relatively low malignant rate of 3.91%. However, surgical resection was the main treatment for HEAML, due to the difficulty diagnosing before operation.CONCLUSION HEAML is a rare and easily misdiagnosed disease, and it should be diagnosed carefully, taking into account clinical course, imaging, pathological,and immunohistochemical findings.

Contrast-enhanced multiple-phase imaging features in hepatic epithelioid hemangioendothelioma

AIM： To investigate and review the contrast-enhanced multiple-phase computed tomography （CEMP CT） and magnetic resonance imaging （MRI） findings in patients with pathologically confirmed hepatic epithelioid hemangioendothelioma （HEHE）. METHODS： Findings from imaging examinations in 8 patients （5 women and 3 men） with pathologically confirmed HEHE were retrospectively reviewed （CT images obtained from 7 patients and MR images obtained from 6 patients）. The age of presentation varied from 27 years to 60 years （average age 39.8 years）. RESULTS： There were two types of HEHE： multifocal type （n = 7） and diffuse type （n = 1）. Tn the multifocal-type cases, there were 74 lesions on CT and 28 lesions on MRI with 7 lesions found with diffusion weighted imaging; 18 （24.3%） of 74 lesions on plain CT and 26 （92.9%） of 28 lesions on pre-contrast MRI showed the target sign. On CEMP CT, 28 （37.8%） of 74 lesions appeared with the target sign and a progressive-enhancement rim and 9 （12.2%） of 74 lesions displayed progressive enhancement, maintaining a state of persistent enhancement. On CEMP MRI, 27 （96.4%） of 28 lesions appeared with the target sign with a progressive-enhancement rim and 28 （100%） of 28 lesions displayed progressive-enhancement, maintaining a state of persistent enhancement. In the diffuse-type cases, an enlarged liver was observed with a large nodule appearing with persistent enhancement on CEMP CT and MRI. CONCLUSION： The most important imaging features of HEHE are the target sign and/or progressive en- hancement with persistent enhancement on CEMP CT and MRI. MRI is advantageous over CT in displaying these imaging features.

Hepatic epithelioid hemangioendothelioma:Update on diagnosis and therapy

With an estimated incidence of only 1-2 cases in every 1 million people,hepatic epithelioid hemangioendothelioma(HEHE)is a rare vascular endothelial cell tumor occurring in the liver and consisting of epithelioid and histiocyte-like vascular endothelial cells in mucus or a fibrotic matrix.HEHE is characterized as a low-to-moderate grade malignant tumor and is classified into three types:solitary,multiple,and diffuse.Both the etiology and characteristic clinical manifestations of HEHE are unclear.However,HEHE has a characteristic appearance on imaging including ultrasound,magnetic resonance imaging,and positron emission tomography/computerized tomography.Still,its diagnosis depends mainly on pathological findings,with immunohistochemical detection of endothelial markers cluster of differentiation 31(CD31),CD34,CD10,vimentin,and factor VIII antigen as the basis of diagnosis.Hepatectomy and/or liver transplantation are the first choice for treatment,but various chemotherapeutic drugs are reportedly effective,providing a promising treatment option.In this review,we summarize the literature related to the diagnosis and treatment of HEHE,which provides future perspectives for the clinical management of HEHE.

Hepatic epithelioid hemangioendothelioma: Dilemma and challenges in the preoperative diagnosis

Hepatic epithelioid hemangioendothelioma(HEHE) is a rare category of vascular tumor with uncertain malignant potential. It commonly presents nonspecific and variable clinical manifestations, ranging from asymptomatic to hepatic failure. In addition, laboratory measurements and imaging features also lack specificity in the diagnosis of HEHE. The aim of the present study is to highlight the dilemma and challenges in the preoperative diagnosis of HEHE, and to enhance awareness of the range of hepatobiliary surgery available in patients with multiple hepatic nodular lesions on imaging. In these patients, HEHE should at least be considered in the differential diagnosis.

Retroperitoneal perivascular epithelioid cell tumours: A case report and review of literature

BACKGROUND The perivascular epithelioid cell tumour(PEComa)family of tumours mainly includes renal and hepatic angiomyolipomas,pulmonary lymphangioleiomyomatosis and clear cell“sugar”tumour of the lung.Several uncommon tumours with similar morphological and immunophenotypical characteristics arising at a variety of sites(abdominal cavity,digestive tract,retroperitoneum,skin,soft tissue and bones)are also included in the PEComa family and are referred to as PEComas not otherwise specified.CASE SUMMARY We present a 37-year-old female patient who underwent resection of an 8.5 cm×8 cm×4 cm retroperitoneal tumour,which eventually was diagnosed as PEComa of uncertain biological behaviour.Three years after the operation,the patient remains without any evidence of recurrence.A search was performed in the Medline and EMBASE databases for articles published between 1996 and 2018,and we identified 31 articles related to retroperitoneal and perinephric PEComas.We focused on sex,age,maximum dimension,histological and immunohistochemical characteristics of the tumour,follow-up and long-term outcome.Thirty-four retroperitoneal(including the present one)and ten perinephric PEComas were identified,carrying a malignant potential rate of 44%and 60%,respectively.Nearly half of the potentially malignant PEComas presented with or developed metastases during the course of the disease.CONCLUSION Retroperitoneal PEComas are not as indolent as they are supposed to be.Radical surgical resection constitutes the treatment of choice for localized disease,while mammalian target of the rapamycin(mTOR)inhibitors constitute the most promising therapy for disseminated disease.The role of mTOR inhibitors as adjuvant or neoadjuvant therapies needs to be evaluated in the future.

Hepatic perivascular epithelioid cell tumor in three patients

Perivascular epithelioid cell tumor （PEComa） is a rare, soft tissue tumor that can occur in various locations. The present report included three patients （one male and two females; age range, 25-51 years） with hepatic PEComas. The collected data included the clinical manifestations, diagnosis, management, treatment, and prognosis. Since it is difficult to diagnose hepatic PEComas by imaging, the patients were diagnosed by tumor tissue examination such as immunohistochemistry, which was positive for HMB-45, Melan-A, and SMA on all slides. The tumor was composed of diverse tissues including smooth muscle, adipose tissue, and thick-walled blood vessels. During the follow-up period, one of the tumors was malignant （double-positive for CD34 and Ki-67） and recurred 3 months after surgery. In addition, malignant hepatic PECo- mas were reviewed in the literature, indicating that the majority of hepatic PEComas are benign, but few hepatic PEComas exhibit malignant behaviors in older female patients （〉50 years of age） with abdominal discomfort and pain, larger tumor size （〉10 cm）, or positive staining for CD34 and Ki-67. In conclusion, there is no effective method to diagnose PEComas. Currently, the diagnosis of PEComas depends on immunohistochemical staining. Tumor resection and close follow-up are the principal methods for the management of PEComas.

A perivascular epithelioid cell tumor of the stomach:An unsuspected diagnosis

Perivascular epithelioid cell tumor(PEComa) is a rare mesenchymal neoplasia and currently well recognized as a distinct entity with characteristic morphological,immunohistochemical and molecular findings.We report a case of PEComa arising in the antrum of a 71-year-old female with melena.The tumor,located predominantly in the submucosa as a well delimited nodule,measured 3.0 cm in diameter and was completely resected,with no evidence of the disease elsewhere.Histologically,it was composed predominantly of eosinophilic epithelioid cells arranged in small nests commonly related to variably sized vessels,with abundant extracellular material,moderate nuclear variation and discrete mitotic activity.No necrosis,angiolymphatic invasion or perineural infil-tration was seen.Tumor cells were uniformly positive for vimentin,smooth muscle actin,desmin and melan A.Although unusual,PEComa should be considered in the differential diagnosis of gastric neoplasia with characteristic epithelioid and oncocytic features and prominent vasculature.