the perivascular epithelioid cell tumors ( pecomas ) are a family of related mesenchymal neoplasms that include angiomyolipoma , lymphangiomyomatosis , and clear cell ' sugar ' tumor of the lung ( 1 ) . in 1991 ,
investigations of hmb-45 ( gp100 ) immunoreactivity and the presence of premelanosomes in both clear cell ' sugar ' tumors ( ccsts ) of the lung and the epithelioid clear cell component of angiomyolipoma ( aml ) of the kidney and liver were published ( 2 - 6 ) .
first proposed a cellular link among these unusual mesenchymal lesions and lymphangiomyomatosis ( lam ) ( 7 ) . soon after , the same group suggested the descriptive term ' perivascular epithelioid cell ' ( pec ) for the distinctive cell type found in these three lesions , and hypothesized that pecs may originate from the walls of blood vessels based on the observation that these cells are frequently and intimately related to such structures ( 8) .
most of the patients with lesions of the pecoma family are female , and some patients also show coexistence of the tuberous sclerosis complex ( tsc ) ( 9 ) .
although there are strong associations between the tsc , aml , and lam , this association is much less clear for the rare pecomas ( 10 ) .
malignant pecomas are extremely rare , and they have been reported to occur in the uterus , broad ligament , prostate , small intestine , rectum , skull base , and heart ( 11 - 16 ) .
a 30-yr - old korean man visited to hospital for the evaluation of a growing palpable abdominal mass , which he had felt growing over 6 months .
a computed tomography ( ct ) scan of the abdomen showed an intraabdominal mass with a size of about 7.5 cm that was supposed to originate from the falciform ligament .
the solid portion was yellow - brown in color and revealed foci of hemorrhage and necrotic changes ( fig .
histological examination showed sheets of spindle - to - epithelioid cells with clear - to - eosinophilic cytoplasm ( fig .
they were also positive for the s-100 , a marker of neurogenic and melanocytic tumors , and were negative for the cd117 ( c - kit ) , which typically shows positivity in classic gastrointestinal stromal tumors ( gists ) .
the tumor cells were also negative for factor viii , cd34 , cd31 , ck , and desmin . however , the tumor showed high cellularity and necrotic foci .
these features suggest that the tumor had aggressive potential and a high probability of local recurrence or metastasis .
the ki-67 proliferative index was approximatively 15 percent of cells . at 6 days after surgical excision ,
because the biological behavior of this tumor is still unclear , with descriptions in the literature of pecomas with metastases , we had planned follow - up investigation in the form of ct scans of the abdomen and the thorax . until now
the " perivascular epithelioid cell " ( pec ) was first proposed by bonetti and colleagues in 1992 as an explanation for the presence of hmb-45 ( gp100 ) immunoreactivity and premelanosomes in both clear cell " sugar " tumors of the lung and angiomyolipomas ( 8) .
the pecs are characterized by epithelioid cells with a clear to faintly eosinophilic cytoplasm , a perivascular location , and the unique co - expression of smooth muscle actin isoforms and melanocytic markers such as the gp100 protein recognized by hmb-45 ( 8) .
hmb-45 and melan - a are the most sensitive melanocytic markers in pecoma . on our case ,
tumor cells were positive for hmb-45 , sma , and s-100 . at the time of the final diagnosis , no metastatic lesions were present .
a significant association was noted between a tumor size of 8 cm ( median size ) , mitotic activity greater than 1/50 hpf , and necrosis with aggressive behavior ( 1 ) .
patient age ( median age : 46 yr ) , infiltrative growth pattern , gynecologic primary site , high cellularity , high nuclear grade , atypical mitotic figures , vascular invasion , and the growth pattern of the tumor ( spindled or epithelioid ) were not associated with aggressive behavior ( 1 ) . in our case , the tumor size was 8.0 cm .
these features suggested that the tumor had aggressive potential and a high probability of local recurrence or metastasis .
the ki-67 proliferative index was approximately 15 percent of cells . although it has been suggested that pecomas do not express s-100 protein , thereby allowing them to be distinguished from melanoma and clear cell sarcoma , this was not the case .
a series of seven very young patients ( age range , 3 - 29 , median , 11 yr ) pecoma of the falciform ligament / ligamentum teres was reported in 2000 .
therapy consisted of surgical resectioning . during the mean follow - up of 18 months ( range , 6 months to 5 yr ) in six of seven cases , five patients remained healthy , and
relatively few malignant pecomas have been reported , firm criteria for malignancy have yet to be established .
special attention should be paid to the lungs and liver because of potential metastasis ( 18 ) .
a pecoma situated elsewhere has to be excluded because the tumor described here could have been a primary tumor or a metastasis . because pecomas can behave in an aggressive manner , careful follow - up is warranted .
in addition , to perform a pathological diagnosis , recognition of the clinicopathological , histological , and immunohistochemical ( hmb-45 positive ) features of pecoma seems to be very important .
 we present a case of perivascular epithelioid cell tumors ( pecomas ) in the abdominal cavity at the falciform ligament . 
 a 30-yr - old korean man visited to hospital for the evaluation of a growing , palpable abdominal mass . 
 he had felt the mass growing over 6 months . 
 there was no family or personal history of tuberous sclerosis . 
 the resected specimen showed a mass of 8.07.05.5 cm in size . 
 histological examination showed sheets of spindle - to - epithelioid cells with clear - to - eosinophilic cytoplasm . 
 immunohistochemically , tumor cells were positive for hmb-4 ( gp100 ) and smooth muscle actin . 
 they were also positive for the s-100 , which is a marker of neurogenic and melanocytic tumors . 
 patient was treated with radical resection of tumor without any adjuvant therapy . 
 he is well and on follow - up visits without tumor recurrence . 
INTRODUCTION
CASE REPORT
DISCUSSION