when fibrosarcoma is diagnosed during the early years of life , it is called congenital infantile fibrosarcoma ( cif ) , representing less than 1% of all pediatric malignant tumors ( 1 , 2 ) . in contrast with adult fibrosarcoma , infantile fibrosarcoma ( if ) rarely exhibits distant metastasis and has a good prognosis ; greater than 90% of patients may be cured with appropriate management . the tumor usually occurs in soft tissues of the extremities and is often asymptomatic . in such cases , rarely , if may occur in the gastrointestinal tract ; a few cases of gastrointestinal fibrosarcoma have been reported in the literature . necrotizing enterocolitis ( nec ) , which is a primary intestinal wall pathology , has been cited as the major cause of pneumoperitoneum in most published literatures ( 3 , 4 ) . however some conditions , not affected by a primary pathology of intestinal wall itself ( e.g. intestinal atresia , stenosis , meconium ileus , colonic aganglionosis or volvulus ) , may lead to neonatal pneumoperitoneum . this case was a pneumoperitoneum not associated with a nec also . in this report , we present an extraordinary case of cif of the sigmoid colon causing pneumoperitoneum in a newborn baby . a 2-day - old korean boy , delivered at 37 weeks by cesarean section owing to fetal bradycardia , with a birth weight of 3,420 g , was referred to the neonatal intensive care unit in pusan national university children 's hospital because of abdominal distension and free air in the peritoneal cavity at may 1st , 2011 . a plain abdominal radiograph showed normal air - filled loops of bowel ; however a large amount of free air occupied the central portion of the abdomen ( fig . 1 ) . the patient underwent an emergency laparotomy on the day of admission to the neonatal intensive care unit . a large amount of bile - stained a round mass , about 5 cm in diameter , was observed in the left lower abdominal cavity , and it seemed to wrap around a loop of sigmoid colon ( fig . pathologic analysis report described an infantile fibrosarcoma , measuring about 4.7  2.8 cm , involving mainly the submucosa and muscularis propria with an infiltrative growth pattern ( fig . the immunohistochemical stain of the tumor was positive for vimentin and sma , and negative for h - caldesmon , s-100 , cd34 , c - kit , desmin , and alk-1 ( fig . 4 ) . the ki-67 proliferation index was 20% . because complete surgical resection was performed and the surgical resection margins were free tumor , the patient was observed without adjuvant therapy . fibrosarcoma is a tumor that arising from mesenchymal cells and composed of malignant fibroblasts within a collagen background . after infantile fibrosarcoma first recognized in 1962 ( 5 ) , it has been generally studied . congenital infantile fibrosarcoma ( cif ) is a very rare type of nonrhabdomyosarcoma soft - tissue sarcomas , usually occurring in the 1st year of life , with approximately 40% of lesions present at birth and more than 80% diagnosed within 1 yr ( 6 ) . it accounts for 5%-10% of all soft - tissue sarcomas in infants younger than 1 yr and is slightly more common in boys ( 7 , 8) . in contrast with adult fibrosarcoma , infantile fibrosarcoma ( if ) is considered a low - grade malignant tumor and carries an excellent prognosis , with survival rates of 80%-90% ( 9 ) . if is usually located in subcutaneous tissues at various anatomic sites , most frequently involving the extremities and the axial regions . especially in older children , if less frequently involves the trunk , head and neck ( 6 ) . the manifestation of infantile fibrosarcoma in the reported cases is generally a painless swelling , exhibiting steady growth . however , it may rarely involve the retroperitoneum , mesentery , mouth , presacral region , lung , or gastrointestinal tract . a few cases have been reported recently about if involving the gastrointestinal tract ( e.g. , the duodenum , jejunum , ileum , and hepatic and splenic flexures of the colon ( 10 - 12 ) . intestinal obstruction or meconium peritonitis due to bowel perforation was the primary manifestation in the reported cases involving intestine . in our patient , pneumoperitoneum was the presenting problem , but there were no gross findings at surgery implying a definite perforation of the colon or rupture of the mass ; neither was there any ischemic change or obstruction , or apparent necrosis of the tumor on histologic examination . we found no obvious explanation for the large amount of free - air in the peritoneal cavity seen on radiologic examination prior to surgery ; we assume that a sealed - off microperforation was responsible for the condition . pneumoperitoneum in neonates accounts for about 1% of total admission at a neonatal intensive care unit . most cases occur in relation to a primary intestinal wall pathology such as necrotizing enterocolitis ; however , pneumoperitoneum may rarely be associated with intestinal atresia , stenosis , meconium ileus , colonic aganglionosis , or volvulus . it is necessary to distinguish if from other stromal tumors , particularly in cases involving the gastrointestinal tract . . molecular biological analysis may be useful when identifying the presence of specific transcription errors , e.g. , the evt6-ntrk3 translocation , but it is not always used ( 6 , 9 , 11 ) . surgical excision remains the principal component of treatment , showing a good result when complete resection with tumor - free margins is achieved . there is no defined role for adjuvant chemotherapy or radiotherapy after complete surgical excision ( 9 , 13 ) . the prognosis is generally favorable with more than 90% long - term survival ( 9 ) . in our patient , we could not identify any evidence of local recurrence or distant metastasis during a 1-yr follow - up period . in conclusion , cif of the sigmoid colon is a rare soft tissue tumor , with a favorable outcome likely after appropriate surgical resection . it may present with bowel perforation in the early neonatal period ; therefore a neonatal pneumoperitoneum not related to necrotizing enterocolitis requires attention for management .
congenital infantile fibrosarcoma ( cif ) is a rare soft - tissue tumor in the pediatric age group and seldom involves the gastrointestinal tract . 
 a 2-day - old boy was transferred to our hospital with a pneumpoperitoneum . 
 after emergency operation , we could find a solid mass wrapping around a sigmoid colon and performed a segmental resection of sigmoid colon including a mass . 
 histopathologic examination showed an infantile fibrosarcoma origining from the muscular layer of colon . 
 the baby was discharged on the 17th hospital day and followed for 1 yr without recurrence .