the number of patients with ulcerative colitis ( uc ) has been increasing in japan , and recently , colitis - related cancer has attracted much attention ( 1 - 3 ) . the risk of developing cancer is higher in patients with long - term morbidity due to uc . we experienced a rare colonic tumor that was difficult to differentiate from cancer in a patient with long - standing uc . a 51-year - old woman who had been experiencing frequent bloody mucosal diarrhea was diagnosed with uc involving the entire colon in 1978 . since the diagnosis , she maintained a state of remission for 30 years with while only being adminstered oral 5-aminosalicylic acid . surveillance colonoscopy was regularly performed , and an elevated tumor measuring 15 mm in diameter with a small ulceration was noted in the descending colon in july 2011 ( fig . 1 ) . 
 colonoscopy shows an elevated tumor with an unclear boundary and small ulceration in the descending colon . we performed biopsies of the tumor , including a boring biopsy , but all biopsy findings demonstrated mildly inflamed colonic mucosa with regenerative changes . neither any neoplasm nor dysplasia was detected . the laboratory blood test showed no abnormalities , including tumor marker levels , such as carcinoembryonic antigen and carbohydrate antigen 19 - 9 , except for a slight elevation in the c - reactive protein level ( 1.4 mg / dl ) . the tumor gradually progressed to resemble type-2 cancer after 14 months of observation ( fig . 2 ) . abdominal computed tomography images revealed a tumor measuring from 20 - 30 mm in diameter in the descending colon , but no enlarged lymph nodes or metastases were detected . endoscopic ultrasonography revealed that the tumor was located mainly in the submucosal layer , and the muscle layer was compressed ( fig . we considered the possibility of colitis - related cancer and recommended surgical resection , but the patient rejected this . a pathological examination detected no cancer cells , despite the continued growth of the tumor after 18 months ( fig . a contrast enema showed a smoothly elevated lesion with a central depression in the descending colon . endoscopic ultrasonography shows a tumor of the submucosal layer , and the compressed muscle layer ( a ) . the tumor demonstrates growth similar to type 2 cancer ( b ) . 
  in march 2013 , the patient finally agreed to undergo surgery and received a laparoscopic partial resection of the descending colon . the gross appearance and low - power magnification of the specimen showed a protruded transmural tumor with ulceration ( fig . the tumor was mainly composed of spindle cells having eosinophilic cytoplasm and cigar - shaped nuclei with a blunt end ( fig . immunohistochemical staining was positive for the conventional smooth muscle markers of -smooth muscle actin and desmin , and entirely negative for c - kit , dog-1 , cd34 , and s-100 ( fig . the background colonic mucosa was edematous and accompanied with mild to moderate chronic inflammatory cell infiltration . after surgery , no recurrence or metastasis has been detected thus far ( october 2015 ) . the elevated tumor which resembles type-2 cancer measures 4.03.2 cm in size ( a ) . low - power magnification of the specimen stained with hematoxylin and eosin staining ( h&e , 1 ) showing the transmural tumor with an ulcerated superficial mucosa ( b ) . 
 
 pathological examinations of the tumor mainly composed of spindle cells having eosinophilic cytoplasm and cigar - shaped nuclei with a blunt end ( hematoxylin and eosin staining , 200 ) . immunohistochemistry showing that the tumor is positive for -smooth muscle actin ( a ) and desmin ( b ) , and negative for c - kit ( c ) , dog-1 ( d ) , cd34 ( e ) , and s-100 ( f ) ( 40 ) . patients with uc are known to be at an increased risk of developing colorectal adenocarcinoma ; however , non - epithelial malignancies are uncommon . among non - epithelial tumors associated with inflammatory bowel disease , there have only been two reported cases of lms in uc ( table ) ( 4,5 ) and five cases of sarcomas associated with crohn 's colitis as far as we searched pubmed with term  inflammatory bowel disease and leiomyosarcoma  . the two reported cases of lms in uc showed active colitis , uncontrolled bleeding , and polypoid tumors . our case had minimal activity of uc with no symptoms and a tumor with a type-2 cancer - like appearance . the recent classification of mesenchymal tumor differentiates lms from gastrointestinal stromal tumors as a newly defined disease entity . agaimy and wnsch reported only three cases ( 1.1% ) of lms among 262 cases of gi mesenchymal lesions at their institution during a 12-year period ( 6 ) . yamamoto et al . clinicopathologically reviewed 55 reported cases of lms in the gi tract , and found 25 small intestinal , 21 large intestinal , 5 gastric , and 4 esophageal tumors ( 7 ) . the association of lms with uc is not described in these papers , and its exact incidence is unclear . however , chronic inflammation is suggested to be a risk factor for testicular lms in some case reports ( 8 - 11 ) , and further study may thus be needed to reveal the causal relationship between lms and chronic bowel inflammation . the differential diagnosis for lms must include submucosal tumors such as lymphoma , gastrointestinal stromal tumor ( gist ) , and inflammatory fibroid polyp ( 12 ) . the endoscopic findings of lymphoma and gist are varied , but a pathological diagnosis may be possible with an appropriate biopsy . inflammatory fibroid polyps form erosion and ulcers in the elevated mucosal surface and show an onion skin appearance on biopsy . metastatic tumors of the colon that are most often found in gastric cancer and endometriosis that can occur in the rectum and sigmoid colon are rarely associated with an ulcer . an accurate diagnosis of submucosal tumors by biopsy is often difficult , and as a result , surgery is needed . pre - neoplastic lesions and invasive cancers associated with uc usually develop as multiple and superficially extended lesions called dysplasia - associated lesions or masses ( dalm ) ( 13 ) , and patients with cancer or dalm are recommended to undergo prophylactic proctocolectomy with an ileoanal pouch ( 14 ) . the endoscopic findings of uc - related neoplasias are so varied that morphological classification is difficult ( 15 ) . a retrospective multi - institutional questionnaire survey ( 16 ) found reddish and elevated tumors with obscure boundaries in 70% of patients with uc - related neoplasias . in the present case , however , the boundary of the tumor was clear , and neither dysplasia nor cancer was observed in the biopsy specimens . therefore , we performed a partial colectomy and could correctly diagnose the lms by a detailed pathological examination . the reported clinical features of lms in the gi tract are polypoid and intramural types that can arise from either the muscularis mucosae or propria ( 6,17 - 19 ) . grossly , they resemble type-2 cancer , presenting with elevated and ulcerated tumors with transmural involvement ( 7 ) , as was observed in this case . in most cases , the endoscopic and radiologic features are nonspecific ; therefore , it is difficult to diagnose lms preoperatively ( 20,21 ) . lymphogenic spread is rare , and it is unnecessary to perform lymph node dissection for this tumor ( 6,18 ) . neighboring tissue invasion and liver metastases are common , and the prognosis of lms is generally poor . tumor larger than 5 cm in size significantly correlate with a shorter overall survival time ( 7 ) . our patient had a tumor measuring less than 5 cm in size and no metastasis , and she has survived with no recurrence for 2.5 years after surgery . we herein reported a case of colonic lms in an uc patient that was difficult to differentiate from a colitis - related cancer . although its incidence in association with uc appears to be extremely rare , the possibility of lms should be considered when a nonspecific tumor with repeatedly cancer - negative biopsy findings is found .
ulcerative colitis ( uc ) is known to be associated with an increased risk of colorectal cancer . however , the occurrence of non - epithelial malignancies is uncommon . 
 an elevated lesion in the descending colon was found in a 51-year - old woman with a 30-year history of uc . despite tumor progression 
 , repeated biopsies showed no cancerous findings . because the lesion was highly suspected to be a malignant tumor , 
 a partial colectomy was performed . 
 the pathological diagnosis was leiomyosarcoma . 
 leiomyosarcoma of the gastrointestinal tract is rare , and this is only the third known case reported in patients with uc .