You will be presented with the full text of a biomedical research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
primary biliary cirrhosis ( pbc ) is a chronic cholestatic liver disease found predominantly in middle - aged women .
although the precise pathogenesis of pbc is unclear , both b - cell and t - cell responses to the e2 subunit of the inner mitochondrial membrane pyruvate dehydrogenase complex ( pdc - e2 ) have been implicated in its pathogenesis [ 2 , 3 ] .
indeed , anti - mitochondrial antibody ( ama ) , particularly directed toward pdc - e2 , is found in most patients with pbc and has a significant value in diagnosis .
ursodeoxycholic acid is the only recommended therapy for patients with pbc with regard to longer survival . several clinical trials with immunosuppressants , such as corticosteroids or mycophenolate mofetil , failed to show clinical benefits [ 5 , 6 , 7 ] .
recently , a role for rituximab , a monoclonal antibody against human cd20 , has been suggested in the treatment for pbc ; treatment with rituximab was reported to reduce the levels of serum alkaline phosphatase ( alp ) , serum igm and ama , suggesting that rituximab may be effective in the therapy of pbc .
here , we report a female patient with pbc treated with rituximab for incidental malignant lymphoma .
after rituximab treatment , she showed improvement of serum biliary enzyme , serum igm level , ama titer and hepatic histological inflammation .
a 66-year - old woman was referred to our hospital for treatment of a gastric tumor .
she had been diagnosed with pbc at the age of 60 years and had been treated with ursodeoxycholic acid . although she had been stable and asymptomatic for several years , a gastric tumor was detected on upper gastric endoscopy performed due to abdominal discomfort after meals a month before visiting a local hospital .
abdominal computed tomography ( ct ) and 2-[f]fluoro-2-deoxy - d - glucose positron emission tomography ( fdg - pet ) showed the localized stage of malignant lymphoma in her stomach .
she showed good performance status ( ps1 ) and normal serum lactate dehydrogenase level ( 189 iu / l , normal range 121220
she had been diagnosed with gastric dlbcl with stage ii1 in the lugano classification and showed low international prognostic index ( ipi , 1 point ) . with regard to pbc status , she had no jaundice ( serum total bilirubin 1.0 mg / dl , normal range 0.21.3 mg / dl ) and showed well - preserved liver function ( serum albumin 4.0 g / dl , normal range 4.05.0 g / dl ; pt% 100% , normal range 80120% ) , although biliary enzyme levels were slightly elevated ( gamma - glutamyl transpeptidase 214 u / l , normal range 1047 u / l ; alp 826 u / l , normal range 115359 u / l ) .
her serum igm and ama - m2 titers were high ( igm 615 mg / dl , normal range 57288 mg / dl ; ama - m2 70 , normal index < 7 ) , reflecting pbc .
prior to treatment for dlbcl , we performed a biopsy on the right lobe of the liver and found chronic non - suppurative destructive cholangitis with interface hepatitis consistent with pbc at scheuer 's histological stage ii ( fig .
according to the risk score of pbc , her risk score before treatment of dlbcl was calculated as 5.5 and the estimated probability of survival for 24 months was > 99% .
thereafter , she was treated with chemotherapy , including rituximab ( r - chop  cyclophosphamide / hydroxydaunorubicin / oncovin / prednisone , rituximab 375 mg / m ) plus radiation 40 gy as shown in figure 2 .
after treatment with 8 doses of rituximab , her biliary enzyme and serum igm levels decreased gradually and the ama titer also decreased ( fig .
thereafter , she was observed and remained in a stable condition for 24 months after diagnosis of dlbcl .
she was asymptomatic and her pbc mayo risk scores remained low for 24 months after diagnosis of dlbcl ( fig .
2 ) . however , she showed marked jaundice and ascites without elevation of serum ama titer 30 months after diagnosis of dlbcl .
ct scan showed bile duct cancer at the bottom of the common bile duct in addition to cirrhotic changes such as ascites .
percutaneous drainage of the bile duct was immediately and successfully performed and her jaundice was partially decreased , but surgical resection or chemotherapy could not be done due to decreased liver function .
hepatobiliary scintigraphy using tc - pmt showed disturbance of hepatocellular excretion of bile ( data not shown ) .
therefore , her cirrhosis was estimated to be already established at the time when jaundice developed .
she received the best supportive care and died from liver failure 3 years after diagnosis of dlbcl .
3a , b , scheuer 's histological stage iv ) and lower bile duct cancer .
pbc is a chronic cholestatic liver disease predominant in middle - aged women , and no recommended therapy other than ursodeoxycholic acid has been reported . recently , the anti - cd20 monoclonal antibody rituximab was suggested as a treatment option for pbc [ 8 , 11 ] .
biological and immunological improvements , such as of biliary enzyme , serum igm and serum ama titer , have been reported [ 8 , 11 ] .
in addition to biological and immunological improvements in the case presented here , histological inflammation was also improved after rituximab treatment .
our results demonstrated the histological effectiveness of rituximab for liver inflammation and may support the effectiveness of rituximab as a treatment option for pbc .
however , our case showed rapid progression to cirrhosis within a short time without remarkable elevation of biliary enzymes or ama titer ( fig .
the mayo risk scores of our case had remained relatively low until 24 months after diagnosis of dlbcl . the cirrhosis in this case was therefore estimated to have been established within a short time .
first , the controversial effect of rituximab should be discussed . in previous studies in animal models ,
b - cell depletion with anti - cd20 antibody had been shown to exacerbate cholangitis , and the authors recommended care regarding application of anti - cd20 antibody therapy against pbc in humans . in a previous human study of rituximab , serum igm or inflammatory cytokine seemed to be increased in a proportion of cases .
serum igm was also increased transiently in our case , suggesting a conflicting effect of cessation of rituximab treatment .
in addition , the elevation of transforming growth factor beta ( tgf- ) mrna in cd4 + t - cells after treatment of pbc was reported .
although tgf- was not evaluated in the present case , careful observation might be considered after treatment with rituximab for pbc .
second , the patient had been treated with chop and radiation in addition to rituximab . chop and radiation therapy may induce fibrosis at the site of radiation .
however , the site of radiation in our case was the stomach , which was different and distant from the liver . in the present case , there were no increases in biliary enzyme levels during either chop or radiation therapy , and the time after chop and radiation therapy was relatively short ( fig .
thus , it seems unlikely that the observed effects were due to chop and radiation .
third , the possibility that obstructive jaundice due to bile duct cancer induced fibrosis of the liver should be discussed .
, successful bile duct drainage had been performed in our case . in our case ,
hepatobiliary scintigraphy using tc - pmt suggested disturbance of hepatocellular excretion of bile rather than obstruction of the lower bile duct .
furthermore , cirrhotic changes such as ascites or hypoalbuminemia had already been found when her bile duct cancer had been detected first .
bile duct inflammation improved biochemically , immunologically and histologically after rituximab treatment , suggesting that rituximab may be a useful treatment option for pbc . as the precise mechanism of fibrosis progression in our case remained unclear , careful observation is required after the administration of rituximab for treatment of pbc .
primary biliary cirrhosis ( pbc ) is a progressive liver disease for which limited therapies are recommended . 
 rituximab , an anti - cd20 monoclonal antibody , is expected to be a useful therapeutic regimen for pbc . 
 previous studies indicated biochemical and immunological improvement in pbc after rituximab treatment . 
 although rituximab shows therapeutic potential for pbc , few cases have been reported and histological improvement and long - term outcome remain uncertain . here , we report a case of pbc in a 66-year - old japanese female patient who presented with a gastric lymphoma and who had been treated with a regimen containing rituximab for incidental malignant lymphoma . 
 she showed biochemical and immunological improvements , and liver histology before and after rituximab treatment confirmed a decrease in liver inflammation . 
 however , she developed liver cirrhosis a short time after rituximab treatment without biochemical or immunological worsening . 
 rituximab treatment for pbc might be considered and careful observation is required after treatment .