a 60-year - old man was referred to our outpatient clinic because of persistent air leakage lasting 17 days from his chest tube , which had been inserted for empyema at another hospital .
he had a past history of diabetes mellitus and tuberculous pleuritis treated with antituberculous medicine 30 years ago .
he had not been treated previously for empyema by drainage procedures such as closed thoracostomy , percutaneous catheter aspiration , or drainage .
a chest computed tomography ( ct ) scan showed loculated pleural fluid collection with air density and pleural wall thickening with enhancement and calcification .
further , a 2.2-cm mass - like lesion adjacent to the margin of an empyema cavity was identified retrospectively ( fig .
laboratory tests revealed a slightly elevated c - reactive protein level of 1.0 mg / dl , while other parameters were within the normal range .
seven days after admission , we planned decortication because of prolonged air leakage and the patient s desire for surgery .
the fibrinous contents of the empyema cavity were removed , and the lung was decorticated without difficulty .
therefore , the operation was completed after the confirmation of the full expansion of the lung .
contrary to our expectations , however , the histopathological diagnosis after the operation was malignant lymphoma .
immunohistochemically , the tumor cells were positive for leukocyte common antigen , cd79a , ki-67 ( range , 7080% ) , and cd3 , and negative for cd20 .
2 ) . after the identification of a monoclonal proliferation of b - cells by an immunoglobulin heavy- chain gene rearrangement
, the final diagnosis of diffuse large b - cell lymphoma with an aberrant expression of a t - cell marker was made .
the postoperative period was uneventful , and the chest tube was removed on postoperative day 12 .
we considered the possibility of incomplete resection , and the patient was referred to the hematology department for adjuvant chemotherapy .
pyothorax - associated lymphoma ( pal ) is a rare malignant lymphoma developing in the pleural cavity after long - standing pyothorax . according to the current world health organization histological classification published in 2005
, pal is defined as  a neoplasm of large b - cells , typically with immunoblastic morphology , usually presenting as a pleural mass. it occurs in patients with a history of long - standing pyothorax resulting from pulmonary tuberculosis or tuberculous pleuritis and is strongly associated with the epstein  barr virus ( ebv ) .
a majority of these cases have been reported in japan , although some cases have occurred in western countries .
it is assumed that the higher prevalence in japan is caused by a higher incidence of ebv infection and lung collapse therapy for tuberculosis in asia , particularly in japan .
the etiology of pal is not clearly understood . however , previous reports have suggested that artificial pneumothorax , ebv latent infection , cytokines such as interleukin-6 and -10 , and oxidative stress produced during chronic inflammation might be important factors for pal development .
reported a summary of clinical and pathological findings in 106 patients with pal in japan .
the median age of the patients was 64 years ( range , 46 to 82 years ) with a male / female ratio of 12.3:1 .
the interval between the onset of pleuritis and the initial symptoms of lymphoma was 37 years ( range , 20 to 64 years ) .
all of the cases were of non - hodgkin s lymphoma , among which the diffuse large b - cell type was the most common ( 88% ) .
the definitive diagnosis of pal can be made by histopathological and immunohistochemical examinations of biopsy or surgically resected specimens .
a typical histological examination demonstrates a diffuse destructive proliferation of large cells with a predominant population of immunoblasts .
lymphoma cells are mostly positive for cd20 and cd79a in the immunohistochemical examination . according to the pathological findings by aozasa et al .
, a majority of the cases were cd20 + and/or mbi+ , cd45ro- , and cd3- , and were of the b - cell lineage .
however , there could be an aberrant phenotype with the expression of some t - cell markers , as in our case .
ueda et al .   analyzed the radiological features of pal to help in the diagnosis of this rare malignant lesion .
they reported that a typical radiological finding of pal was a pleural soft - tissue mass adjacent to the margin of a coexistent empyema cavity and the shape of the mass demonstrated on the ct scan was mostly lenticular or crescentic .
we were able to find a mass - like lesion on the ct scan retrospectively by reviewing the report of ueda et al .
although the optimal treatment is not well - established , most patients with pal have received chemotherapy and/or radiotherapy , as reported in the literature .
the prognosis of pal reported in 2002 is poor , with a five - year survival rate of 21.6% , although a better survival rate is observed in patients who are responsive to chemotherapy .
however , a recent survey reported an improved overall five - year survival rate of 35% and suggested several prognostic factors for the overall survival . in summary
, we have reported a case of pal of a b - cell origin resulting from tuberculous pleuritis .
although pal is a relatively rare disease , it should be considered a potential diagnosis in patients with a history of chronic pyothorax .
 pyothorax - associated lymphoma is a relatively rare type of lymphoma that occurs in patients who have long histories of tuberculous pleuritis or induced pneumothorax . 
 it is a type of non - hodgkin s lymphoma of mainly the b - cell phenotype and is strongly associated with epstein  barr virus infection . 
 a majority of these cases have been reported in japan , although some cases have occurred in western countries . here 
 , we describe a case of pyothorax - associated lymphoma in a patient with a 30-year history of chronic tuberculous empyema . 
 the patient underwent decortication under the impression of chronic empyema with fistula . 
 the histopathologic diagnosis was a diffuse large b - cell lymphoma associated chronic inflammation . 
CASE REPORT
DISCUSSION