lymphoblastic lymphoma ( lbl ) is a highly aggressive subtype of non - hodgkin 's lymphoma ( nhl ) , and it accounts for about 2% of all nhls .
the majority of acute lymphoblastic leukemias ( alls ) are of the immature b - cell phenotype , whereas approximately 90% of lbl are of the immature t - cell phenotype [ 2 , 3 ] . the natural history of b - lbl has not been well defined , and molecular studies are lacking because the literature is limited to small series and case reports .
however , it is known that b - lbl has a predilection for children . in 1 study , a review of previous literatures reporting b - lbl in 105 patients , 64% ( 63 of 98 ) of patients for whom the age at diagnosis was available were younger than 18 years . in korea ,
the incidence of b - lbl has been reported to be 11.6% ( 42 of 360 cases ) in children with nhl , and only 0.12% ( 1 of 802 cases ) in adults with nhl .
patients with b - lbl mostly present with extranodal involvement sparing the bone marrow [ 4 , 7 ] . the most affected sites are skin ( 33% ) , lymph node ( 22% ) , bone ( 19% ) , and mediastinum ( 5% ) .
although skin is the most affected site , primary involvement of the skin is a rare manifestation of b - lbl because cutaneous b - lbl usually presents secondary to systemic nodal b - lbl [ 8 , 9 ] .
here we report a 78-year - old man with a single cutaneous lesion of b - lbl at diagnosis .
in september 2009 , a 78-year - old man visited the seoul veterans hospital with a dark red - colored mass on the right upper quadrant , which he had had for several months .
the mass was approximately 5060 mm in size , non - tender , non - itching , and round , and had a smooth surface ( fig .
there were no palpable enlarged lymph nodes or any other skin lesions in any region , including the neck , axilla , and groin .
he was subsequently transferred to the korea cancer center hospital for a further work - up .
a complete blood count revealed normal values , as follows ; white blood cell count , 6.7810/l ; platelet count , 24310/l ; and hemoglobin , 14.0 g / dl .
u / l ( normal range , 4 - 43 u / l ) , alanine transaminase , 15 u / l ( normal range , 8 - 38 u / l ) ; uric acid , 6.7 mg / dl ( normal range , 3.4 - 7.0 mg / dl ) ; lactate dehydrogenase , 286 u / l ( normal range , 240 - 480 u / l ) ; and alkaline phosphatase , 57 u / l ( normal range , 40 - 129 u / l ) . computed tomography ( ct ) of the chest showed normal findings .
however , abdominal and pelvic ct scans depicted a 4-cm sized , discoid , highly attenuating mass in the skin of the right upper aspect of the abdomen without demonstrably enlarged lymph nodes .
f - fluorodeoxyglucose ( fdg ) positron emission tomography ( pet)/ct visualized a single hypermetabolic lesion in the abdominal wall ( standardized uptake value [ suv]=12.8 ) ( fig . 1c ) . a microscopic examination of the biopsied specimen revealed small malignant cells with fine chromatin , convoluted nuclear membranes , and scant cytoplasm infiltrating the dermis ( fig .
staining , atypical cells showed positivity for b - cell lineage markers ( cd79a , paired box 5 [ pax5 ] , and precursor lymphoblastic marker ( terminal deoxynucleotidyl transferase [ tdt ] ) ( fig .
for staging , bilateral bone marrow ( bm ) and diagnostic spinal tapping ( for cerebrospinal fluid [ csf ] cytology ) were performed .
on the basis of the pathological diagnosis and clinical staging , he was diagnosed as having primary cutaneous precursor b - lbl , ann arbor stage iea ( only localized , single extranodal site involvement ) .
he was treated using the cyclophosphamide , adriamycin , vincristine , and prednisolone ( chop ) regimen ( cyclophosphamide , 750 mg / m ; adriamycin , 35 mg / m ; vincristine , 1.4 mg / m [ maximum 2 mg ] i.v . on day 1 ; and prednisolone , 100 mg p.o . on days 1 - 5 ) , which is not an intensive multi - agent chemotherapy , because of his advanced age .
for the same reason , the dose of adriamycin in the standard chop regimen was reduced from 50 mg / m to 35 mg / m . after the 1st chop cycle , the mass shrank and had a flattened surface , and after the 3 cycle , the tumor disappeared by gross examination ( fig .
furthermore , f - fdg pet / ct failed to depict a hypermetabolic lesion in the abdomen .
we concluded that he had achieved complete response ( cr ) after 3 cycles of chop therapy .
an additional chop cycle was then administered and the initial skin lesion site was subjected to 3,600 cgy of radiotherapy over 4 weeks . at 21 months after completing 4 cycles of chop treatment and radiotherapy , the patient was found to have maintained a state of cr .
primary cutaneous b - lbl involving only the skin without systemic disease appears to occur almost exclusively in children or young adults , and is extremely rare in older patients [ 7 , 10 ] .
furthermore , it appears to be predominantly located in the head and neck region [ 9 , 10 ] .
thus , the present case report of a single cutaneous lesion of b - lbl in the abdominal wall in a 78-year - old patient expands our knowledge of this disease . for a differential diagnosis ,
comprehensive ihc staining is crucial , but no single diagnostic immunohistologic pattern has been established for b - lbl . nevertheless , certain immunophenotypic patterns can help distinguish malignant lymphomas and benign lymphoid proliferations . the work - up for
the differential diagnosis of b - lbl includes small , blue , round cell tumors , e.g. , ewing 's sarcoma , merkel 's cell carcinoma , neuroblastoma , rhabdomyosarcoma , wilm 's tumor , neuroendocrine carcinoma , and metastatic small cell carcinoma , as well as other lymphoid malignant neoplasms .
b - lymphoblasts are positive for cd10 , surface cd22 , cd24 , pax5 , and tdt in most cases , while the expression of cd20 and cd34 is variable . in tissue sections , cd79a and pax5
are most frequently used to demonstrate b - cell differentiation , but the former reacts with some cases of t - all and , thus , is not specific . in the present case ,
small malignant cells were positive for lca , tdt , cd79a , pax5 , and bcl-2 , but negative for cd20 , cd10 , and cd3 .
these immunohistochemical findings were consistent with precursor b - lbl , although the cells were negative for cd20 and cd10 .
patients with b - lbl respond well to intensive multi - agent chemotherapy ( all - type regimens or intensive nhl - type regimens ) [ 4 , 13 ] . according to some reports ,
adult patients with b - lbl seem to have better cr rates and longer response duration than those with acute b - lbl treated with similar regimens .
in addition , it has been suggested that survival is better for b - lbl than t - lbl .
primary cutaneous and extracutaneous b - lbl are not different in the managements ; both conditions should be treated with intensive chemotherapy regardless of the staging results [ 4 , 7 , 13 ] .
however , our case was treated using the chop regimen because of his far advanced age .
morel et al . reported treatment outcomes by different treatment protocols in 80 adult patients with lbl . in that study ,
the cr rate with chop was 71% compared to 83% with the intensive nhl protocol ( lnh-84 ) and 86 - 91% with 2 different all protocols ( lala or fralle ) .
however , there was no significant difference in cr rate and cr duration among the regimens .
in addition , there was no significant difference between the chop and lnh-84 protocols in overall survival of ann arbor stage i to iii patients ( 2-year survival , 62% and 74% , respectively ; p=0.49 ) .
on the basis of the results demonstrated by morel et al . , we suggest that the chop regimen can be a reasonable second option in elderly patient who would not tolerate standard intensive regimens for lbl . the prognosis of patients with cutaneous lbl appears to be similar to that of patients with extracutaneous lbl .
some authors have reported that a proportion of patients without systemic disease at diagnosis might progress to advanced disease with systemic involvement , most commonly to precursor b - all over a period of days to months .
these reports suggest that primary cutaneous precursor b - lbl has the potential to progress without adequate systemic chemotherapy , and thus , cutaneous infiltrates might be an early manifestation of precursor b - lbl / lymphoma progression to diffuse disease . in conclusion , we report a case of b - lbl presenting with a single cutaneous lesion without systemic involvement in an old man .
this case suggests that the possibility of primary cutaneous b - lbl among several subtypes of cutaneous lymphomas be considered despite its rarity , when an adult patient presents with only skin involvement and has pathological findings compatible with lymphoma .
 precursor b - cell lymphoblastic lymphoma ( b - lbl ) is an uncommon high - grade neoplasm of immature b cells . 
 it occurs predominantly in childhood with extranodal involvement such as skin and bone . 
 therefore , primary cutaneous involvement in elderly adults is a very rare manifestation of b - lbl . here 
 , we report a 78-year - old man with b - lbl presenting as a single cutaneous lesion which was immunohistochemically positive for leukocyte common antigen ( lca ) , cd79a , paired box 5 ( pax5 ) , b cell lymphoma-2 ( bcl-2 ) , and terminal deoxynucleotidyl transferase ( tdt ) staining , but was without systemic involvement . 
 the patient was treated using cyclophosphamide , adriamycin , vincristine , and prednisolone ( chop ) , and achieved complete response ( cr ) at the first response assessment conducted after 3 chop cycles . 
 after an additional cycle of chop treatment , radiotherapy was administered at a total dose of 3,600 cgy over 4 weeks . at the 21-month follow - up , he had maintained cr . 
INTRODUCTION
CASE REPORT
DISCUSSION