blastic plasmacytoid dendritic cell neoplasm ( bpdcn ) is a rare hematologic malignancy that typically involves the skin , lymph nodes , the peripheral blood and the bone marrow . this tumor expresses cd4 and cd56 with no obvious evidence of b- or t - cell differentiation . since adachi et al . ( 1 ) first described cd4+/cd56 + hematodermic neoplasm in 1994 , several individual cases or small groups of cases of this disease have been reported . relapse frequently occurs within 6 months or less from the initiation of chemotherapy and most patients experience rapid progression that is refractory to conventional chemotherapy . we report here on a case of advanced bpdcn that was initially misdiagnosed as cutaneous lupus erythematosus . a 67-year - old man with a past history of gout had complaints of non - itching painless skin lesion on the back and it was spreading to the whole trunk , face , arms and thighs for the previous 3 months . this lesion initially presented as a dusky erythematosus patch with indurations on the dorsal area , and it eventually grew and spread . skin examination showed multiple hyperemic nodules and plaques on the face and trunk ( fig . a biopsy specimen taken from the facial skin lesion revealed atrophy of the epidermis , a flattened stratum malpighii , small numbers of necrotic keratinocytes and eosinophilic swelling of the dermal collagen fibers , as well as a perivascular and interstitial lymphohistiocytic infiltration in the entire dermis ( fig . 2 ) . on the basis of positive imunophenotyping for cd3 and cd20 , the negative imunophenotyping for cd56 and the presence of a mixed reactive lymphocytic infiltration of t and b - cells , a diagnosis of lupus erythematosus was made . the hemoglobin value was 12.2 g / dl , the platelet count was 83,000/l and the white blood cell count was 22,900/l with 3% atypical lymphocytes and 7% blasts . the serum levels of lactate dehydrogenase , uric acid and creatinine were increased ( 1,580 iu / l , 10.5 mg / dl and 1.56 mg / dl , respectively ) . marrow aspiration disclosed that blasts comprised 89% of the mononuclear cells and the blasts were of variable size with agranular cytoplasm , and they were positive for cd2 , cd3 , cd4 , cd5 , cd7 , cd45 , cd56 , and hla - dr , and they were negative for myeloperoxidase , terminal deoxynucleotidyl transferase , cd3 , cd8 , cd10 , cd13 , cd14 , cd19 , cd20 , cd33 , cd34 , and cd61 . cytogenetic analysis revealed a karyotype of 46 , xy , add(9)(p24 ) , del(11)(q22 ) . repeated biopsy from the left cheek revealed a diffuse lymphoid infiltrate of cells with medium sized nuclei , and the cells were positive for cd4 , cd43 , cd56 and cd99 ( fig . immunostaining for cd3 , cd6 , cd8 , cd20 , cd30 , t - cell intracellular antigen-1 , myeloperoxidase , and terminal deoxynucleotidyl transferase was either weak or negative ( fig . epstein - barr virus ( ebv ) was not detected by rna in situ hybridization , nor were ebv antibodies detected . a study of t cell receptor gene rearrangement was not performed because the patient did not give informed consent . computed tomography of the chest and abdomen showed multiple lymphadenopathies in both axillae , the lower neck , the right lower paratracheal area , the lower anterior mediatsinum , the left gastric area , the pericholedocal site and the celiac axis area . the patient received six courses of multidrug chemotherapy consisting of ifosphamide , methotrexed , etoposide , prednisolone and l - asparaginase , and the patient achieved a partial remission . bpdcn is a rare hematopoietic malignancy , and there has been few data about its incidences . spanish study ( 2 ) reporting the overall incidence of bpdcn among all acute myeloid leukaemia and non - hodgkin 's lymphoma was 0.76% and 0.27% , respectively and japanese study ( 3 ) reporting a 6.33% incidence of this malignancy among natural killer ( nk ) cell - lineage neoplasm . in korea , a total of 17 cases of bpdcn have been reported as single cases or as clusters of cases . among these cases , 4 cases ( 4 ) were reported in 2005 and 10 new cases ( 5 ) were reported in 2007 , and all of these patients died except for three patients who had disease confined to skin . since this disease entity was first described ( 1 ) in 1994 , the nomenclature has changed several times according to the expanded knowledge of this malignancy . the naming of blastic nk cell lymphoma / leukemia was based on the distinct cytology and nk cell origin suggested by the cd56 expression . however , the cd4 positivity and the lack of expressing other nk - lineage markers in most cases cast doubt on its derivation from nk precursors , and hence the french study group on cutaneous lymphoma ( 6 ) called it agranular cd4+/cd56 + hematodermic neoplasm . the world health organization - european organization for research and treatment of cancer ( who - eortc ) consensus classification agreed ( 7 ) because of the disease 's uncertain lineage . on further study , chaperot et al . ( 8) proposed that the plasmacytoid dendritic cell ( pdc ) might be the normal counterpart of this disease in 2001 . on the studies using functional , immunohistochemical and molecular tools , the expressions of the interleukin 3 receptor -subunit and blood dendritic cell antigen-2 were compatible with a plasmacytoid dendritic cell origin , and the authors of those studies named the disease bpdcn ( 9 ) . the name bpdcn was enlisted in the 2008 who classification of tumors of the hematopoietic and lymphoid tissues . although the origin of this malady has been defined , the oncogenesis at the molecular level has yet to be clarified . histopathologically , bpdcn is characterized by a dense monomorphous infiltration of medium - sized blastoid cells that are positive for cd4 , cd56 , cd123 and tcl-1 . ( 10 ) evaluated 33 patients with a proven diagnosis of bpdcn and they found that the cutaneous lesions of bpdcn were quite variable . most of their cases ( 80% ) presented with nodular / diffuse infiltrates in the entire dermis , fewer cases ( 20% ) presented with relatively small , perivascular or interstitial aggregates of cells , and some cases resembled the picture of a cutaneous inflammatory disorder . the tumor cells in the latter cases were found with reactive lymphocytes , and this made the diagnosis of bpdcn difficult and dicey . in our case , the skin lesion at first biopsy was suggestive of reactive change rather than malignancy . the second biopsy revealed an extensive diffuse lymphocytic infiltration that was positive for cd4 , cd43 , cd56 and cd99 , which is quite a different finding from the first one and it definitely favored the diagnosis of bpdcn . this is certainly a lesson that both clinicians and pathologists should be aware of the atypical presentations of bpdcn from the onset . the histopathologic findings of discoid lupus erythematosus are typified by an interface dermatitis involving the hair follicles and epidermis , and this is accompanied by a moderate to heavy superficial , deep perivascular and periappendageal lymphocytic infiltration . plasmatoid dendritic cells are known to play an important role ( 11,12 ) in the pathogenesis of lupus erythematosus and these cells produce type i interferon . ( 13 ) showed that a cutaneous plasmatoid dendritic cell infiltration is a hallmark of lupus erythematosus . although it is thought that bpdcn originates from pdcs , there has been no report of bpdcn in the setting of lupus . bpdcn mainly occurs in older patients , although it can occur at any age , including the pediatric period . it affects males more frequently than females ( 12 ) at a proportion of roughly 3:1 . it frequently involves multiple sites with a predilection for skin , and this is followed by bone marrow , peripheral blood and lymph nodes . the skin lesions tend to be localized at the onset and then they become multiple or more generalized during the course of disease , and overt leukemia is the usual finding in advanced cases or there is relapse after therapy . frequent chromosomal aberrations in various sites have been reported for this disease , including chromosomal losses on 5q , 6q , 12p , 13q and chromosomes 9 and 15 , as well as deletion of regions on 4q34 , 9p13-p11 , pq12-q34 and 13q12-q31 . our case demonstrated an abnormal karyotype of 46 , xy , add(9)(p24 ) , del ( 11)(q22 ) . the comparative genomic hybridization performed in the 4 cases reported in korea ( 5 ) showed amplification of 11q12.31 in all 4 cases and 12q13.11 in three . the clinical course of bpdcn is aggressive and generally dire at best , with the median survival time being 12 - 24 months . although there is no consensus on the optimal treatment for this neoplasm , a systemic treatment should be started at the outset regardless of whether the disease is localized or disseminated . the clinical course in most cases has been characterized by an initial response to chemotherapy followed by relapse and subsequent death . as the outcomes of many therapeutic attempts have been reported to be quite variable , there is no standard treatment for bpdcn . usually the duration of a response to topical steroid , single agent chemotherapy , radiotherapy and polychemotherapy like chop ( cyclophosphamide , doxorubicin , vincristine , prednisone ) or hypercvad ( cyclophosphamide , vincristine , doxorubicin , dexamethasone alternating with high dose methotrexate and high dose cytarabine ) has been reported to be brief . pralatrexate was anecdotally reported to be active as a salvage treatment ( 14 ) although its impact on the clinical course looked negligible . in the face of the extremely poor outcome of conventional chemotherapy and radiation therapy , dalle et al . ( 15 ) asserted that only stem cell transplantation can significantly prolong survival regardless of the initial extent of disease . although our patient has shown a partial response to six cycle of chemotherapy , his ultimate prognosis looks grim . our case taught us a lesson that bpdcn should be considered in the differential diagnosis of skin rashes that are refractory to treatment . although we could not identify pdcs in skin on the first biopsy in our case , their accumulation has been described in several inflammatory cutaneous conditions ( 12 ) such as systemic lupus erythematosus , psoriasis , lichen planus and contact dermatitis . given its easy accessibility and relative safety , we advocate that repeated skin biopsy should be performed in every case of unusual skin lesion .