The case is Courtesy of dr.R.Meškauskas. Unfortunatelly we have not CD123 for final confirmation (flow only). The case is the first one there.  
 
86 yrs old female with clinical diagnosis "B cell lymphoma" was biopsied (skin nodule from back).  
HISTORY: The nodule in the back was noticed in 2009 July. The non-itching eruption progressed and covered back skin, thorax and shoulders.  
CLINICALLY: 2-7 cm bluish nodules in the back skin.  
Additional threpine biopsy was taken.  
FLOW CYTOMETRY: CD123+, CD45+dim, CD33+dim, CD56+, CD4+dim, CD43+, HLA-DR+, CD13-, CD34-, CD117-, cMPO-, cCD3-, cCD79a- (interpretation: blastic tumor, most probable blastoid dendritic cell tumor).  
During IH stainning ADDITIONAL skin biopsy was taken from femoral skin with clinical diagnosis "dysplastic nevus".  
 
HISTO:  
SKIN 1 (back): blastoid "leukaemic" infiltrate with IH: LCA+; CD4+; Bcl2+; CD20/Cd79a/Pax5/CD3/CD5/CD2(-), CD30/CD10/CD5/CD23/CD21(-), Bcl6/CyclinD1/Ig Kappa/Ig Lambda(-), CD68/MPO/CD34/Tdt/CD56/S100/Cd56/Cd117(-).  
SKIN 2 MELANO (femur): 1) Identical "blastoid" infiltrate: LCA+, CD4+, Bcl2+ (Ki67+ 40%): 2) MelanA+ pagetoid spread of Melanoma in situ within mixt dysplastic nevus.  
BM: erythroid hyperplasia, architectural distortion with interstitial infiltrate of NASDE(-) "blastoid cells" 10% with immunophenotype: Bcl2+; CD34/CD117/TdT(-), CD4(-)(? technical reasons?).  
 
DIAGNOSIS: 1. Blastoid dendritic cell ("hematodermic") tumor: multifocal spread in skin (back, femur) and bone marrow. 2. Melanoma in situ (femoral skin) in mixt dysplastic nevus.  
QUEST: Interstitial vs nodular infiltrates in DC2 tumors in the skin.  
Thank you for participating.

tzankov 2010-03-15 10:14	I agree with you diagnoses. There is a "leukameia cutis", which could be classified according to the makers analyzed at least as acute leukemia of ambigous lineage DD blastic plasmocytoid dendritic cell neoplasia. The melanocytic lesion is at least melanoma in situ. The bone marrowis infiltrated by the former tumor. Could you add CD68 and CD45 from the bone marrow?
ugnius 2010-03-15 10:46	Thanx. Unfortunatelly CD68 was negative even in the skin. LCA I will append later (it was not stained in BM).
hurwitz 2010-03-20 19:47	I agree with your diagnoses, with the reservation that I am not convinced about the melanoma being still in situ.   I would also like to see stains for CD56 and CD 4 on the bone marrow biopsy.
diane.c.farhi 2010-03-22 16:36	We have two processes, melanocytic and blastic. Regarding the melanocytic lesion, I consulted one of our dermatopathologists, who agreed with the previous comments. He diagnosed it as melanoma-in-situ, cannot exclude microinvasion. Regarding the blastic process, it fits well with primary cutaneous CD4+/CD56+ hematodermic neoplasm (formerly blastic NK-cell lymphoma), involving both skin and bone marrow. I feel confident about this diagnosis. I don't know whether this malignancy shows bcl-2 protein overexpression, but it is possible, as this finding is not lineage-specific for B cells.
ugnius 2010-05-24 15:45	The case was sent to external consultation to dr.A.Tzankov and dr.S.Dirnhofer (Basel, Swiss). Additional IH skin: DC2 tumor CD123+; TdT+ focal; CD56+. Ki67 fraction about 25%.   FINAL DIAGNOSIS: BLASTIC PLASMACYTOID DENDRITIC CELL NEOPLASM; INFILTRATION IN THE SKIN (BACK AND FEMUR) AND BONE MARROW (7%). MELANOMA IN SITU IN THE FEMORAL SKIN.   Additional photos: courtesy of dr.A.Tzankov. The case was presented in 7th Baltic Hematology Congress, Tartu, Estonia, 2010 05 20-22.
tzankov 2010-05-25 07:00	After reviewing this case at the microscope and with the information on the expression of CD123, TdT and CD56, we can close the case now. The final diagnosis is     BLASTIC PLASMACYTOID DENDRITIC CELL NEOPLASM WITH INFILTRATION OF THE SKIN (BACK AND FEMUR) AND THE BONE MARROW (7%).     MELANOMA IN SITU OF THE FEMORAL SKIN.     Thanks to Ugnius for this case and to all the participants for their comments.
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