BPDCN is suggested by a biopsy of skin lesions which reveals the infiltration by medium-sized blast (i.e. immature)<unk> s into the dermis while sparing the epidermis. These<unk> s exhibit irregular nuclei, fine chromatin, and at least one small nucleolus. Such<unk> ells may also be observed in the circulation, bone marrow, or other tissues and suggest BPDCN. However, the diagnosis of this disease requires determination that these<unk> s are pDC<unk> ells rather than AML, T-cell lymphoblastic lymphoma (TCLL), or aggressive NK-cell leukemia (NKL)<unk> ells. Various studies have offered similar but not identical criteria to make this determination. All studies agree that pDC should have a typical<unk>  morphology and express a particular profile of marker proteins as detected by immunoassay and/or flow cytometry. However, the studies disagree on which marker proteins to profile. One study's profile assayed 1) CD4, CD56, CD123 (i.e. Interleukin-3 receptor, and TLC1, which are expressed on 80-100% of pDC but uncommon on AML, TCLL, or NKL blasts); 2) CD2AP and CLEC4C which are unique to pDC; and 3) myeloperoxidase, lysozyme, CD34, CD14, CD11c, and CD163 which are unique to AML, TCLL, or NKL blasts. Two other studies recommended assaying somewhat different sets of marker proteins.
Blastic plasmacytoid dendritic cell neoplasm
Congenital self-healing reticulohistiocytosis
Nodal marginal zone B cell lymphoma
Angioimmunoblastic T-cell lymphoma
Mature T-cell lymphoma
Peripheral T-cell lymphoma
Precursor T-lymphoblastic lymphoma
Pleomorphic T-cell lymphoma