JC EH lin xp ematopathol Original article INTRODUCTIONBlastic plasmacytoid dendritic cell neoplasm (BPDCN) is a relatively rare hematological malignancy, 1 accounting for 0.44% of all hematological malignancies and 0.7% of all cutaneous lymphomas.2 BPDCN is a clinically aggressive tumor derived from the precursors of plasmacytoid dendritic cells (pDC).1 It usually occurs at the age of 50-70 and is rare in pediatric patients; the ratio of male to female patients is 2.5-2.7:1, and the median survival is 12-14 months. 1-4The clinical features and evolution of BPDCN are rather homogenous and categorized into dermatopathic (>90% of cases) and leukemic patterns. 5 The dermatopathic pattern is characterized by a deceptive indolent onset dominated by skin lesions, which is the prominent and only detectable clinical feature in nearly 50% of patients, followed by tumor dissemination. Conversely, the leukemic variant is characterized by an elevated white blood cell count, circulating neoplastic cells, and massive bone marrow (BM) infiltration. Pure leukemic presentation is very rare (7% of 756 cases) and is mostly associated with multiple skin lesions. Other manifestations are related with tumor infiltration into the lymph nodes (localized and generalized lymphadenopathy), spleen, and liver. Notably, BPDCN can be precisely diagnosed by the immunohistochemical scoring system using CD4, CD56, and Blastic plasmacytoid dendritic cell (pDC) neoplasm (BPDCN) is a relatively rare hematological malignancy with significantly complex clinicopathological features that are still unclear. This study aimed to analyze the clinicopathological data of BPDCN and evaluate immunohistochemical detection of minimal bone marrow (BM) involvement. In this study, we examined skin and BM lesions from 6 patients with BPDCN. Neoplastic cells tested positive for CD303 (polyclonal, 100%; monoclonal, 40%) in the skin lesions and for CD303 (polyclonal, 100%; monoclonal, 67%) in the BM clots. Although immunostaining of CD4, CD56, CD123, CD303, and TCLl detected minimal BM involvement in 3 patients, morphological identification was challenging in the BM clots stained with hematoxylin-eosin. In conclusion, our results demonstrate the significance of observing BM smears to detect neoplastic cells and that immunohistochemical examination, including CD303 antibodies, is useful to detect minimal BM involvement. This study is the first to report the expression of thymic stromal lymphopoietin (TSLP) and its receptor in BPDCN cells. Therefore, the TSLP/TSLP receptor axis may be associated with the proliferation of BPDCN, and consequently, the survival of patients.

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Immune checkpoint inhibitors blocking the interaction between PD-1 and PD-L1 are revolutionizing the cancer immunotherapies with durable clinical responses. Although high expression of PD-L1 in tumor tissues has been implicated to correlate with the better response to the anti-PD-1 therapies, this association has been still controversial. In this study, to characterize immune microenvironment in tumors, we examined mRNA levels of immunerelated genes and characterized T cell repertoire in the tumors of 13 melanoma patients before and after nivolumab treatment. We found that, in addition to the PD-L1 (P ¼ 0.03), expression levels of PD-1 ligand-2 (PD-L2), granzyme A (GZMA) and human leukocyte antigen-A (HLA-A) in the pre-treatment tumors were significantly higher (P ¼ 0.04, P ¼ 0.01 and P ¼ 0.006, respectively) in responders than in non-responders. With nivolumab treatment, tumors in responders exhibited a substantial increase of CD8, GZMA and perforin 1 (PRF1) expression levels as well as increased ratio of TBX21/GATA3, suggesting dominancy of Th1 response. The scoring system using three possible biomarkers