Methotrexate (MTX) carries a risk of lymphoproliferative disorders (LPDs), but MTX-associated LPDs (MTX-LPDs) can resolve spontaneously after MTX withdrawal. However, the precise clinicopathologic features of MTX-LPD remain unclear. We aimed to investigate the clinicopathologic characteristics, outcomes, and prognostic factors for histologic types of MTX-LPD. Paraffin-embedded tissue samples of 219 patients with MTX-LPD were analyzed. In total, 30,33,106, and 26 had reactive lymphoid hyperplasia (RH), polymorphic-LPD (Poly-LPD), diffuse large B-cell lymphomas (DLBCLs), and classic Hodgkin lymphoma (CHL), respectively. The clinicopathologic features of RH, Poly-LPD, DLBCLs, and CHL were as follows: extranodal involvement: 13.8% (4/29), 36.4% (12/33), 69.5% (73/105), and 15.4% (4/26); Epstein-Barr virus encoded RNA positivity: 55.2% (16/29), 71.9% (23/32), 45.3% (48/106), and 76.9% (20/26); necrosis: 0% (0/29), 51.5% (17/33), 34.3% (36/105), and 12.0% (3/25); and Hodgkin Reed-Sternberg-like cells: 17.2% (5/29), 50% (14/28), and 19.8% (21/106). The median duration from MTX withdrawal to the time of disease regression was 10.4, 3.0, 4.2, and 2.7 months for RH, Poly-LPD, DLBCLs, and CHL. After MTX withdrawal, progression-free survival was the greatest for RH, followed by for Poly-LPD, DLBCL, and CHL (all P<0.05). Overall survival did not differ significantly between the groups. On univariate analysis, the predictive factors for progression-free survival included plasma cell infiltrate for CHL, eosinophil infiltrate, age above 70 years, and extensive necrosis for Poly-LPD, while they were Epstein-Barr virus encoded RNA positivity and International Prognostic Index risk for DLBCL on multivariate analysis. In conclusion, histologic categorization and histology-specific factors could be useful for predicting MTX-LPD progression after MTX withdrawal.

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Peripheral T-cell lymphoma (PTCL), not otherwise specified (PTCL-NOS) is among the most common disease subtypes of PTCL, one that exhibits heterogeneous clinicopathological features. Although multiple disease-stratification models, including the cell-of-origin or gene-expression profiling methods, have been proposed for this condition, their clinical significance remains unclear. To establish a clinically meaningful stratification model, we analyzed gene-expression signatures of tumors and tumor-infiltrating immune cells using the nCounter system, which enables accurate quantification of low abundance and/or highly fragmented transcripts. To do so, we assessed transcripts of 120 genes related to cancer or immune cells using tumor samples from 68 newly diagnosed PTCL-NOS patients and validated findings by immunofluorescence in tumor sections. We show that gene-expression signatures representing tumor-infiltrating immune cells, but not those of cancerous T cells, dictate patient clinical outcomes. Cases exhibiting both B-cell and dendritic cell (DC) signatures (BD subgroup) showed favorable clinical outcomes, whereas those exhibiting neither B-cell nor DC signatures (non-BD subgroup) showed extremely poor prognosis. Notably, half of the non-BD cases exhibited a macrophage signature, and macrophage infiltration was evident in those cases, as revealed by immunofluorescence. Importantly, tumor-infiltrating macrophages expressed the immune-checkpoint molecules programmed death ligand 1/2 and indoleamine 2, 3-dioxygenase 1 at high levels, suggesting that checkpoint inhibitors could serve as therapeutic options for patients in this subgroup. Our study identifies clinically distinct subgroups of PTCL-NOS and suggests a novel therapeutic strategy for 1 subgroup associated with a poor prognosis. Our data also suggest functional interactions between cancerous T cells and tumor-infiltrating immune cells potentially relevant to PTCL-NOS pathogenesis.

Two years of continuous in situ measurements of Arctic low‐level clouds have been made at the Mount Zeppelin Observatory (78°56′N, 11°53′E), in Ny‐Ålesund, Spitsbergen. The monthly median value of the cloud particle number concentration (Nc) showed a clear seasonal variation: Its maximum appeared in May–July (65 ± 8 cm−3), and it remained low between October and March (8 ± 7 cm−3). At temperatures warmer than 0 °C, a clear correlation was found between the hourly Nc values and the number concentrations of aerosols with dry diameters larger than 70 nm (N70), which are proxies for cloud condensation nuclei (CCN). When clouds were detected at temperatures colder than 0 °C, some of the data followed the summertime Nc to N70 relationship, while other data showed systematically lower Nc values. The lidar‐derived depolarization ratios suggested that the former (CCN‐controlled) and latter (CCN‐uncontrolled) data generally corresponded to clouds consisting of supercooled water droplets and those containing ice particles, respectively. The CCN‐controlled data persistently appeared throughout the year at Zeppelin. The aerosol‐cloud interaction index (ACI = dlnNc/(3dlnN70)) for the CCN‐controlled data showed high sensitivities to aerosols both in the summer (clean air) and winter–spring (Arctic haze) seasons (0.22 ± 0.03 and 0.25 ± 0.02, respectively). The air parcel model calculations generally reproduced these values. The threshold diameters of aerosol activation (Dact), which account for the Nc of the CCN‐controlled data, were as low as 30–50 nm when N70 was less than 30 cm−3, suggesting that new particle formation can affect Arctic cloud microphysics.

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