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A pathological evaluation is one of the most important methods for the diagnosis of malignant lymphoma. A standardized diagnosis is occasionally difficult to achieve even by experienced hematopathologists. Therefore, established procedures including a computer-aided diagnosis are desired. This study aims to classify histopathological images of malignant lymphomas through deep learning, which is a computer algorithm and type of artificial intelligence (AI) technology. We prepared hematoxylin and eosin (H&E) slides of a lesion area from 388 sections, namely, 259 with diffuse large B-cell lymphoma, 89 with follicular lymphoma, and 40 with reactive lymphoid hyperplasia, and created whole slide images (WSIs) using a whole slide system. WSI was annotated in the lesion area by experienced hematopathologists. Image patches were cropped from the WSI to train and evaluate the classifiers. Image patches at magnifications of ×5, ×20, and ×40 were randomly divided into a test set and a training and evaluation set. The classifier was assessed using the test set through a cross-validation after training. The classifier achieved the highest levels of accuracy of 94.0%, 93.0%, and 92.0% for image patches with magnifications of ×5, ×20, and ×40, respectively, in comparison to diffuse large B-cell lymphoma, follicular lymphoma, and reactive lymphoid hyperplasia. Comparing the diagnostic accuracies between the proposed classifier and seven pathologists, including experienced hematopathologists, using the test set made up of image patches with magnifications of ×5, ×20, and ×40, the best accuracy demonstrated by the classifier was 97.0%, whereas the average accuracy achieved by the pathologists using WSIs was 76.0%, with the highest accuracy reaching 83.3%. In conclusion, the neural classifier can outperform pathologists in a morphological evaluation. These results suggest that the AI system can potentially support the diagnosis of malignant lymphoma.

Peripheral T-cell lymphoma, not otherwise specified (PTCL-NOS) is cytologically and phenotypically heterogeneous. Retinoic acid-related orphan receptor-γt (RORγt) is a transcription factor that regulates the differentiation of naive CD4+ helper T cells to Th17 cells. In the present study, we immunohistochemically confirmed the expression of RORγt in PTCL-NOS. Pathological and clinical investigations were performed for 170 cases of PTCL-NOS. RORγt-positive cases accounted for 17.6% (30/170) of the total cases, and they showed a significantly higher frequency of CD8 positivity (P = .033), lower counts of white blood cells (P = .030) and neutrophils (P = .039) in the peripheral blood, higher levels of hypergammaglobulinemia (P = .031), a higher frequency of a complete response (P = .009), and a tendency for a lower International Prognostic Index (P = .061) and better overall survival (P = .0806). These results suggest that RORγt-positive PTCL-NOS could be a subpopulation of PTCL-NOS. Further research associated with this genomic abnormality at the transcriptional level is needed to confirm the results of this study.