Fig 1.
A. 3D image construction and analysis of the germinal center score. The solid component indicating a high-intensity area within the thymic tissues, and the fatty component indicating a low-density area within the adipose tissue around the thymus can be seen; 3D images were constructed, and the volume of the solid area (thymic tissue) was calculated; the total volume was considered as the volume resected by extended thymectomy (total volume = solid volume + fat volume). B. Thymic tissues around the fatty tissues resected by extended thymectomy fixed in formalin, cut at intervals of 1 cm, and embedded in paraffin; tissue sections prepared and then stained with hematoxylin and eosin (HE) for histological examination; the number of germinal centers was counted, and the area of thymic tissue was calculated using Image J software; the number of germinal centers per area of thymic tissue (pixel) (×10−6) was assessed, and the highest value was considered as the germinal center score.
Table 1.
Clinical characteristics of the study group.
Fig 2.
A. Pre- and post-surgery AChRab values. A significant improvement in the AChRAb levels can be seen after the operation when compared to the levels before the operation in each of the patients (paired t-test, p < 0.05). B. Difference between AChRab improvement rates for the pre-surgery PSL administration group (PSL(+)) and pre-surgery PSL, not administration groups (PSL(-)). Pre-surgery PSL received group was seven patients (we could not follow only one patient after surgery AChRab.); therefore, we analyzed six patients for PSL group. There is no significant difference in the AChRab between the pre- and post-surgery groups (unpaired t-test p = 0.501). C. Correlation between AChRab improvement rate and solid volume. There is no correlation between the AChRab improvement rate and solid volume. The white dots indicate the PSL (+) group, while the black dots denote the PSL(-) group (Spearman r = 0.21, p = 0.53).
Fig 3.
MG-ADL (activities of daily living scale) score (pre-surgery and post-surgery 1 year, 3 years).
Seven patients were administered PSL preoperatively (black dots: PSL(+)). The white dots denote those who were not administered PSL preoperatively (PSL(-)).
Fig 4.
A. Germinal center and solid volume, Solid/Fat ratio. The relationship between the number of germinal centers in the resected thymus and the solid volume of the thymus is seen in preoperative CT images. B. Germinal center and Solid/Fat ratio. The number of germinal centers correlate with the solid/fat ratio (Spearman r = 0.676, p = 0.0158). C. Germinal center score and pre PSL (+) group, pre PSL (-) group. The difference in the germinal center scores between the pre PSL (+) group and pre PSL (-) group is not significant (unpaired t-test, p = 0.585). D. Pre-surgery PSL amount (mg) and Germinal center score. There is no correlation between the pre-surgery PSL dose (mg) and the germinal center score (Pearson r = -0.36, p = 0.424).
Fig 5.
A. Solid volume and MG-ADL improvement—1 year after surgery. The MG-ADL improvement rates 1 year after the surgery do not correlate with the solid volume of the thymus (Pearson r = 0.398, p = 0.29). B. Solid volume and MG-ADL improvement—3 years after surgery. The MG-ADL improvement rates 3 years after the surgery do not correlate with the solid volume of the thymus (Pearson r = 0.09, p = 0.82).
Fig 6.
Solid volume and PSL dose-reduction extent.
The PSL dose-reduction extent correlates with the solid volume of the thymus (Pearson r = 0.70, p = 0.05). One patient (black dot) was administered PSL after the surgery. We included this patient in the analysis.