萎缩Atrophy · 脾脏 · 免疫系统 · NTP ntp-0044

Comment：
Atrophy can affect the white pulp and/or red pulp compartments of the spleen. Lymphocyte atrophy of the white pulp is characterized by a loss of lymphocytes in the T-cell areas (periarteriolar lymphatic sheaths [PALS]) and/or B-cell areas (follicles, germinal centers, marginal zones). Depending on severity, this can result in a decrease in overall PALS cellularity/area or follicle number/size ( Figure 1 and Figure 2 , arrows). Red pulp atrophy is characterized by a decrease in the relative amount of red pulp components, including hematopoietic cells ( Figure 3 and Figure 4 , arrows). Splenic atrophy can be observed as a spontaneous change in older rats and mice and typically involves red and white pulp compartments. Atrophy can also occur as a direct treatment-related effect or can be an indirect effect secondary to weight loss or reduced body weight gain.

Recommendation：
Whenever present, atrophy of the spleen should be diagnosed and assigned a severity grade. A site modifier should be included in the diagnosis to indicate whether the red pulp or the white pulp is affected. If both compartments are involved, diagnose "Spleen - Atrophy." If splenic atrophy is present as a secondary lesion, as in the case of neoplasia, it need not be recorded but should be described in the pathology narrative.