Lymph Node - Lymphatic Sinus, Ectasia
Lymphatic sinus ectasia can involve the subcapsular ( Figure 1 , arrow), paracortical, or medullary ( Figure 2 , arrow) sinuses of lymph nodes in rats and mice. Sinuses are enlarged relative to the size of the lymph node, are lined by lymphatic endothelium, and may be filled with pale eosinophilic/amphophilic material (presumably lymph). Few intraluminal lymphocytes, macrophages, and/or erythrocytes may be present. Lymphatic sinus ectasia may be related to treatment or dose; however, this lesion can also be seen in control and aging rodents, particularly in the mesenteric or mediastinal lymph nodes. Diffuse sinus ectasia may also be associated with lymphoid atrophy. Lymphatic sinus ectasia should be differentiated from blood vessel angiectasis in the lymph node, which is characterized by the dilatation and congestion of thin veins within the cortex, medulla, capsule, hilus, or surrounding connective tissue. Previous terms for lymphatic sinus ectasia are "lymphangiectasia," "lymphatic cysts," "cystic lymphatic ectasia," and "sinus dilatation."
Lymphatic sinus ectasia should be diagnosed and assigned a severity grade. If this lesion is present as a component of lymphoid atrophy, atrophy should be diagnosed, and the lymphatic sinus ectasia and any other associated lesions should be described in the narrative.
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