abnormal spleen white pulp morphology abnormal spleen marginal sinus morphology MP:0002363 MPheno.ontology Note that there is no consensus in the literature about which compartments constitute the white pulp or the ramifications of the microvasculature. In addition, notable differences exist between humans and rodents. In this ontology, the marginal sinus (which may not exist in human) has been included as part of the white pulp. The perifollicular zone, which is present in human and not rodents, may be the functional equivalent of the marginal sinus in rodents. abnormal splenic marginal sinus morphology any structural anomaly of the border region surrounding the spleen B cell follicles and the periarteriolar lymphoid sheath (PALS) that separates it from the marginal zone that mediates lymphocyte entry into the white pulp from the blood