Spontaneous regression of a solitary necrotic nodule of the liver

Solitary necrotic nodules of the liver occur rarely. Although these nodules are usually benign, they are surgically removed in most cases because they cannot be differentiated from malignant lesions. To date, the natural history of solitary fibrous nodules remains unclear. We present the case of an incidentally detected hepatic mass (diameter 2 cm) in a 35-year-old man. The hepatic mass was diagnosed as a solitary necrotic nodule by liver biopsy. Follow-up radiologic examination revealed that the solitary necrotic nodule had spontaneously regressed. This is the first report on the natural course history of a solitary necrotic nodule

The urbilaterian brain revisited: novel insights into old questions from new flatworm clades

Flatworms are classically considered to represent the simplest organizational form of all living bilaterians with a true central nervous system. Based on their simple body plans, all flatworms have been traditionally grouped together in a single phylum at the base of the bilaterians. Current molecular phylogenomic studies now split the flatworms into two widely separated clades, the acoelomorph flatworms and the platyhelminth flatworms, such that the last common ancestor of both clades corresponds to the urbilaterian ancestor of all bilaterian animals. Remarkably, recent comparative neuroanatomical analyses of acoelomorphs and platyhelminths show that both of these flatworm groups have complex anterior brains with surprisingly similar basic neuroarchitectures. Taken together, these findings imply that fundamental neuroanatomical features of the brain in the two separate flatworm groups are likely to be primitive and derived from the urbilaterian brain