The fine neuroanatomy of mood disorders and suicide is a relatively recent field of investigation. Together with neuroimaging, molecular biology and biochemistry, histological analyses of post-mortem brain regions implicated in mood regulation allow gaining a better understanding of the cellular and molecular mechanisms underlying major depression and suicide. In this article, the author discusses recent studies conducted in his laboratory on the fine neuroanatomy of the anterior cingular cortex (ACC). In particular, he presents data showing that ACC white matter fibrous astrocytes are hypertrophic in depressed suicides compared to matched sudden-death controls. These data are interpreted in the context of the neuroimmune hypothesis of major depression and suicide.