Microglia in teratomas.

Using an ammoniacal silver nitrate stain, we have demonstrated typical microglial cells in three teratomas. Microglia appeared identical to their counterparts in the mature human brain, both resting and slightly hypertrophic types being present in differentiated nervous tissue, which also comprised astrocytes, neurones and ependyma. The implications of the presence of microglia with ectodermal derivatives in teratomas are discussed.