Squamous metaplasia following necrosis of the adenohypophysis and of a chromophobe adenoma of the pituitary.

Two cases of pituitary necrosis was presented, one occurring post partum in an otherwise normal gland, the other in a large chromophobe adenoma. In both cases the necrotic tissue became surrounded by squamous epithelial nests that developed through metaplasia from glandular cells of the adenohypophysis and adenoma cells respectively. The squamous elements were seen 6 days after the clinical events leading to pituitary necrosis in the first case and 20 days after pituitary apoplexy (hemorrhagic necrosis of an adenoma) in the second case. In contradistinction to the commonly found squamous nests which are usually located in the pars tuberalis and presumably develop through a slower process, the changes in the present two cases indicate that squamous metaplasia can develop quite rapidly at the margins of a necrotic process of the pituitary, either deep in the gland as in case 1 or occupying the entire circumference of a necrotic tumor as in case 2.