Osseous metaplasia in a growth hormone-secreting pituitary adenoma

A case of growth hormone-secreting adenoma of the pituitary gland showing o sseous metaplasia is described in a 56-year-old acromegalic female. The tum or was composed of nests of densely granulated cells separated by and inter mixed with calcifications, trabeculae of mature bone and fat. Calcification s are seldom found in pituitary adenomas. In rare instances, calcium deposi ts can be prominent enough to lead to the formation of pituitary stones and bone which replace the entire tumor mass. Analogously with metaplastic men ingiomas, we propose using the term metaplastic adenoma to define cases wit h osseous metaplasia in order to distinguish between lesions containing bon e from the more frequently seen calcified adenomas.