Histology 

Sections show multiple fragments of a pituitary adenoma, sclerotic stroma, and a few bony chips. The tumor cells are uniform and are laid in sheets and acini. The cytoplasm is amphophilic. There are no atypical features identified. The reticulin stain confirms the loss of acinar structure. No normal pituitary tissue is identified in the vicinity of the tumor. Immunohistochemistry for ACTH, prolactin, growth hormone, TSH, FSH and LH is negative.

Final diagnosis: Nonfunctioning (null cell) pituitary adenoma.