The patient went on to have a transphenoidal resection.
MICROSCOPIC DESCRIPTION: Sections show small fragments of dense fibrous tissue with scattered clusters and distorted acini of functioning pituitary cells (GH and Prolactin positive). There is infiltration and destruction of pituitary acini by CD3, CD4 and CD8 positive T-cells. Small sheets of necrotic tissue are seen adjacent to the tissue. Occasional small clusters of histiocytes are identified but no clearly discernable granulomas are seen. No mycobacteria or fungi are identified on ZN and PAS stains. There is no evidence of malignancy.
DIAGNOSIS: Features favouring an autoimmune lymphocytic hypophysitis.