Pituitary macroadenoma - necrotic
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A mass expands the pituitary fossa. It is centrally of fluid signal with thick nodular peripheral contrast enhancing tissue. The optic chiasm is pushed superiorly and distorted. The mass also invades the right cavernous sinus.
This patient went on to have a transphenoidal resection.
Most of the tissue fragments are composed of uniform cells with round nuclei and abundant granular cytoplasm arranged in solid sheets and papillary structures. Rare mitotic figures are identified. Small fragments of atrophic adenohypophysis are also present. Immunohistochemistry for pituitary hormones shows the tumor to have moderately intense, focal positivity for LH.
Final diagnosis: pituitary adenoma (focal reactivity for LH).
Although most macroadenomas are solid, cystic change due to necrosis or prior hemorrhage is not infrequently seen.