Hypophysitis superimposed on a non-functioning pituitary adenoma: diagnostic clinical, endocrine, and radiologic features.

Pituitary adenomas are common neoplasms requiring medical and/or surgical treatment when associated with hormonal hypersecretion. Treatment of non-functioning pituitary adenomas is necessary when symptoms of mass effect or hormonal deficits occur. However, therapeutic options, including surgical resection and/or radiotherapy, can be associated with significant complications. Hence, it is important to consider disorders that could present in a similar manner to pituitary adenomas, for which surgery is not the indicated therapeutic approach. We describe herein a 38-yr-old woman who presented with a pituitary lesion that was considered to be a non-functioning pituitary adenoma. Due to lack of hormonal deficits and/or compression of adjacent structures, we opted for conservative management and followup with consecutive magnetic resonance imaging. Fifteen months after initial diagnosis, considerable enlargement of the lesion was noted, extending mainly superiorly and indenting the optic chiasm. Repeated endocrine investigation revealed partial anterior pituitary insufficiency. The patient underwent trans-sphenoidal resection of the pituitary lesion; histology revealed a null cell pituitary adenoma and lymphocytic hypophysitis (LYH) of the non-neoplastic adenohypophysial gland. Post-operatively, complete anterior and partial posterior pituitary insufficiency developed. This case illustrates the effects of new-onset LYH in a patient with a pre-existing non-functioning pituitary adenoma. Being aware of this rare possibility is important, as enlargement of the pituitary lesion may not be caused by expansion of the preexisting tumor, but by the onset of LYH of the nonneoplastic pituitary tissue.